Search
Submit Manuscript
1.6CiteScore
Advanced Search
MAP  >  Ornamental Plant Research
2023 Volume 3
Article Contents
Abstract
Introduction
Materials and methods
Materials
Preparation of mixed surimi samples
Rheological characteristics of mixed surimi samples
Apparent viscosity
Dynamic rheological behavior
Strength of mixed surimi gels
Textural properties of mixed surimi gels
Cooking loss of mixed surimi gels
Low-field nuclear magnetic resonance (lf-nmr) of mixed surimi gels
Color difference of mixed surimi gels
Scanning electron microscopy (sem) of mixed surimi gels
Thiobarbituric acid-reactive substances (tbars) determination
Statistical analysis
Results and discussion
Rheological properties of surimi gels
Steady-state shear properties
Dynamic elastic properties during gelation
Strength of surimi gels
Textural properties of surimi gels
Cooking loss of mixed surimi gels
Color of surimi gels
Changes in moisture distribution of surimi gels
Scanning electron microscopy of surimi gels
Thiobarbituric acid-reactive substances (tbars) determination
Conclusions
Author contributions
Data availability
Acknowledgments
Conflict of interest
Supplementary information
Rights and permissions
References
About this article
Next Previous
ARTICLE   Open Access    

Identification and characterization of class E genes involved in floral organ development in Dianthus chinensis

  • 1.

    National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, China

  • 2.

    Guangdong Laboratory for Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, Guangdong, China

  • # These authors contributed equally: Xiaoni Zhang, Quanshu Wu

More Information
  • The SEPALLATA (SEP) gene, as a 'glue' for the 'floral quartets model', plays an important role in floral organ development by forming tetramers with class A-, B-, and C- genes. The functional differentiation of class E genes has been reported in different species. Carnation (Dianthus spp.) is a world-famous economic flower that has been extensively used in landscaping, but the roles of SEP genes in carnation are unclear. Here, we found that the class E genes of D. chinensis cultivar 'L' showed different expression patterns during floral organ primordium development by transcriptome analysis. Combined with quantitative real-time PCR, its tissue and specific stage expression patterns were also different in different subclades. In addition, a yeast two-hybrid experiment was carried out to explore the interaction patterns of class E genes with other class A-, B-, and C- genes. Only DcSEP3s and DcSEP4s proteins interacted with all three classes of A-, B-, and C- proteins, and interestingly, is that DcSEP3-1 only interacted with the DcAP1 protein of class A, while the DcSEP3-2 protein only interacted with DcFUL1. Transgenic experiments showed that overexpression of DcSEP3-2 genes in Arabidopsis resulted in early flowering, smaller rosettes, dwarfism and abnormal floral organs. The transgenic line overexpressing of DcSEP3-1 only showed an early flowering phenotype. All these results indicated that the two DcSEP3s of class E genes in D. chinensis may undergo sub-functionalization. These findings advance our understanding of the molecular mechanisms of flower development in carnation.

  • Introduction

    Surimi gel, known as 'concentrated myofibrillar protein'[1], is a kind of gel prepared by processing fish tissue according to fixed steps, such as rinsing, dehydration, and chopping, then adding a certain number of auxiliary materials for crushing, molding, heating and cooling. Salt-soluble myofibrillar protein (mainly myosin) of surimi denatures and unfolds after heating, and then re-crosslinks and polymerizes to form large protein aggregates[2], which is the internal mechanism of forming the gel structure. To enhance the texture and taste of surimi gel products, 2%−3% salt is added to promote the formation of the protein gel network structure and enhance the solubility and functional properties of the products[3,4]. Nonetheless, numerous studies have confirmed that excessive salt intake may result in risks of disease to human health, such as hypertension, and coronary heart disease[5]. Therefore, the development of low-salt surimi products will be widely focused on in future research.

    Recently, two strategies have been innovatively proposed to improve or maintain the gel properties of low-salt surimi products: one is to use exogenous additives or sodium salt substitutes[6−8], and the other is to exploit new processing technologies[9−11]. Glutamine transaminase (TGase) is the most effective surimi quality improver to enhance the functional properties of protein, which could catalyze acyl donors in proteins (γ-Hydroxylamine group) and acyl receptors (lysine residue, primary amine compound, etc.) undergo acyl transfer reaction to form cross-linked structures[12−14]. Previous studies by Jiang et al.[15] revealed that the cross-linking effect of TGase catalysis depends on the content and spatial distribution of available substrates. In addition, lysine, as an ideal exogenous additive, has been widely used in different meat protein gel systems, which can effectively improve the gel properties of low-salt surimi gel[16] and emulsified chicken sausage[17]. Many researchers have spent a lot of time to obtain higher-quality surimi gel products through the combination of two or more exogenous additives. Many scientists devoted themselves to obtaining higher quality surimi gel products through the combination of two or more exogenous additives. For example, Cao et al.[18] demonstrated that lysine (Lys) could bring about the dissociation of actin under the condition of the presence of TGase, promoting the cooking yield and gel properties of oxidative damaged MP. Similar findings reported by Cando et al.[19] indicated that Lys could induce the changes in protein structure, which were favorable terms to heighten the cross-linking effect of TG and improve the strength of surimi gel.

    Recently, the term ε-Poly-lysine (ε-PL) was followed with interest since it's a natural amino acid polymer produced by microbial fermentation, and was speculated that it has a similar molecular structure and potential effect to Lys[20]. ε-PL, which is generally composed of 25−30 lysine residues connected by amide bonds (by ε-Amino and α-Carboxyl group), was often used as an antibacterial agent for the preservation of meat products and aquatic products[21]. Li et al.[21] explored the effect of preservative coating with ε-PL on the quality of sea bass fillets during storage. It turned out that, ε-PL treatment evidently reduced the thiobarbituric acid and volatile base nitrogen values of bass slices during storage, inhibited the growth of microorganisms, and improved the water retention, texture, and flavor characteristics of the fish. A previous study by Cai et al.[20] proved the bacteriostatic and fresh-keeping effect of the composite coating of protein and sodium alginate on Japanese sea bass, and found that the composite coating had an effect on inhibiting the proliferation of sea bass microorganisms (Escherichia coli, lactic acid bacteria, yeast, etc.), fat oxidation, protein degradation, and nucleotide decomposition. As a natural cationic polypeptide, ε-PL has the advantages of no biological toxicity and low viscosity of aqueous solution. It is noteworthy that it can produce strong electrostatic adsorption with negatively charged amino acids[22]. Its effective modification of protein helps it fully interact with gel component molecules and groups[23], which may play a role in enhancing the texture and water retention of protein gel.

    Nevertheless, few reports are based on the addition of ε-PL to explore the influence mechanism on TGase-catalyzed surimi gel properties. The current study sought to shed light on the effects of different additions of ε-PL on TGase-induced cross-linking effect and the performance of composite surimi gel, to provide a theoretical basis and reference for further research and development of 'low salt', efficient and healthy surimi products.

    Materials and methods

    Materials

    Testing materials, including marine surimi, transglutaminase (TG, enzyme activity 100 IU/g), and ε-Polylysine (ε-PL, ≥ 99% purity) were supplied by Jiangsu Yiming Biological Technology Co., Ltd (Jiangsu, China). Egg white protein was purchased from Henan Wanbang Chemical Technology Co., Ltd (Henan, China). All other chemicals were from Shanghai Yuanye Biochemical Co., Ltd (Shanghai, China) and were at least analytical grade. The ingredients of the surimi gel are shown in Table 1.

    Table 1.  Surimi samples with different treatments.
    GroupsSurimi
    (g)    		TGase
    (w/w, %)    		Egg white
    Protein
    (w/w, %)    		ε-PL
    (w/w, %)    		NaCl
    (w/w, %)
    CK300−−−0.5
    TE3000.47.0−0.5
    TE + P13000.47.00.0050.5
    TE + P23000.47.00.010.5
    TE + P33000.47.00.020.5
    TE + P43000.47.00.040.5
    TE + P53000.47.00.060.5
     | Show Table
    DownLoad: CSV

    Preparation of mixed surimi samples

    The prepared block surimi was firstly put into the chopping machine (or tissue masher) and chopped for 2 min, then different mass fractions of ingredients were added, while the chopping time was extended to 5 min (the temperature should be controlled below 10 °C during this process). The exhausted surimi paste was poured into the special mold (50 mm × 20 mm), which was heated in two stages to form the heat-induced surimi gel (40 °C water bath for 40 min; 90 °C water bath for 20 min). Above prepared surimi gel underwent an ice water bath for 30 min and finally stored overnight at 4 °C for further use.

    Rheological characteristics of mixed surimi samples

    Mixed surimi samples with different treatments were determined under a Haake Mars 60 Rheometer (Thermo Fisher Scientific, Germany) with 35 mm stainless steel parallel plates referring to the method described by Cao et al.[18], and each determination was repeated three times. After centrifugation (1,000× g, 3 min) and 4 °C, the degassed surimi sol (~2 g) was equilibrated at 4 °C for 3 min before measurement.

    Apparent viscosity

    The shear stress of the mixed surimi sol was measured at shear rates between 0−100 s−1.

    Dynamic rheological behavior

    The rheological properties of the mixed surimi sols were measured in an oscillatory mode of CD-Auto Strain at 0.02% and 0.1 Hz frequency, respectively. The heating temperature range is set to 20~90 °C while the heating rate is 1 °C·min−1.

    Strength of mixed surimi gels

    The TA-XT Plus physical property analyzer (TA-XT Plus, Stable Micro Systems Ltd, Surrey, UK) was used to analyze the mixed surimi gel strength of each group of samples (n ≥ 3) at room temperature, and the cube-shaped surimi gel samples are measured through the P/0.5 probe. Referring to the method previously described by Fang et al.[24], the test parameters are as follows, pre-test and test rate (1 mm·s−1); rate after measurement (5 mm·s−1); depressing degree (30%); trigger force (5 g); data acquisition rate (400 p/s).

    Textural properties of mixed surimi gels

    Concerning the method of Jirawat et al.[25], texture profile analysis (TPA) was employed to record the hardness, elasticity, cohesion, chewiness, and resilience of mixed surimi gels. It is well known that TPA can explore the textural properties of food through the texture analyzer (TA-XT Plus, Stable Micro Systems Ltd, Surrey, UK) equipped with a P/75 probe to simulate human oral chewing action and obtain the texture characteristic values related to human sensory evaluation. The physical property parameter settings were as follows: downforce (5 g), compression degree (50%), pre-test speed, test speed, and post-test speed (1.0 mm·s−1).

    Cooking loss of mixed surimi gels

    The cooking loss of surimi gel under different treatments was determined referring to the protocol of Dong et al.[26]. The cooked surimi gel sample was instantly absorbed dry and weighed (W5). The cooking loss (CL) is calculated as follows:

    CL(g/100g)=(M1−M2)/M1×100 (1)

    Where M1, weight of the sample before cooking; M2, weight of the sample after cooking.

    Low-field nuclear magnetic resonance (LF-NMR) of mixed surimi gels

    The LF-NMR of the mixed surimi gel was detected by a PQ001-20-025V NMR analyzer (Niumag Analytical Instruments Co., Ltd, Suzhou, China) referring to the previous method conducted by Li et al.[27]. Relevant characteristic parameters were set as follows: sampling frequency (200 KHZ), echo time (0.3 ms), and cumulative number (8). Keeping the surimi gel sample (approximately 2 g) at room temperature for 30 min, they were carefully put into a cylindrical nuclear magnetic tube (15 mm in diameter), and finally, the relaxation time (T2) was recorded using the Carr Purcell Meiboom Gill (CPMG) pulse sequence.

    Color difference of mixed surimi gels

    CM-5 colorimeter (Konica Minolta Sensing, Inc., Tokyo, Japan) was used for surimi gel with different treatments following to the procedure of Wang et al.[28]. Several 1 cm thick slices were cut from surimi samples (n = 3) selected from different treatment groups, and the gel whiteness was calculated according to the following formula:

    Whiteness=100−√(100−L∗)2+a∗2+b∗2 (2)

    Scanning electron microscopy (SEM) of mixed surimi gels

    According to the previously described procedure by Gao et al.[29], the square-shaped surimi gels (4 mm × 4 mm × 4 mm) were immersed in 0.1 mol·L−1 phosphate buffer (pH 7.2) containing 2.5% (v/v) glutaraldehyde for 24 h. The above samples were washed using phosphate buffer (0.1 mol·L−1, pH 7.2) three times and then subsequently dehydrated in a series of alcohol solutions. The microstructures of the mixed surimi gels were imaged using an FEI Verios 460 SEM (FEI Inc., Hillsboro, OR, USA).

    Thiobarbituric acid-reactive substances (TBARS) determination

    The TBARS value was analyzed by the method described by Hu et al.[30] with slight modification. Thiobarbituric acid solution (1.5 mL) and 8.5 mL of trichloroacetic acid solution were added to the sample in turn, the mixture was bathed in water at 100 °C for 30 min. The supernatant was extracted and centrifuged twice (3,000× g, 5 min): (1) The original supernatant (5 mL) was taken and the same amount of chloroform for mixed centrifugation; (2) The second supernatant (3 mL) and petroleum ether (1.5 mL) were taken for mixed centrifugation. Finally, a small amount of lower liquid was taken to determine the absorbance (A532 nm). The final result was expressed in malondialdehyde equivalent (mg·kg−1).

    Statistical analysis

    All statistical analyses of data were investigated by statistical product and service solutions IBM SPSS Statistics version 23.0 (IBM SPSS Inc., Chicago, USA). The LSD all-pairwise multiple comparison method was used for the least significance analysis, and p < 0.05 was considered to indicate significance. The experimental data are expressed as mean ± standard deviation (SD) and plotted using Origin 2019 (Origin Lab, Northampton, MA, USA) software.

    Results and discussion

    Rheological properties of surimi gels

    Steady-state shear properties

    The steady-state shear flow curve can be used to characterize the interaction between proteins. The steady shear flow changes of apparent viscosity (Pa·s) of composite surimi with shear rate (s−1) under different treatments are shown in Fig. 1a. The apparent viscosity of all samples decreased significantly (p < 0.05) with increasing shear rate, exhibiting shear-thinning behavior[31]. In the range of shear rates from 0.1 to 100 s−1, the samples with TGase addition were always higher than the control, indicating that the induction of TGase enhanced the cross-linking of surimi proteins and formed a more stable structure. The surimi samples added with a lower proportion of ε-PL (0.005% and 0.01%) were regarded as lower viscosity fluid (Fig. 1a). The possible reason was that the low concentration of ε-PL provided a weak effect on the pH value of the surimi system. As a consequence, the content of the net charge provided was relatively small and the electrostatic interaction between the surimi proteins was weakened[20].

    Figure 1.  Effect of different treatments on rheological properties of surimi.
    DownLoad: Full-Size Img PowerPoint
    Dynamic elastic properties during gelation

    The elastic modulus (G′) mainly depends on the interaction between protein molecules, which can reflect the change of elasticity in the heat-induced surimi gel. As shown in Fig. 1b, the gel process of surimi in the control group was a thermodynamic process consisting of two typical stages. In the first stage, the value of G' showed a gradual downward trend in the range of 20~50 °C. This is mainly because, (1) the activity of endogenous protease in surimi is increased; (2) the myosin light chain subunits of surimi are dissociated under the action of protease, forming myosin and actin[24]; (3) heat-induced hydrogen bonds break between protein molecules, thus enhancing the fluidity of the gel system[31]. The second stage: From 50 to 73 °C, the G' value increases rapidly. As the temperature continues to rise to 90 °C, the G 'value keeps rising steadily. At this time, the gel network structure gradually became stable and irreversible.

    Compared with several curves in Fig. 1b, TGase treatment could significantly increase the G' value. The change trend of G' value of the samples added with TGase and ε-PL were similar to that of the control group, but the former increased faster and the maximum value of G' was also significantly higher. The temperature corresponding to the first peak of G' gradually decreased (PL1≈PL2 < PL4≈TE < PL3≈PL5 < CK), indicating that the process of protein denaturation and aggregation was advanced. This result showed that the proper amount of ε-PL (0.04%) in combination with TGase can reduce the thermal denaturation temperature of protein-forming gel and improve the forming ability of composite gel, which was unanimous with the changes in texture and properties of surimi gel (Table 2). Furthermore, the addition of a small amount (0.005%) or an excessive amount (0.06%) of ε-PL made the mixed surimi protein system more unstable, affecting the ability of TG-induced gel formation as the last resort[32].

    Table 2.  Effect of different treatments on the textural properties of surimi gels.
    GroupsHardness (g)SpringinessCohesivenessChewiness (g)Resilience
    CK811.40 ± 45.28de0.81 ± 0.01a0.53 ± 0.02b498.36 ± 21.58c0.21 ± 0.01e
    TE1105.80 ± 61.83c0.83 ± 0.01a0.56 ± 0.01b510.40 ± 26.04c0.24 ± 0.00bcd
    TE + P1736.01 ± 18.49e0.80 ± 0.03a0.61 ± 0.00a348.78 ± 18.36d0.23 ± 0.01cde
    TE + P2777.45 ± 39.61de0.80 ± 0.01a0.60 ± 0.02a307.03 ± 12.97e0.22 ± 0.00de
    TE + P3869.66 ± 45.82d0.83 ± 0.02a0.63 ± 0.01a485.06 ± 22.73c0.28 ± 0.00a
    TE + P41492.80 ± 77.13a0.83 ± 0.01a0.60 ± 0.01a721.74 ± 31.55a0.26 ± 0.01ab
    TE + P51314.60 ± 84.10b0.81 ± 0.00a0.60 ± 0.02a652.36 ± 30.24b0.25 ± 0.01bc
    Different lowercase letters in the same column indicated significant differences (p < 0.05).
     | Show Table
    DownLoad: CSV

    Strength of surimi gels

    Gel strength is one of the vital indicators to test the quality of surimi products, which directly affects the texture characteristics and sensory acceptance of the products. The strength of mixed surimi gel with TGase was significantly enhanced by 23.97% (p < 0.05) compared with the control group after heat-inducing. This enhancement is probably caused by the crosslinking promotion of TGase (Fig. 2a). A deeper explanation is that under the catalysis of TGase, the ε-amino group on lysine and the γ-amide group on glutamic acid residues undergo acylation reaction inside or between proteins, forming ε-(γ-Glutamyl)-lysine covalent cross-linking bond which promotes the production of the protein gel network[26].

    Figure 2.  (a) Catalytic reaction of glutamine transaminase and (b) effect of different treatments on gel strength and cooking loss of surimi gel. a−d/A−D: values with different lowercase letters indicate significant difference (p < 0.05).
    DownLoad: Full-Size Img PowerPoint

    On the basis of adding TGase, the strength of the mixed gel with ε-PL concentration ranging from 0.005% to 0.03% was lower than that of TE (Fig. 2b). It was speculated that the surimi sample with low concentration ε-PL was a fluid with lower viscosity, and the interaction between protein and water is strengthened, while the electrostatic interaction between proteins is further weakened[33]. This was also consistent with the change in rheological properties in Fig. 1a. Nevertheless, with the increase of ε-PL content to 0.04%, the gel strength of surimi gel significantly increased and reached the highest value (781.63 g·cm), which was about 21.03% higher than that of the TE group (p < 0.05) (Fig. 2b). The increase of gel strength in this process was obtained due to the following three possible reasons, (1) ε-PL is a cationic amino acid with positive charge, which can improve the pH value of protein or meat product system; (2) The interaction between the ε-amino group of ε-PL and the aromatic residue of protein, namely the cation-π interaction, can change the structure of meat protein[34]; (3) Protein (mixed surimi system) with high ε-amino group content, TGase has strong gel improving ability[35].

    Such synergy (ε-PL = 0.04%), as a comprehensive result of different impactors, is that after the surimi was mixed under the optimal ratio conditions, the synthesis of TGase enzyme catalysis, pH value shift, changes in protein and amino acid composition, etc., increased the strength of various forces, thus forming a denser stereoscopic network structure. Note that when the content of ε-PL reached 0.06%, the gel strength of the corresponding surimi gel decreased by 10% compared with 0.04%. Similarly, others reported the result that alkaline amino acids led to the reduction of the strength of the myosin gel of bighead carp[36].

    Textural properties of surimi gels

    TPA, also known as whole texture, is a comprehensive parameter that determines the sensory quality of surimi gel, including hardness, elasticity, cohesion, chewiness, and resilience[37]. As shown in Table 2, the addition of TGase significantly improved the texture properties of surimi gel (p < 0.05), which is related to TGase's ability to induce surimi protein to form more ε-(γ-Glu)-Lys covalent bond during heating[38] (Fig. 2a). Compared with the cross-linking induced by TGase alone, the gel hardness of the mixed surimi gel treated with ε-PL showed a similar change to the gel strength (Fig. 2b). As the concentration of ε-PL increased from 0.005% to 0.04%, the hardness of surimi gel gradually increased until it reached the maximum (1,492.80 g). At the same time, we also observed that the elasticity, cohesion, and chewiness of the composite gel reached the highest values with the 0.04% ε-PL, and these were higher than those of the TGase-only group. Similar to the findings of Ali et al.[39], the author found that the combination of ε-PL and beetroot extract can effectively replace nitrite, which produced a marked effect in maintaining the color of Frankfurt sausage and improving the texture and performance. However, the data we collated above (Table 2) also showed a clear phenomenon, that is, the addition of ε-PL with lower concentration (0.005%−0.02%) or highest concentration (0.06%) was not conducive to the combination with TGase to improve the texture characteristics of mixed surimi gel.

    Cooking loss of mixed surimi gels

    Cooking loss indicates the water holding capacity of heated surimi, which usually represents the stability of the three-dimensional network structure of surimi gel[40]. The 0.4% TGase significantly reduced the cooking loss of surimi samples (p < 0.05), which was 4.91% lower than that of the control group (Fig. 2b). When the addition of PL (combined with TGase) gradually increased from 0.005% to 0.04%, the cooking loss of surimi showed a decreasing trend and reached the minimum at 0.04%. The ε-PL-added surimi gel samples had higher cooking loss compared with that of only with TGase. Most notably, this may be due to ε-PL is able to further exert the cross-linking effect of TGase. A similar finding was reported in the study by Ma et al.[22], adding ε-PL is able to improve the solubility of myofibrillar proteins. Proteins with high solubility are more easily induced by TGase during heating, which aggravates the cross-linking between ε-PL-protein or protein-protein and forms a disordered gel network structure with relatively weaker water-holding capacity.

    Color of surimi gels

    As shown in Table 3, the high lightness (L*), low yellowness (b*), and high whiteness of surimi in the control group were relatively low, with values of 72.49, 10.42, and 70.56 respectively. After TGase was added to induce cross-linking, these values increased significantly (p < 0.05), which may be related to the photochromic effect of water molecules released from gel matrix under TGase-induced surimi protein cross-linking reported in the previous study[41]. Furthermore, on the basis of adding TGase, it was interesting to see that the L* and whiteness values of surimi gel first increased and then gradually decreased with the increase in ε-PL concentration. The influence of ε-PL combined with TGase on the whiteness of gel can be attributed to three reasons: (1) The addition of ε-PL can effectively increase the substrate content of TGase, and promote the cross-linking between proteins, so as to obtain a much more compact surimi gel structure, which affects the refractive index of light; (2) The water retention performance of the high surimi gel was significantly improved with the addition of ε-PL[42] (Fig. 2b), at this time, the L* value (positively related to the whiteness) value showed a decreasing trend with the decrease of the surface free water content of the gel sample; (3) With the increase of ε-PL concentration, some colored substances, formed due to the accelerated Maillard reaction rate during the preparation of gel, may have an adverse effect on the improvement of gel whiteness[43]. After adding TGase to induce cross-linking, although the whiteness value of composite surimi was significantly enhanced, ε-PL was not enough to further improve the whiteness value of final mixed surimi gel, and high concentration so far as to have a negative impact on the whiteness value.

    Table 3.  Effect of different treatments on the color of surimi gels.
    GroupsL*a*b*Whiteness
    CK72.49 ± 0.82e−0.92 ± 0.01e10.42 ± 0.33d70.56 ± 0.65d
    TE77.82 ± 0.34ab−0.23 ± 0.02c12.29 ± 0.29bc74.64 ± 0.26ab
    TE + P178.39 ± 0.40a−0.14 ± 0.01a12.46 ± 0.12ab75.05 ± 0.41a
    TE + P278.42 ± 0.43a−0.17 ± 0.0b12.46 ± 0.15ab75.07 ± 0.32a
    TE + P377.48 ± 0.16b−0.18 ± 0.02b12.37 ± 0.09abc74.31 ± 0.11b
    TE + P476.34 ± 0.05c−0.22 ± 0.01c12.73 ± 0.02a73.13 ± 0.04c
    TE + P575.48 ± 0.18d−0.26 ± 0.01d12.01 ± 0.14c72.70 ± 0.19c
    Different lowercase letters in the same column indicated significant differences (p < 0.05).
     | Show Table
    DownLoad: CSV

    Changes in moisture distribution of surimi gels

    The water distribution in surimi gel products was measured by LF-NMR[44], and the results were inverted to obtain the transverse relaxation time (T2), which reflects the strength of water fluidity[45]. There are four fitted wave peaks which are assigned to four different water distribution states and wave peak ranges (Fig. 3, Table 4): strong bound water T21 (0.1−1 ms), weak bound water T22 (1−10 ms), non-flowing water T23 (10−100 ms) and free water T24 (100−1,000 ms)[46]. At the same time, similar characteristics (the main peak is centered on T23) are possessed by the water distribution of all surimi gel samples. The addition of TGase increased the proportion of non-flowing water, accompanying the significant decrease in the content of free water (p < 0.05), compared with the control group. It proved that the addition of TGase brought this phenomenon, namely the bound water in surimi gel was partially transferred to the non-flowing, which also indicated the reduction of cooking loss of surimi samples induced by TGase (Fig. 2). On the basis of adding TGase, the low level of ε-PL (0.005%, 0.01% and 0.02%) inhibited the transition of free water in surimi gel to non-flowing water, in which the proportion of T23 decreased by 2.05%, 2.74%, and 1.42% respectively compared with the surimi gel only with TGase, while T24 increased by 15.76%, 14.17%, and 4.43% respectively. The proportion of P23 in the surimi gel sample (ε-PL = 0.04%) was equivalent to that of the TE group, implying that the addition of appropriate ε-PL was not directly connected with the changes in water distribution in surimi after TGase-induced cross-linking, and slight addition would have a negative impact, which was unanimous with the above research results of cooking loss (Fig. 2a).

    Figure 3.  Effect of different treatments on the transverse relaxation time T2 of surimi gel.
    DownLoad: Full-Size Img PowerPoint
    Table 4.  Effect of different treatments on the transverse relaxation time T2 of surimi gel.
    GroupsP21 (%)P22 (%)P23 (%)P24 (%)
    CK2.175 ± 0.186c1.198 ± 0.012e82.863 ± 0.691bc13.764 ± 0.091a
    TE1.938 ± 0.095d2.166 ± 0.043a85.144 ± 1.336a10.752 ± 0.033e
    TE + P12.705 ± 0.067b1.414 ± 0.009d83.435 ± 1.616b12.446 ± 0.105c
    TE + P23.005 ± 0.003a1.845 ± 0.056b82.874 ± 1.739bc12.276 ± 0.108c
    TE + P33.107 ± 0.063a1.715 ± 0.033c83.950 ± 1.587ab11.228 ± 0.086d
    TE + P41.770 ± 0.018d2.099 ± 0.059a85.021 ± 1.756a11.110 ± 0.144d
    TE + P53.121 ± 0.007a1.758 ± 0.107bc82.136 ± 1.091c12.985 ± 0.018b
    Different lowercase letters in the same column indicated significant differences (p < 0.05).
     | Show Table
    DownLoad: CSV

    Scanning electron microscopy of surimi gels

    The effect of different treatment methods on the microstructure of surimi gel was observed by SEM. As shown in Fig. 4, the microstructure of the control surimi gel (Fig. 4a) was observed to be enormously loose, uneven, and irregular, with large pores, which explained the reason why the control surimi gel had low strength and large cooking loss (Fig. 2b). In addition, the morphological properties of another group of surimi gel (TGase-induced) are appreciably different from the scanning electron micrograph mentioned above (Fig. 4b). Numerous compact and evenly distributed small pores were observed, instead of the loose structure in the control sample, which accounted for the fact that TGase could interact with proteins to form a more uniform and orderly three-dimensional network structure in the process of gel formation[47]. Moreover, similar findings were also reported in the previous studies of Dong et al.[26]. When treated with TGase and ε-PL (from 0.05% to 0.04%), the surface of the surimi gel sample gradually became flat through observation (Fig. 4f). We found that some smaller pores were formed and some larger pores were slightly supplemented visually. Remarkably, when the addition of ε-PL increased to 0.06% (Fig. 4g), the structure of surimi gel was not as uniform as before, and some large and irregular holes appeared obviously. This phenomenon might be related to moderate ε-PL, especially 0.02%, which can promote the cross-linking of TGase with protein and the aggregation/denaturation of different components, which agreed with the change of coagulation strength of surimi samples.

    Figure 4.  Effect of different treatments on the microstructure of surimi.
    DownLoad: Full-Size Img PowerPoint

    Thiobarbituric acid-reactive substances (TBARS) determination

    TBARS value, which can reflect the degree of lipid oxidation and rancidity of surimi, is an important indicator for the occurrence of oxidation[48]. Some substances in surimi, such as unsaturated fatty acids, will inevitably undergo oxidative decomposition to produce a large amount of malondialdehyde (MDA), the latter reacts easily with thiobarbituric acid (TBA) reagent to produce red compounds with maximum absorbance at 532 nm. As illustrated in Fig. 5, when TGase and a certain amount of PL (from 0.005% to 0.06%) were added, the TBARs value of surimi gels decreased to 2.03 and 1.67 mg/kg respectively, compared with the control group (2.26 mg/kg). This shows that the addition of both can significantly reduce the TBARS value of surimi gel (p < 0.05), considered to be a cue for the fat oxidation of surimi being inhibited. In addition, we also found that the antioxidant effect of PL was dose-dependent. The ε-PL can be chelated by ferrous ions along with the ability to scavenge free radicals like hydroxyl radicals, ensuring its antioxidant properties[33]. The ε-PL was prospectively considered as an antioxidant additive to prevent surimi protein from deteriorating induced by oxidation[49]. Similarly, making use of lysine or ε-PL as antioxidants in plant protein and meat protein has been widely reported[33, 50]. Fan et al.[42] confirmed that ε-PL addition has a significant effect on maintaining a high total phenolic content and vitamin C levels in fresh lettuce, which also shows that it has certain antioxidant activity.

    Figure 5.  Effect of different treatments on TBARS values of surimi gel. a−f: values with different lowercase letters indicate significant difference (p < 0.05).
    DownLoad: Full-Size Img PowerPoint

    Conclusions

    The addition of ε-PL at different concentrations had an apparent impact on the characteristics of TGase-induced mixed surimi gel, accompanied by the following situations: The 0.04% ε-PL provided a synergistic effect to promote the aggregation and crosslinking of surimi proteins induced by TGase; The rheology, LF-NMR and SEM results showed that the appropriate concentration (0.04%) of ε-PL apparently enhanced the initial apparent viscosity and elasticity of surimi samples, which was conducive to the formation of a more dense and uniform three-dimensional network structure, further limiting the flow of water in surimi and the exudation of hydrophilic substances; Simultaneously, the network strength was strengthened along with the texture properties of the mixed surimi gel. Furthermore, ε-PL had a strong ability to inhibit lipid oxidation in mixed surimi gel, showing a concentration dependence. When the content of ε-PL ran to lowest (0.005%−0.01%) or highest (0.6%), the improvement of the quality of surimi mixed gel was opposite to the above. The results show that ε-PL can be perceived as a prospective polyfunctional food additive to improve the texture properties, nutritional advantages, and product stability of surimi products.

  • The authors confirm contribution to the paper as follows: study conception and design: Cao Y, Xiong YL, Yuan F, Liang G; data collection: Liang G, Cao Y, Li Z, Liu M; analysis and interpretation of results: Li Z, Cao Y, Liang G, Liu Z, Liu M; draft manuscript preparation: Li Z, Cao Y, Liu ZL. All authors reviewed the results and approved the final version of the manuscript.

  • The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

    • Acknowledgments

    This work was financially supported by the Natural Science Basic Research Program of Shaanxi (No. 2023-JC-YB-146), the fund of Cultivation Project of Double First-Class Disciplines of Food Science and Engineering, Beijing Technology & Business University (No. BTBUKF202215), the Innovation Capability Support Plan of Shaanxi (No. 2023WGZJ-YB-27), the Agricultural Technology Research and Development Project of Xi'an Science and Technology Bureau (No. 22NYYF057), and Jiangsu Yiming Biological Technology Co., Ltd. in China.

  • The authors declare that they have no conflict of interest.

  • Supplemental Table S1 Primers for CDS amplification of class E genes.
    Supplemental Table S2 The CDS of class E genes.
    Supplemental Table S3 Protein sequences for phylogenetic tree.
    Supplemental Table S4 Primers for qRT-PCR.
    Supplemental Table S5 Primers for Yeast two‐hybrid of class E genes.
    Supplemental Table S6 Primers for BiFC of class E genes.
    Supplemental Table S7 Transcriptome sequencing data statistics.
    Supplemental Table S8 Distribution of gene expression in transcriptome samples at differentdevelopmental stages.
    Supplemental Table S9 Summery of class E genes in D. chinensis and D. caryophyllus.
    Supplemental Fig. S1 Alignment of D. chinensis (Dc) class E amino acid sequences with A. thaliana (At) and B. vulgaris (Bv).
    Supplemental Fig. S2 The phylogenetic tree of the class E genes.
    Supplemental Fig. S3 Yeast interaction analysis of E proteins of D. chinensis.
    Supplemental Fig. S4 Protein self-activation assay of class E genes.
    Supplemental Fig. S5 BIFC analysis of E proteins of D. chinensis.
    Supplemental Fig. S6 Rosettes number analysis of transgenic lines overexpressing DcSEP3-2.
    Supplemental Fig. S7 Phenotype analysis of transgenic lines of 35S:DcSEP3-1 and 35S:DcSEP3-2.
  • [1]

    Coen ES, Meyerowitz EM. 1991. The war of the whorls: genetic interactions controlling flower development. Nature 353:31−37

    doi: 10.1038/353031a0

    CrossRef   Google Scholar

    [2]

    Pelaz S, Ditta GS, Baumann E, Wisman E, Yanofsky MF. 2000. B and C floral organ identity functions require SEPALLATA MADS-box genes. Nature 405:200−3

    doi: 10.1038/35012103

    CrossRef   Google Scholar

    [3]

    Ma H, Yanofsky MF, Meyerowitz EM. 1991. AGL1-AGL6, an Arabidopsis gene family with similarity to floral homeotic and transcription factor genes. Genes & Development 5:484−95

    doi: 10.1101/gad.5.3.484

    CrossRef   Google Scholar

    [4]

    Huang H, Tudor M, Weiss CA, Hu Y, Ma H. 1995. The Arabidopsis MADS-box gene AGL3 is widely expressed and encodes a sequence-specific DNA-binding protein. Plant Molecular Biology 28:549−67

    doi: 10.1007/BF00020401

    CrossRef   Google Scholar

    [5]

    Mandel MA, Yanofsky MF. 1998. The Arabidopsis AGL9 MADS box gene is expressed in young flower primordia. Sexual Plant Reproduction 11:22−28

    doi: 10.1007/s004970050116

    CrossRef   Google Scholar

    [6]

    Zahn LM, Kong H, Leebens-Mack JH, Kim S, Soltis PS, et al. 2005. The evolution of the SEPALLATA subfamily of MADS-box genes: a preangiosperm origin with multiple duplications throughout angiosperm history. Genetics 169:2209−23

    doi: 10.1534/genetics.104.037770

    CrossRef   Google Scholar

    [7]

    Ditta G, Pinyopich A, Robles P, Pelaz S, Yanofsky MF. 2004. The SEP4 gene of Arabidopsis thaliana functions in floral organ and meristem identity. Current Biology 14:1935−40

    doi: 10.1016/j.cub.2004.10.028

    CrossRef   Google Scholar

    [8]

    Pelaz S, Tapia-López R, Alvarez-Buylla ER, Yanofsky MF. 2001. Conversion of leaves into petals in Arabidopsis. Current Biology 11:182−84

    doi: 10.1016/S0960-9822(01)00024-0

    CrossRef   Google Scholar

    [9]

    Honma T, Goto K. 2001. Complexes of MADS-box proteins are sufficient to convert leaves into floral organs. Nature 409:525−29

    doi: 10.1038/35054083

    CrossRef   Google Scholar

    [10]

    Theißen G, Saedler H. 2001. Floral quartets. Nature 409:469−71

    doi: 10.1038/35054172

    CrossRef   Google Scholar

    [11]

    Theißen G, Melzer R, Rümpler F. 2016. MADS-domain transcription factors and the floral quartet model of flower development: linking plant development and evolution. Development 143:3259−71

    doi: 10.1242/dev.134080

    CrossRef   Google Scholar

    [12]

    Immink RGH, Tonaco IAN, de Folter S, Shchennikova A, van Dijk ADJ, et al. 2009. SEPALLATA3: the 'glue' for MADS box transcription factor complex formation. Genome Biology 10:R24

    doi: 10.1186/gb-2009-10-2-r24

    CrossRef   Google Scholar

    [13]

    Wang P, Wang S, Chen Y, Xu X, Guang X, Zhang Y. 2019. Genome-wide Analysis of the MADS-Box Gene Family in Watermelon. Computational Biology and Chemistry 80:341−50

    doi: 10.1016/j.compbiolchem.2019.04.013

    CrossRef   Google Scholar

    [14]

    Xu Z, Zhang Q, Sun L, Du D, Cheng T, et al. 2014. Genome-wide identification, characterisation and expression analysis of the MADS-box gene family in Prunus mume. Molecular Genetics and Genomics 289:903−20

    doi: 10.1007/s00438-014-0863-z

    CrossRef   Google Scholar

    [15]

    Arora R, Agarwal P, Ray S, Singh AK, Singh VP, et al. 2007. MADS-box gene family in rice: genome-wide identification, organization and expression profiling during reproductive development and stress. BMC Genomics 8:242

    doi: 10.1186/1471-2164-8-242

    CrossRef   Google Scholar

    [16]

    Saha G, Park JI, Jung HJ, Ahmed NU, Kayum MA, et al. 2015. Genome-wide identification and characterization of MADS-box family genes related to organ development and stress resistance in Brassica rapa. BMC Genomics 16:178

    doi: 10.1186/s12864-015-1349-z

    CrossRef   Google Scholar

    [17]

    Ampomah-Dwamena C, Morris BA, Sutherland P, Veit B, Yao JL. 2002. Down-regulation of TM29, a tomato SEPALLATA homolog, causes parthenocarpic fruit development and floral reversion. Plant Physiology 130:605−17

    doi: 10.1104/pp.005223

    CrossRef   Google Scholar

    [18]

    Kotilainen M, Elomaa P, Uimari A, Albert VA, Yu D, et al. 2000. GRCD1, an AGL2-like MADS box gene, participates in the C function during stamen development in Gerbera hybrida. The Plant Cell 12:1893−902

    doi: 10.1105/tpc.12.10.1893

    CrossRef   Google Scholar

    [19]

    Malcomber ST, Kellogg EA. 2005. SEPALLATA gene diversification: brave new whorls. Trends in Plant Science 10:427−35

    doi: 10.1016/j.tplants.2005.07.008

    CrossRef   Google Scholar

    [20]

    Pan Z, Chen Y, Du JS, Chen Y, Chung MC, et al. 2014. Flower development of Phalaenopsis orchid involves functionally divergent SEPALLATA-like genes. New Phytologist 202:1024−42

    doi: 10.1111/nph.12723

    CrossRef   Google Scholar

    [21]

    Soza VL, Snelson CD, Hewett Hazelton KD, Di Stilio VS. 2016. Partial redundancy and functional specialization of E-class SEPALLATA genes in an early-diverging eudicot. Developmental Biology 419:143−55

    doi: 10.1016/j.ydbio.2016.07.021

    CrossRef   Google Scholar

    [22]

    Vrebalov J, Ruezinsky D, Padmanabhan V, White R, Medrano D, et al. 2002. A MADS-box gene necessary for fruit ripening at the tomato Ripening-Inhibitor (Rin) locus. Science 296:343−6

    doi: 10.1126/science.1068181

    CrossRef   Google Scholar

    [23]

    Zhou Y, Xu Z, Yong X, Ahmad S, Yang W, et al. 2017. SEP-class genes in Prunus mume and their likely role in floral organ development. BMC Plant Biology 17:10

    doi: 10.1186/s12870-016-0954-6

    CrossRef   Google Scholar

    [24]

    Pi M, Hu S, Cheng L, Zhong R, Cai Z, et al. 2021. The MADS-box gene FveSEP3 plays essential roles in flower organogenesis and fruit development in woodland strawberry. Horticulture Research 8:247

    doi: 10.1038/s41438-021-00673-1

    CrossRef   Google Scholar

    [25]

    Wang Y, Li J. 2008. Molecular basis of plant architecture. Annual Review of Plant Biology 59:253−79

    doi: 10.1146/annurev.arplant.59.032607.092902

    CrossRef   Google Scholar

    [26]

    Zhang X, Lin S, Peng D, Wu Q, Liao X, et al. 2022. Integrated multi-omic data and analyses reveal the pathways underlying key ornamental traits in carnation flowers. Plant Biotechnology Journal 20:1182−96

    doi: 10.1111/pbi.13801

    CrossRef   Google Scholar

    [27]

    Kim D, Langmead B, Salzberg SL. 2015. HISAT: a fast spliced aligner with low memory requirements. Nature Methods 12:357−60

    doi: 10.1038/nmeth.3317

    CrossRef   Google Scholar

    [28]

    Wang Q, Zhang X, Lin S, Yang S, Yan X, et al. 2020. Mapping a double flower phenotype-associated gene DcAP2L in Dianthus chinensis. Journal of Experimental Botany 71:1915−27

    doi: 10.1093/jxb/erz558

    CrossRef   Google Scholar

    [29]

    Yagi M, Kosugi S, Hirakawa H, Ohmiya A, Tanase K, et al. 2014. Sequence analysis of the genome of carnation (Dianthus caryophyllus L.). DNA Research 21:231−41

    doi: 10.1093/dnares/dst053

    CrossRef   Google Scholar

    [30]

    Zhang X, Wang Q, Yang S, Lin S, Bao M, et al. 2018. Identification and Characterization of the MADS-Box Genes and Their Contribution to Flower Organ in Carnation (Dianthus caryophyllus L.). Genes 9:193

    doi: 10.3390/genes9040193

    CrossRef   Google Scholar

    [31]

    Tamura K, Stecher G, Peterson D, Filipski A, Kumar S. 2013. MEGA6: Molecular Evolutionary Genetics Analysis version 6.0. Molecular Biology and Evolution 30:2725−9

    doi: 10.1093/molbev/mst197

    CrossRef   Google Scholar

    [32]

    Livak KJ, Schmittgen TD. 2001. Analysis of relative gene expression data using real-time quantitative PCR and the 2−ΔΔCᴛ Method. Methods 25:402−8

    doi: 10.1006/meth.2001.1262

    CrossRef   Google Scholar

    [33]

    Walter M, Chaban C, Schütze K, Batistic O, Weckermann K, et al. 2004. Visualization of protein interactions in living plant cells using bimolecular fluorescence complementation. The Plant Journal 40:428−38

    doi: 10.1111/j.1365-313X.2004.02219.x

    CrossRef   Google Scholar

    [34]

    Clough SJ, Bent AF. 1998. Floral dip: a simplified method for Agrobacterium-mediated transformation of Arabidopsis thaliana. The Plant Journal 16:735−43

    doi: 10.1046/j.1365-313x.1998.00343.x

    CrossRef   Google Scholar

    [35]

    Schilling S, Kennedy A, Pan S, Jermiin LS, Melzer R. 2020. Genome-wide analysis of MIKC-type MADS-box genes in wheat: pervasive duplications, functional conservation and putative neofunctionalization. New Phytologist 225:511−29

    doi: 10.1111/nph.16122

    CrossRef   Google Scholar

    [36]

    Kaufmann K, Muiño JM, Jauregui R, Airoldi CA, Smaczniak C, et al. 2009. Target genes of the MADS transcription factor SEPALLATA3: integration of developmental and hormonal pathways in the Arabidopsis flower. PLoS Biology 7:e1000090

    doi: 10.1371/journal.pbio.1000090

    CrossRef   Google Scholar

    [37]

    Ruokolainen S, Ng YP, Albert VA, Elomaa P, Teeri TH. 2010. Large scale interaction analysis predicts that the Gerbera hybrida floral E function is provided both by general and specialized proteins. BMC Plant Biology 10:129

    doi: 10.1186/1471-2229-10-129

    CrossRef   Google Scholar

    [38]

    Matsunaga S, Uchida W, Kejnovsky E, Isono E, Moneger F, et al. 2004. Characterization of two SEPALLATA MADS-box genes from the dioecious plant Silene latifolia. Sexual Plant Reproduction 17:189−93

    doi: 10.1007/s00497-004-0230-z

    CrossRef   Google Scholar

    [39]

    Zhang S, Lu S, Yi S, Han H, Liu L, et al. 2017. Functional conservation and divergence of five SEPALLATA-like genes from a basal eudicot tree, Platanus acerifolia. Planta 245:439−57

    doi: 10.1007/s00425-016-2617-0

    CrossRef   Google Scholar

    [40]

    Zhang C, Wei L, Yu X, Li H, Wang W, et al. 2021. Functional conservation and divergence of SEPALLATA-like genes in the development of two-type florets in marigold. Plant Science 309:110938

    doi: 10.1016/j.plantsci.2021.110938

    CrossRef   Google Scholar

    [41]

    Dreni L, Ferrándiz C. 2022. Tracing the evolution of the SEPALLATA subfamily across angiosperms associated with neo- and sub-functionalization for reproductive and agronomically relevant traits. Plants 11:2934

    doi: 10.3390/plants11212934

    CrossRef   Google Scholar

    [42]

    Gramzow L, Weilandt L, Theißen G. 2014. MADS goes genomic in conifers: towards determining the ancestral set of MADS-box genes in seed plants. Annals of Botany 114:1407−29

    doi: 10.1093/aob/mcu066

    CrossRef   Google Scholar

    [43]

    Kafri R, Dahan O, Levy J, Pilpel Y. 2008. Preferential protection of protein interaction network hubs in yeast: evolved functionality of genetic redundancy. PNAS 105:1243−48

    doi: 10.1073/pnas.0711043105

    CrossRef   Google Scholar

    [44]

    de Folter S, Immink RGH, Kieffer M, Pařenicová L, Henz SR, et al. 2005. Comprehensive interaction map of the Arabidopsis MADS Box transcription factors. The Plant Cell 17:1424−33

    doi: 10.1105/tpc.105.031831

    CrossRef   Google Scholar

  • Cite this article

    Zhang X, Wu Q, Lin S, Li D, Bao M, et al. 2023. Identification and characterization of class E genes involved in floral organ development in Dianthus chinensis. Ornamental Plant Research 3:5 doi: 10.48130/OPR-2023-0005
    Zhang X, Wu Q, Lin S, Li D, Bao M, et al. 2023. Identification and characterization of class E genes involved in floral organ development in Dianthus chinensis. Ornamental Plant Research 3:5 doi: 10.48130/OPR-2023-0005
    shu

Figures(6)  /  Tables(1)

Download PDF

Article Metrics

Article views(5199) PDF downloads(696)

Other Articles By Authors

ARTICLE   Open Access    

Identification and characterization of class E genes involved in floral organ development in Dianthus chinensis

  • 1.

    National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, China

  • 2.

    Guangdong Laboratory for Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, Guangdong, China

  • Received: 11 January 2023
  • Accepted: 09 February 2023
  • Published online: 15 March 2023
Ornamental Plant Research  3,  Article number: 5  (2023)  |  Cite this article

Abstract: The SEPALLATA (SEP) gene, as a 'glue' for the 'floral quartets model', plays an important role in floral organ development by forming tetramers with class A-, B-, and C- genes. The functional differentiation of class E genes has been reported in different species. Carnation (Dianthus spp.) is a world-famous economic flower that has been extensively used in landscaping, but the roles of SEP genes in carnation are unclear. Here, we found that the class E genes of D. chinensis cultivar 'L' showed different expression patterns during floral organ primordium development by transcriptome analysis. Combined with quantitative real-time PCR, its tissue and specific stage expression patterns were also different in different subclades. In addition, a yeast two-hybrid experiment was carried out to explore the interaction patterns of class E genes with other class A-, B-, and C- genes. Only DcSEP3s and DcSEP4s proteins interacted with all three classes of A-, B-, and C- proteins, and interestingly, is that DcSEP3-1 only interacted with the DcAP1 protein of class A, while the DcSEP3-2 protein only interacted with DcFUL1. Transgenic experiments showed that overexpression of DcSEP3-2 genes in Arabidopsis resulted in early flowering, smaller rosettes, dwarfism and abnormal floral organs. The transgenic line overexpressing of DcSEP3-1 only showed an early flowering phenotype. All these results indicated that the two DcSEP3s of class E genes in D. chinensis may undergo sub-functionalization. These findings advance our understanding of the molecular mechanisms of flower development in carnation.

    HTML

    INTRODUCTION

    • Carnation (Dianthus spp.) is popular ornamental flower; D. caryouphyllus and D. chinensis are widely planted and enjoyed by people worldwide. Flowers, as important ornamental plants, are widely studied. Varied flower shapes or florescence affect the economic value of ornamental plants. Thus, understanding the molecular mechanism of floral organ development and functional differentiation of these regulatory genes in carnation will aid in accelerating breeding improvement.

      As early as 1991, the 'ABC model' of flower development was proposed in Arabidopsis thaliana and Antirrhinum majus[1]. In this model, class A, class B and class C genes were thought to regulate floral organ formation. Subsequently, the class E genes involved in the formation of floral organs were later discovered[2]. In Arabidopsis, four SEP genes were identified[3−5]: AtSEP1, AtSEP2, AtSEP3 and AtSEP4, all of which were expressed in the primordia of four whorl floral organs[6]. None of these four genes had any phenotype if they were individually mutated. However, in sep1/sep2/sep3 mutants, the petals, stamens and carpels of plants all changed into calyx sheet structures[2]. In the sep1/sep2/sep3/sep4 mutants, the normal floral primordium was absent, and all four floral organs became leaf like structures, suggesting that SEP genes were indispensable in controlling floral primordium formation[7−9].

      Subsequently, the classical 'ABC model' of flower development was further improved with the discovery of the function of class E genes. The 'Floral quartets model'[10] was proposed, which showed that class A-, B-, C- and E- proteins interacted to regulate plant flowering and were continuously developing: AP1–AP1–SEP–SEP protein interactions were involved in sepal development, AP1–AP3–PI–SEP interactions determined petal development, AG–AP3–PI–SEP interactions determined stamen development, AG–AG–SEP–SEP interactions determined carpel development and AG–SHP–STK–SEP interactions determined ovule development[11]. In this model, every whorl of floral organ formation was regulated by at least one SEP protein, so class E genes were referred to as the 'glue' in the 'quartet model'[11,12].

      In recent years, the function of class E genes has been reported in an increasing number of species. Previous studies have shown that the number of class E genes identified varies among different species; for example, two class E genes were identified in watermelon[13], four in Prunus mume[14], five in Oryza sativa[15] and ten in Brassica rapa[16]. These genes belonged to different subclades of class E genes, such as the SEP1/2, FBP9/23 and SEP4 subclades, which were derived from LOFSEP, which produced two consecutive gene copies in dicotyledons[6].

      Previous studies have also found that the functions of SEP genes in many plants[17−23] are diverse, which may be involved in determining floral organ identity and plant architecture, fruit maturation and the transition from vegetative growth to reproductive growth processes. For example, in Phalaenopsis orchid, silenced PeSEP3 made the tepal a leaf-like organ. Downregulation of TM29 caused tomato parthenocarpic fruit development and floral reversion. However, in strawberry, FveSEP3 inhibited fruit growth in the absence of pollination and promoted fruit ripening[24]. These reports suggested that class E genes experienced functional redundancy and new functionalization in the process of evolution. However, to date, the roles of class E genes in flower development or whether they experience sub-functionalization and neo-functionalization in carnation remain unclear.

      In this study, through transcriptome comparative analysis, we found that the expression of class E genes increased gradually in the first three stages (Sepal (S2), petal (S3), and stamen (S4) primordium development) after flowering initiation (S1). To explore the roles of class E genes in the development of flowers in carnation, six SEP-like genes were identified in D. chinensis. Then the expression patterns of these class E genes were analyzed by quantitative real-time PCR (qRT‒PCR). The interactions of class E proteins of D. chinensis were also investigated by yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays. In addition, the functions of SEP3 genes with different expression and interaction patterns were analyzed. This study demonstrated the role of class E genes in flower development, which lays a theoretical foundation for understanding the mechanism by which ABCE proteins in carnations regulate flower development and is of guiding significance for the directional improvement of carnation flower patterns.

    MATERIALS AND METHODS

      Plant materials

    • D. chinensis 'L', a high-generation inbred line, were grown in an experimental field under natural conditions at Huazhong Agricultural University, in Wuhan, Hubei Province, China (30°28'36.5" N, 114°21'59.4" E). Six samples of different organs (stems and leaves during vegetative growth; sepals, petals, stamens, and pistils of flowers) were collected from D. chinensis 'L'. For each biological replicate, the samples were extracted and then immediately frozen in liquid nitrogen and stored at −80 °C until RNA extraction. Arabidopsis plants were grown under long-day conditions (16-h light/8-h dark cycle) at 22/21 °C day/night in an illumination incubator.

      Microscopy and expression profiling analysis

    • Samples from different floral primordium development stages were identified under the microscope. Shoots were fixed and sectioned following previously described methods[25]. Transcriptome samples from six different flower developmental stages were sequenced and obtained (PRJNA574036). The RNA-seq reads were mapped to the new carnation genome[26] using HISAT2[27]. Principal component analysis (PCA) of the samples was performed using the prcomp function in R software. The expression levels of each gene in each RNA-seq library were calculated as the fragments per kilobase of exon model per million mapped fragments (FPKM). The average FPKM value across three biological replicates was calculated and represented in a heatmap.

      Cloning of D. chinensis class E genes

    • Based on transcriptome data (PRJNA533533 and PRJNA574036)[28] and the two published genomes of the carnation[26,29], primers of the D. chinensis class E genes were designed specifically by Primer Premier 5.0 (Supplemental Table S1). Total RNA was isolated from flower buds of D. chinensis 'L' using EASYspin Pant RNA kit reagent according to the manufacturer's instructions. To remove potentially contaminating genomic DNA, RNA was treated with RNase−free DNase (Promega, USA). First strand complementary DNA (cDNA) was synthesized from 1 μg total RNA with the Prime Script TM RT Reagent Kit with gDNA Eraser (Takara, Otsu, Japan) following the manufacturer's instructions. All target fragments were cloned into the pMDTM18−T vector (TaKaRa, China) to transform DH5α Escherichia coli (Shanghai Weidi Biotechnology, China) and sequenced. The plasmids were extracted by Plasmid Miniprep Kit I (Biomiga, USA) and stored at −80 °C. The full-length coding sequences (CDS) of six DcSEP genes are shown in Supplemental Table S2.

      Phylogenetic and alignment analysis of class E genes

    • A total of 52 class E genes from different species, including the AtAP1 gene as an outgroup, were used for phylogenetic analysis (Supplemental Table S3). Protein sequences were obtained from NCBI (www.ncbi.nlm.nih.gov) and previous reports[30]. The amino acid sequences were aligned with the DNAMAN v6.0.x program. A phylogenetic tree was constructed using MEGA v6.0[31] by the neighbor joining (NJ) method with 1,000 iterations for the bootstrap values.

      Gene expression analysis by qRT−PCR

    • Total RNA of each sample was extracted using an EASYspin Plant RNA kit reagent (Aidlab Biotechnologies, Beijing, China) according to the manufacturer's instructions. The specific primers of six DcSEPs for qRT−PCR were designed within the nonconservative C-terminal region using Primer Premier 5.0 software and are listed in Supplemental Table S4. The qRT−PCR was conducted using SYBR Premix Ex Taq (Takara, Beijing, China) and the ABI Prism 7500 Sequence Detection System (Applied Biosystems, Beijing, China). Each PCR was performed with three biological and three technical replicates. The housekeeping gene DcGAPDH was selected as an internal quantitative control (Supplemental Table S4). The relative expression values were calculated using the comparative CT(2−ΔΔCᴛ) method[32].

      Paraffin section

    • Floral buds were divided into six developmental stages: Stage 1 (S1): the stage of floral initiation, S2: sepal primordium development stage, S3: petal primordium development stage, S4: stamen primordium development stage, S5: carpel primordium development stage, S6: late stage of differentiation of floral organ primordium. Samples of different flower bud differentiation stages were fixed overnight in fresh FAA (3.7% formaldehyde, 5% acetic acid, and 50% ethanol). Samples were finally embedded in paraffin for subsequent use of tolonium chloride as a dye. After the sections were sliced, they were observed and photographed under a Jiangnan NLCD500 microscope (Jiangnan, Nanjing, China).

      Yeast two-hybrid assays

    • The GAL4-based Matchmaker Two-Hybrid System (Clontech) was used. Every full-length ORF of class E genes from D. chinensis was fused into pGADT7 or pGBKT7 to form the prey or bait constructs, respectively. The bait and prey plasmids were cotransformed into yeast strain AH109 and spotted on medium lacking leucine and tryptophane (SD/–Leu–Trp, Coolaber, Beijing, China). Protein interactions were tested on SD/–Leu–Trp–His–Ade plates (Coolaber, Beijing, China). X-α-Gal (5-Bromo-4-chloro-3-indolyl-α-Dgalactopyranoside) was used as a substrate to quantify the interaction affinity. Each combination was gradient diluted separately. To confirm the reliability of the results, at least three individual clones were used for each combination. The primers used were listed in Supplemental Table S5.

      BiFC

    • To verify the reliability of the yeast two-hybrid assay results, the CDSs of DcSEP1 and DcSEP3-1, DcSEP3-2, DcSEP4-1 and DcSEP4-2 (without stop codon) were amplified with the primers (Supplemental Table S6) and cloned into the pGBKT7-gene and pGADT7-gene separately to create DcSEP4-2-YFPN, DcSEP1-YFPC, DcSEP3-1-YFPC, DcSEP3-2-YFPC and DcSEP4-1-YFPC constructs. The constructs carried by Agrobacterium tumefaciens GV3101 were used for the transfection of 5-week-old Nicotiana benthamiana leaves, according to the protocol described by Walter et al.[33]. After 2-day culture, the samples were observed with a fluorescence microscope (LEICA, DM2500).

      Plant transformation

    • The pMD18-T vectors containing CDS of DcSEP3s genes were digested by restriction enzymes, and the target fragments were ligated into the corresponding sites of vector, modified from the binary vector pCAMBIA2300 containing the CaMV35S promoter, resulting in 35S:DcSEP3-1 and 35S:DcSEP3-2 constructions, respectively. All the constructed plasmids were confirmed by PCR and sequenced. The resulting plasmids were then transformed into the A. tumefaciens strain GV3101. The floral dip method in Arabidopsis was carried out as previously described[34]. The transformed seeds were screened on Murashige and Skoog (MS) agar with 50 μg·ml−1 kanamycin and 50 μg·ml−1 cefotaxime. T2 plants were used in this study.

      Statistical analysis

    • Statistical significance was checked using GraphPad Prism version 9.0 for one-way ANOVA. And significant difference was shown at p < 0.01 (**).

    RESULTS

      High-quality transcriptome sequencing of developing floral organ primordium in D. chinensis

    • The floral organ primordium of developing D. chinensis 'L' was divided into six typical stages: Stage 1 (S1): the stage of floral initiation, S2: sepal primordium development stage, S3: petal primordium development stage, S4: stamen primordium development stage, S5: carpel primordium development stage and S6: late stage of differentiation of floral organ primordium (Fig. 1a). The total RNA was isolated from the flowers of the six stages and sequenced using the Illumina platform, generating more than 21 million high-quality reads representing more than 6 Gbp in every sample. (Supplemental Table S7). Q30 values (sequencing error rate < 1%) ranged from 89.95% to 95.47%. The PCA plot showing clustering of three biological replicates of different stages of flower development was high, indicating that the dataset was reliable (Fig. 1b). Based on the recently published carnation genome[26], we aligned the sequencing reads to the reference genome and calculated the expression levels (FPKM) (Fig. 1c). The results showed that there were more than 2,000 genes with FPKM values > 60, more than 6,000 genes with FPKM values between 15 and 60, and more than 20,000 genes with FPKM values < 1 in each sample (Supplemental Table S8).

      Figure 1. 

      Transcriptome sequencing of flowers at different floral organ primordium developmental stages in D. chinensis. (a) Floral organ primordium at different developmental stages. (b) Principal component analysis (PCA) analysis of different samples. (c) The expression in floral organ primordium at different stages. S1: the stage of floral initiation. S2: Sepal primordium development stage. S3: Petal primordium development stage. S4: Stamen primordium development stage. S5: Carpel primordium development stage. S6: Late stage of differentiation of floral organ primordium. br. bract; se. sepal; pe. petal; st. stamen; ca. carpel.

      Dynamic comparative analysis of differentially expressed genes (DEGs) during floral organ primordium development

    • We conducted a comparative analysis of the DEGs using five combinations of stages that represented major changes in floral organ primordium development (S2_vs_S1, S3_vs_S2, S4_vs_S3, S5_vs_S4 and S6_vs_S5). There were 976 (S2_vs_S1), 1,398 (S3_vs_S2), 1,335 (S4_vs_S3), 1,521 (S5_vs_S4), and 410 (S6_vs_S5) upregulated DEGs identified, and 411, 1,539, 966, 1,792, and 845 down-regulated DEGs identified, respectively (Fig. 2a). Among them, MADS-box genes were only present in upregulated DEGs with floral organ primordium development. Especially during the first three developmental stages (S2–S4) after flower initiation (S1), there were a greater number of MADS-box DEGs (Fig. 2b). In contrast to other MADS-box genes, we found that class E genes were only differentially expressed in the first two comparison groups (S2_vs_S1, S3_vs_S2) (Fig. 2c), which suggested that class E genes may play important roles in the development of the sepal primordium and petal primordium.

      Figure 2. 

      Analysis of differential expression genes in different floral organs primordium development stages. (a) Bar graph showing differential expression genes (DEG) number of up-regulated and down-regulated in different pair comparisons (S2_vs_S1, S3_vs_S2, S4_vs_S3, S5_vs_S4 and S6_vs_S5). (b) The number of ABCE class MADS-box genes with differentially expressed in different comparison. (c) The DEGs of class E genes in each different comparison are displayed. Red represents up-regulated genes and blue represents down-regulated genes.

      Identification and evolutionary analysis of DcSEP genes

    • Based on the MADS-box genes identified from two carnation genomes, genome_v0 and genome_v1[26,29], we identified the known class ABCE genes and found that the number of class ABC genes was the same in the two carnation genomes. The number of class E genes was six in genome_v0[29] published in 2014 and five in genome_v1 published in 2022[26]. To further confirm the members of class E genes in D. chinensis, the E genes were amplified using cDNA from D. chinensis as a template. Then, six DcSEP genes were identified and amplified in D. chinensis. Finally, a total of 15 full-length ABCE genes were obtained. Then, a phylogenetic tree was constructed by using the MADS-box proteins from D. chinensis and other species (Fig. 3). Referring to the naming of D. caryophyllus proteins[30], the corresponding D. chinensis genes were designated AP1 (DcAP1), FUL (DcFUL), AP3 (DcAP3-1 and DcAP3-2), PI (DcPI and DcPI2), TM6 (DcTM6), AG (DcAG1 and DcAG2), and SEP (DcSEP1, DcSEP3-1, DcSEP3-2, DcSEP4-1, DcSEP4-2, and DcSEP4-3).

      Figure 3. 

      The phylogenetic tree of the class A-, B-, C- and E- proteins. The subgroups are indicated by different colors.

      To further identify the subclade of class E genes, these class E amino acid sequences were aligned which showed that they all had the conserved MADS domain and K domain as well as the typical SEPI and SEPII terminal motifs (Supplemental Fig. S1). The similarity of these class E amino acid sequences in D. chinensis and D. caryophyllus was between 95.86 and 100% (Supplemental Table S9). In addition, we found that the number of class E genes in different published species was different (Table 1, Supplemental Fig. S2). Among them, the number of both SEP1/2/4 and SEP3 subgroup members varied, such as in the SEP3 subgroup, three members in B. rapa, two members in Triticum aestivum and only one member in Citrullus lanatus and P. mume. This result indicated the difference in class E genes among different species.

      Table 1.  The number and references of class E homologous genes in different species.

      SpeciesE genesSEP1/2/4
      subclass      		SEP3 subclassReference
      C. lanatus211[13]
      P. mume431[14]
      O. sativa532[15]
      B. rapa1073[16]
      A. thaliana431[4−6]
      T. aestivum862[35]
      D. caryophyllus642[30]
      D. chinensis642This study

      Expression of the genes related to flower development in D. chinensis

    • To investigate the molecular mechanism underlying floral organ identity, the expression patterns of these genes were assayed using transcriptome data and qRT–PCR (Fig. 4). We applied the FPKM value obtained via transcriptome profiling to generate a heatmap for the DcMADS-box gene expression patterns during floral development (Fig. 4a). The results revealed that DcAP1 and DcFUL1 were expressed at the early stage of floral development (S1), in which the shoot apical meristem (SAM) transformed into flower meristem and the bract primordium differentiated, and their expression level increased gradually with the development of floral organs. Regarding class B, DcPI and DcPI2 (PI homologs), DcAP3-1 and DcAP3-2 (AP3 homologs), and DcTM6 were all expressed from the petal primordium at stages 3–6, but the expressions of DcAP3-1 and DcPI2 were low and their expression level increased from S4. DcAG1 began to be expressed after flowering initiation (S1), but DcAG2 began to be expressed after the emergence of the stamen primordium (S4). DcSEP3-1 was expressed in sepal and petal primordia at stages 3 and 4, while DcSEP3-2 had lower expression than DcSEP3-1, and its expression activation stage was later than that of DcSEP3-1. The expression pattern of DcSEP4-2 was similar to that of class A genes and DcSEP1 and they are grouped together. The expression pattern of DcSEP4-1 was similar to that of DcSEP3-2 and expressed from petal primordium development. Overall, ABCE genes exhibited dynamic expression patterns in different flower development stages. In addition, the qRT–PCR results also showed that the gene expression patterns of class E genes were different in the tissues and organs of D. chinensis (Fig. 4b–c).

      Figure 4. 

      Analysis of expression in D. chinensis E class genes at different tissues and stages. (a) The spatial expression patterns of class E genes in developing flowers of D. chinensis as revealed by RNA-seq. (b) The expression of six class E genes of D. chinensis in different organs were detected by qRT–PCR. Error bars indicate the collective standard deviations of three biological replicates and three technical replicates. se, sepal. pe, petal. st, stamen. ca, carpel. ste, stem. le, leaf. (c) The different organs of D. chinensis.

      Protein interaction of class E genes in D. chinensis

    • To clarify how homologous or heterologous dimers can be formed among six class E proteins and other MADS-box proteins in D. chinensis, the yeast two-hybrid method was used in this study to analyze the interaction patterns of these proteins (Fig. 5 and Supplemental Fig. S3). None of the selected proteins were self-activated (Supplemental Fig. S4).

      Figure 5. 

      The interaction statistics of class E proteins with other class A−, B−, C genes in D. chinensis. '+' in light orange represents weak interaction; '++' in orange represents moderate interaction; '+++' in deep orange represents relatively strong interaction; '++++' in brown represents strong interaction; '−' in bule represents that there is no detectable interaction of proteins, '\' in grey represents did not cover in this study.

      The results showed that the class E proteins DcSEP3-1, DcSEP3-2, DcSEP4-2 and DcSEP4-3 interacted with more proteins than DcSEP1 and DcSEP4-1 (Fig. 5 and Supplemental Fig. S3). The DcSEP3-1 protein interacted with one class A protein (DcAP1), while DcSEP3-2 and DcSEP4-3 interacted with the other class A protein (DcFUL1). DcSEP4-2 interacted with two class A proteins. DcSEP4-2 lightly interacted with DcAP1 and had a relatively strong interaction with DcFUL1. Four class E proteins (DcSEP3-1, DcSEP3-2, DcSEP4-2 and DcSEP4-3) all interacted with DcPI and DcPI2 of class B. Among them, DcSEP3-2 still interacted with DcTM6 of class B, and DcSEP4-2 interacted with DcAP3-1. For the interaction with class C genes, DcSEP3-1, DcSEP3-2, DcSEP4-2 and DcSEP4-3 all interacted with DcAG1 and DcAG2. Moreover, the proteins of class E not only interacted with class A-, B- and C- proteins but also, they interacted with their own proteins to form homologous dimers, such as DcSEP3-1, DcSEP3-2, DcSEP4-2 and DcSEP4-3 (Fig. 5 and Supplemental Fig. S3). To verify the reliability of the results, four combinations of DcSEP4-2 interactions with other proteins (DcSEP1, DcSEP3-1, DcSEP3-2 and DcSEP4-1) were selected for BiFC experiments (Supplemental Fig. S5) and showed similar results to those of Y2H, suggesting that the two methods being mutually supportive. Overall, compared other subclade, the interactions of the SEP3 subclade were the richest in all the protein interactions of class E genes. It is speculated that SEP3 subclade functions are more important. Moreover, the two genes (DcSEP3-1 and DcSEP3-2) belong to the same subclade have different interaction patterns, which suggesting that they play different roles in flower development.

      DcSEP3s of D. chinensis play different roles in the regulation of flower development

    • To further investigate the roles of the two DcSEP3s in flower development, the constructed vectors containing DcSEP3-1 and DcSEP3-2 were transformed into Arabidopsis. Transgenic plants were obtained by screening. The relative gene expression levels of these transgenic plants and wild-type Arabidopsis were analyzed (Fig. 6). Ectopic expression of DcSEP3-1 and DcSEP3-2 strongly influenced flowering time and plant architecture. Phenotypic analysis of transgenic lines showed that overexpression of DcSEP3-2 genes in Arabidopsis resulted in early flowering, smaller rosettes, dwarfism, abnormal floral organs and the number of rosette leaves decreased significantly compared with the wild type (Fig. 6 and Supplemental Figs S6 & S7). The transgenic line overexpressing DcSEP3-1 only showed an early-flowering phenotype (Fig. 6 and Supplemental Fig. S7). All these results further suggested that two DcSEP3 genes of D. chinensis were sub-functionalized.

      Figure 6. 

      Phenotype and expression analysis of D. chinensis class E genes overexpression in A. thaliana. (a) Transgenic plant of 35S:DcSEP3-1 (left), Columbia (Col) Arabidopsis (right). (b) Transgenic plant of 35S:DcSEP3-2. (c) Expression of DcSEP3-1 in transgenic lines. (d) Expression of DcSEP3-2 in transgenic lines. Data represent the mean ± SE from three biological replicates, and AtEF1a was used as internal control. Significant difference was shown at p < 0.01 (**).

    DISCUSSION

    • Class E genes play significant roles in floral organ development, and every whorl of floral organ formation is regulated by at least one SEP protein[7,36]. In our results, the expression patterns of the six class E genes were different not only at different floral organ primordium developmental stages, but also in different tissues based on the transcriptome data and qRT–PCR analysis. For example, DcSEP1 and DcSEP4-2 were expressed from the S2, and DcSEP3-1 was expressed from the S3. DcSEP1 was highly expressed in petals and carpels which was similar to that of GRCD3 in Gerbera hybrida[37] and SlaSEP1 in Silene latifolia[38], while, DcSEP3-1 was highly expressed in sepals, petals, and carpels. In addition, through evolutionary analysis, the expression patterns of genes in the same subclade may be the same or different, which indicates that the evolution of class E genes in D. chinensis is complex. Especially, the expression pattern of the DcSEP3-2 gene was different from that of DcSEP3-1, and it was mainly detected in sepals and petals, although they were all SEP3 homologs. This was different from what has been reported in Arabidopsis; AtSEP3 was mainly expressed in the inner three whorls, and the expression level was highest in petals[9]. Besides, we found that the transgenic lines of same subclade genes also showed different phenotype, such as the transgenic lines overexpressing DcSEP3-1 and DcSEP3-2. The results suggested that the two DcSEP3 genes of D. chinensis were subfunctionalized. A similar phenomenon has been found in other species. For example, in the woody plant Platanus acerifolia, overexpression of PlacSEP3-1 in Arabidopsis showed slightly early flowering or slightly more cauline leaves, unlike PlacSEP3-2, which showed severe phenotypic changes[39]. In marigold, overexpression of TeSEP3-2 and TeSEP3-3 led to early flowering in Arabidopsis, which was different from that of TeSEP3-1[40]. These reports have shown that genes in the same subclade may undergo subfunctionalization. In addition, different subclades may have undergone multiple evolutionary events. For example, in G. hybrida, GhGRCD5 plays a unique role in regulating petal development, while, GhGRCD1 regulates stamen development[41]. In addition, in orchids, overexpression of the PeSEP3 gene leads to transgenic Arabidopsis plants showing severe phenotypes, such as early flowering and much smaller plant size, while overexpression of PeSEP1 shows no obvious change in phenotype[20].

      In addition to the comparison of gene expression patterns and transgene experiments to predict whether the gene form the same subclade has been subfunctionalized, the pattern of protein interaction belonging to the same subclade is also good evidence. Previous studies have found that functionally redundant proteins have the same interaction pattern and may have shared interaction partners when performing their function[42,43]. For example, in Arabidopsis, there is functional redundancy between AtSEP1 and AtSEP3 proteins, and the interaction patterns of these two proteins are extremely similar[44]. In our study, the interaction patterns of different subclades showed a variety of results: DcSEP3-1 and DcSEP3-2 had different interaction patterns. The protein interaction patterns of DcSEP4-1 were different from that of DcSEP4-2 and DcSEP4-3, while DcSEP4-2 had a similar interaction pattern with DcSEP4-3. In our results, we found that DcSEP3-1 and DcSEP3-2 were different not only in their interaction patterns but also in their expression patterns and gene functions. Therefore, we speculate that the two genes belonging to the SEP3 subclade in Dianthus may experience sub-functionalization. However, the genes belonging to other subclades showed more complex patterns of interaction, such as the DcSEP4 subclade, and there is much work to be done to elucidate which evolutionary events these genes have undergone.

      Acknowledgments

      • This work was supported by the National Natural Science Foundation of China (No.32072607).

      Conflict of interest

      • Xiaopeng Fu is the Editorial Board member of journal Ornamental Plant Research. She was blinded from reviewing or making decisions on the manuscript. The article was subject to the journal's standard procedures, with peer-review handled independently of this Editorial Board member and her research group.

      • # These authors contributed equally: Xiaoni Zhang, Quanshu Wu

      Supplementary information
      Rights and permissions
      • Copyright: © 2023 by the author(s). Published by Maximum Academic Press, Fayetteville, GA. This article is an open access article distributed under Creative Commons Attribution License (CC BY 4.0), visit https://creativecommons.org/licenses/by/4.0/.
    Figure (6)  Table (1) References (44)
  • About this article
    Cite this article
    Zhang X, Wu Q, Lin S, Li D, Bao M, et al. 2023. Identification and characterization of class E genes involved in floral organ development in Dianthus chinensis. Ornamental Plant Research 3:5 doi: 10.48130/OPR-2023-0005
    Zhang X, Wu Q, Lin S, Li D, Bao M, et al. 2023. Identification and characterization of class E genes involved in floral organ development in Dianthus chinensis. Ornamental Plant Research 3:5 doi: 10.48130/OPR-2023-0005
    shu

Catalog

  • Html

  • Introduction
  • Materials and methods

  • Plant materials

  • Microscopy and expression profiling analysis

  • Cloning of d. chinensis class e genes

  • Phylogenetic and alignment analysis of class e genes

  • Gene expression analysis by qrt−pcr

  • Paraffin section

  • Yeast two-hybrid assays

  • Bifc

  • Plant transformation

  • Statistical analysis

  • Results

  • High-quality transcriptome sequencing of developing floral organ primordium in d. chinensis

  • Dynamic comparative analysis of differentially expressed genes (degs) during floral organ primordium development

  • Identification and evolutionary analysis of dcsep genes

  • Expression of the genes related to flower development in d. chinensis

  • Protein interaction of class e genes in d. chinensis

  • dcsep3s of d. chinensis play different roles in the regulation of flower development

  • Discussion
  • Acknowledgments
  • Conflict of interest
  • Supplementary information
  • Rights and permissions
  • About this article
logo

Contents

Policies

Services

Partnerships

© 2025 Maximum Academic Press, except Open Access articles. MAP is a member of ALPSP, COPE, CrossRef, cOAlition S, OASPA and STM.

Privacy Policy  |  Site Map  |  Terms and Conditions

/

DownLoad:  Full-Size Img  PowerPoint
Return
Return