Action of methyl jasmonate and salt stress on antioxidant system of Arabidopsis plants defective in jasmonate signaling genes

Role of jasmonate signaling in the regulation of stress-protective systems in Arabidopsis under salt stress remains insufficiently studied. For its clarification, comparative studies with mutants lacking various protein components of jasmonate signaling are advisable. In this connection, effects of methyl jasmonate (MJ, 50 μM) and salt stress (NaCl, 150 mM) on functioning of antioxidant and osmoprotective systems of wild-type Arabidopsis plants (Col-0) and ones defective in jasmonate signaling, namely coi1 (mutant for gene coding the protein COI1, which participates in removal of repressor proteins of transcription factors of jasmonate signaling) and jin1 (mutant defective in gene encoding the transcription factor JIN1/MYC2, one of the key in jasmonate signaling), were investigated. Salt stress inhibited growth of plants of all three genotypes. Treatment with MJ before salt stress positively influenced only the growth of wild-type plants. In contrast to mutants coi1 and jin1, Col-0 plants treated with MJ, under conditions of salt stress, kept close to the control values of water and total chlorophylls content, and the content of carotenoids increased. The coi1 plants under normal conditions differed from wild-type plants and jin1 mutants by reduced activity of guaiacol peroxidase and catalase and increased proline content. Treatment with MJ did not affect the activity of antioxidant enzymes and proline content in both mutants defective in jasmonate signaling. Under salt stress, the activity of superoxide dismutase, catalase and guaiacol peroxidase, as well as the content of proline and anthocyanins, in wild-type plants treated with MJ, were significantly higher than in control plants. The role of jasmonate-dependent protective systems in resistance of Arabidopsis plants to salt stress is discussed.