G protein and PLDδ are involved in JA to regulate osmotic stress responses in Arabidopsis thaliana

Jasmonic acid (JA) is regarded as an endogenous regulator which plays an important role in regulating plant growth, development and stress response. Using the seedlings of A. thaliana ecotype Col-0 (wild-type, WT), phospholipase D delta (PLD delta) deficient mutant (pld delta), the G protein a subunit (GPA1) deficient mutant (gpa1-4), 9-Lipoxygenase (9-LOX) deficient mutants (lox1 and lox5) as materials, the effects of JA responding to osmotic stress and the functions of G protein and PLD delta in this response were investigated. The results showed that GPA1 involved in the regulation of JA to PLD delta under osmotic stress. Both GPA1 and PLD delta participated in the regulation of JA on the seed germination and osmotic tolerance. Exogenous MeJA reduced the EL and MDA in WT, but increased the EL and MDA in gpa1-4 and pldd, indicating that GPA1 and PLD delta were involved in the protection of JA on the membrane. The genes expression levels, and the activities of PLD delta and LOX1 were significantly induced by osmotic stress. The LOX activity and JA content in pldd seedings were lower obviously than those in WT, but were markedly increased and were higher than WT after applying phosphatidic acid (PA). These results demonstrated that JA responded to osmotic stress by regulating G protein and PLD delta in A. thaliana. PLD delta was located upstream of 9-LOX and involved in the JA biosynthesis.