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Figure 1. 

Characterization of MADS-box domain. (a) Multiple sequence alignment of MADS-domain region from 52 PeMADS proteins. (b) Predicted three-dimensional structure of MADS-domain. (c) Distribution of amino acids in conserved residues of MADS-domain: number represents the positions of residues; bottom label represents species of amino acids.

Figure 2. 

Phylogenetic tree of PeMADS proteins from Passiflora edulis (Pe) and Arabidopsis thaliana (At). Red starts and green triangles indicate passion fruit and Arabidopsis, respectively. The circle placed on the tree indicated the bootstrap value (≥ 90, red circle; 60~90, yellow circle; < 60, not shown).

Figure 3. 

The phylogenetic relationship, conserved motifs and gene structures of PeMADSs. (a) The phylogenetic tree of 52 PeMADS proteins. (b) Distribution of conserved motifs in PeMADS proteins. (c) Distribution of MADS-domain and K-domain of PeMADS proteins.(d) The gene structures of the PeMADSs, include coding sequences (CDS) and untranslated regions (UTR).

Figure 4. 

(a) Analysis of cis-elements in the promoter region of PeMADS genes. (b) Heatmap of the number of cis-elements, the different color represents the number of cis-elements. (c) The sum of cis-elements in categories shown as a histogram.

Figure 5. 

Distribution and collinearity of PeMADS genes in the passion fruit genome. PeMADSs marked by red has synteny with other genes. Gray lines indicate synteny blocks in passion fruit genome, brown lines indicate segmental duplicated MADS gene pairs of passion fruit.

Figure 6. 

Synteny analysis of PeMADS genes and five representative plants species. Gray lines in the background indicate the collinear blocks between passion fruit and other plant genomes, while red lines highlight the systemic gene pairs of PeMADSs between passion fruit and other plant genomes.

Figure 7. 

Predicted three-dimensional structures of the passion fruit MADS-box protein sequences.

Figure 8. 

The expression profile of MADS-box genes in floral tissues. (a) The ABC(D)E model in Eudicots, the bottom illustration indicates the gene expression values (bar heights) of ABC(D)E members in passion fruit. (b) Gene expression patterns of MADS-box gene family from floral tissues of passion fruit.

Figure 9. 

qRT-PCR analysis of part members from the ABC(D)E model. (a) Illustration of passion fruit floral structure and summarization of the ABC(D)E model in passion fruit. (b) qRT-PCR results of six representative members from the ABC(D)E model, all experiments were performed independently at least three times. Error bars represent the standard deviation. Asterisks indicate significant differences in transcript levels compared with the early development stage of bract (br1). (* p < 0.05).

Figure 10. 

Expression profiles of PeMADS genes in (a) non-floral organs and (b) under temperature stresses, DPA indicates days post anthesis; '1, 4, 12, 24 h' represents the time of stress treatment. Temperature of 20 °C (T20) is regarded as cold stress, while a temperature of 30 °C is regarded as heat stress (T30). The pink stars highlight the members with specific expression characteristics during fruit development or under temperature treatment.

Figure 11. 

Expression patterns of PeMADS genes in response to phytohormones. Leaf samples were collected at 0, 12, 24 and 48 h after GA and ABA treatments. Significant differences were analyzed by the Student's t-test (* p-value < 0.05, ** p-value < 0.01, *** p-value < 0.001, and **** p-value < 0.0001).