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Figure 1. 

Phylogenetic relationships, multiple sequence alignment, and protein structure of MdSAT1. (a) Phylogenetic tree of SAT1 sequences; the number on each branch represents the genetic distance. (b) Predicted bHLH 3D structure of MdSAT1 protein. (c) Predicted protein secondary of MdSAT1 bHLH structural domain.

Figure 2. 

Nitrogen response of MdSAT1. (a) Shoot and (b) root response of MdSAT1 to KCl (represents 0 N), KNO₃ (represents nitrate), and NH₄Cl (represents ammonium). Error bars represent standard deviation (n = 3). Different letters above the bars indicate significantly different values (P < 0.05).

Figure 3. 

MdSAT1 regulates ammonium uptake and plant growth MdSAT1-OE and Col plants grown for four weeks under low $\text{NH}^+_4 $ (0.5 mM NH₄Cl) or high $\text{NH}^+_4 $ (5 mM NH₄Cl) conditions. (a) Morphological changes, (b) fresh weight, and (c) ammonium content are presented. (d) RT-PCR analysis of AtAMF1;1, AtAMF1;2, AtAMF1;3, AtAMT1;1, AtAMT1;3 and AtAMT1;5 expression in MdSAT1-OE and Col Arabidopsis. Error bars represent the standard deviation (n = 3). Different letters above the bars indicate significantly different values (P < 0.05).

Figure 4. 

MdSAT1 regulates root system conformation MdSAT1-OE and Col plants grown for seven days under low $\text{NH}^+_4 $ (0.5 mM NH₄Cl) or high $\text{NH}^+_4 $ (1.5 mM NH₄Cl) conditions. (a), (b) Morphological changes, (c) primary root length and (d) lateral root number are presented. Error bars represent the standard deviation (n = 3). Different letters above the bars indicate significantly different values (P < 0.05).

Figure 5. 

MdSAT1 regulates root hair growth and development MdSAT1-OE and Col plants grown for three days under low $\text{NH}^+_4 $ (0.5 mM NH₄Cl) or high $\text{NH}^+_4 $ (1.5 mM NH₄Cl) conditions. (a), (b) Morphological changes, (c) root hair number and (d) root hair length are presented. Error bars represent the standard deviation (n = 3). Different letters above the bars indicate significantly different values (P < 0.05).

Figure 6. 

MdSAT1 regulates the expression of genes related to root hair development Analysis of root hair development-related gene expression by RT-PCR under low $\text{NH}^+_4 $ (0.5 mM NH₄Cl) or high $\text{NH}^+_4 $ (1.5 mM NH₄Cl) conditions: (a) AtEGL3, (b) AtTTG1, (c) AtGL3, and (d) AtSCM are presented. Error bars represent the standard deviation (n = 3). Different letters above the bars indicate significantly different values (P < 0.05).

Figure 7. 

MdSAT1 regulates ROS accumulation Col and MdSAT1-OE plants grown for four weeks under low $\text{NH}^+_4 $ (0.5 mM NH₄Cl) or high $\text{NH}^+_4 $ (5 mM NH₄Cl) conditions. (a) NBT staining, (b) MDA content, (c) OFR concent, (d) POD activity, (e) CAT activity, and (f) SOD activity are presented. Error bars represent the standard deviation (n = 3). Different letters above the bars indicate significantly different values (P < 0.05).