Figure 6.

ROS production and SA biosynthesis form a self-amplifying feedback loop in Ghlmm. A, Expression of genes regulating to SA biosynthesis were induced by H₂O₂ treatment. The experiments were performed with the wild-type plants. GhEDS1 and GhPAD4 are genes positively regulating SA biosynthesis; GhPAL encodes a catalytic enzyme for SA biogenesis. B, GhEDS1, GhPAD4, and GhPAL were constitutively up-regulated in Ghlmm plants relative to W0. C, CAT (catalase, inhibited by SA) enzyme activity was significantly inhibited in leaves and stems of Ghlmm plants. D, Treatment with AIP, a SA biosynthesis inhibitor, reduced the ROS content and eliminated the cell death phenotype in Ghlmm. AIP is a highly specific inhibitor of PAL enzyme. Bars = 50 μm. E, After treatment with AIP, SA content in Ghlmm decreased to the wild-type level. At least three biological replicates were performed in each experiment. *P < 0.05 and **P < 0.01 (Student’s t test). Different letters (A, B, C) indicate a statistically significant difference at P < 0.01 according to a randomization one-way ANOVA test. Error bars are SE of three biological replicates.