Salt stress response in Arabidopsis thaliana plants with defective jasmonate signaling

The effects of exogenous jasmonic acid (JA) on antioxidant enzymes in four-week-old leaves of wild-type Arabidopsis thaliana L. (Columbia-0) and jin1 (jasmonate insensitive 1) mutant plants with defective jasmonate signaling were investigated under normal conditions and under salt stress (200 mM NaCl, 24 h). The wild-type plants responded to JA by an increase in the activities of Cu/Zn superoxide dismutase, catalase, and guaiacol peroxidase, while there was no change in the case of the mutant plants. In response to the salt stress of both the wild-type and mutant genotypes, the activities of superoxide dismutase, catalase, and guaiacol peroxidase were unchanged, decreased, and increased, respectively. The JA-treated wild type plants showed the highest activity of all three enzymes as compared with the mutant plants. Salinity caused a decrease in chlorophyll content in the wild-type and jin1 plants. Preliminary JA treatment of the Col-0 plants resulted in a normal content of photosynthetic pigments after the salt stress, while the positive JA effect was insignificant in the jin1 mutants. It was concluded that the MYC2/JIN1 protein is involved in the JA signal transduction and plant adaptation to salt stress.