Fig. 6: Arabidopsis SYP7 SNAREs have a conserved role in protecting rehydrating pollen from hypoosmotic shock.

a Phylogenetic relationship of Arabidopsis syntaxins. The tree was generated using the neighbour-joining method in MEGA7. The three members of the SYP7 subgroup are indicated with red dots. b Ectopic expression of SYP7, SYP6, and SYP5 genes under the control of the SYP72 promoter in syp72-1 pollen (n = 10 biologically independent pollen grains). c Analysis of plasma membrane integrity during rehydration of pollen grains from the syp72-1 mutant stably expressing Arabidopsis syntaxin genes SYP71, SYP73, SYP51, or SYP61 under the control of the SYP72 promoter, as observed by PI staining. Scale bars, 50 µm. d Percentages of PI-positive pollen grains from syp72-1 transformed with Arabidopsis syntaxin genes SYP71, SYP73, SYP51, or SYP61. Two independent transgenic lines for each syntaxin gene were used for analysis. Data are the mean ± SD from three independent replicates. PI-positive pollen grains were scored from 300 pollen grains for each replicate. Two-tailed Student’s t test was used for statistical analysis (ns no significant difference, P > 0.05; ****P < 0.0001). e Subcellular localization of MSL8-RFP in the syp72-1 mutant stably expressing different Arabidopsis syntaxin genes. Scale bars, 5 µm. f Profile of relative fluorescence intensity for MSL8-RFP (red line) along a dashed line (labelled in e) drawn across a pollen grain. g The percentages of pollen grains showing MSL8-RFP plasma membrane signals (e) in syp72-1 plants transformed with different Arabidopsis syntaxin genes. Data represent the mean ± SD from three independent experiments, with 60 pollen grains analysed in each experiment (n = 180). Ordinary one-way ANOVA with Tukey’s multiple comparisons test was used for statistical difference analysis between different groups. P < 0.05 was considered statistically significant. Different letters above the bars indicate significant differences between groups. cw cell wall, pm plasma membrane.