The Influence And Mechanism Study Of Combined Treatment Of Salt And MeJA On Plant Growth In Arabidopsis Seedlings

Numerous studies have demonstrated the separate effects of salinity and jasmonic acid(JA) on plant growth and senescence, but the combined effect of them is still unclear. In this study, we explored the mechanism of the combined effect by comparing the physiology and biochemistry in Arabidopsis and expression analysis under combined treatment(N+M) and separate treatment of Na Cl or Me JA. The Main results are as follows:(1) We detected indexes such as primary root lengths after the combined treatment(N+M) or separate treatment of Na Cl or Me JA, respectively. The results showed that compared with the single treatment of Na Cl or Me JA, N+M could more obviously inhibit plant growth, reduce chlorophyll content and primary root length, and it was does-dependent.(2) The detection results of Fpro, MDA and reactive oxygen showed that compared with separate treatment, N+M could induce O2- accumulation and up-regulate MDA and Fpro contents. These indicated that N+M treatment could cause more reactive oxygen and damage in plant.(3) Through the results of dark treatment of excised leaves, and analyses of TB staining and senescence related gene expressions, we found that compared with separate treatment, N+M could cause more serious chlorosis in darkness, more darker TB tinting and promote the transcripts of senescence related genes, especially SAG13. These results indicated that N+M could induce faster leaf senescence.(4) In JA-insensitive mutants, includingjar1-1, jin1-9 and coi1-30, growth inhibition and senescence acceleration caused by N+M were significant weaker than those in WT, but still showed obvious differences compared with those in the control. These indicated that N+M is partially-dependent on JA signaling during aggravating plant inhibition and leaf senescence.(5) We detected the expression of JA biosynthesis(AOS, AOC2) and response(VSP1, VSP2) related genes by q RT-PCR. Compared with Na Cl or Me JA treatment, N+M could more obviously up-regulate transcripts of AOS, AOC2, VSP1 and VSP2, and the inducible multiple was much higher than the sum of those caused by Na Cl and Me JA. These indicated that N+M could amplify JA signal in plant.(6) JA could induce synthesis of secondary metabolite-glucosinolate(GS). The q RT-PCR results of genes related to the indole-glucosinolate(IG) and aliphatic-glucosinolate(AG) synthesis showed that N+M could more significantly induce the transcripts of genes involved in IG synthesis than that of AG. Furthermore HPLC analysis showed that N+M could cause more endogenous IG accumulation than that of AG. All these results demonstrated that N+M could induce IG accumulation dependent on amplified JA signal in plant.(7) We used N+M or single Na Cl or Me JA to treat DR5::GUS transgenetic plants and ABA related mutants. GUS staining results showed differences between N+M and single treatment of Na Cl or Me JA. The growth, chlorophyll content and root length showed no differences in ABA related mutants and WT. These results indicated that the response of Arabidopsis to N+M stress might be related to auxin signaling, but was independent of ABA signaling.(8) Na Cl and mannitol are usually used to mimic common abiotic stress, while SA and Me JA have more important functions in biotic stress. We used different combinations of them(M+M, N+S) to treat plants and discovered similar phenotypes and some physiological indexes compared with those caused by N+M. These results indicated that combined treatment of abiotic and biotic stresses might share common signaling pathway.