Effects Of Methyl Jasmonate On Physio-Biochemical Characteristics And Genes Expression Of Cotton Under Drought Stress

With the deterioration of the global nature of the ecological environment,desertification and salinization of the land become seriously. Because of the soil erosion and natural destory, water resource scarcity has become a fearful ecological problems. Drought directly impact of the developing ability of plant, also make the crop failures.Jasmonates contains jasmonic acid, methyl jasmonate and its derivatives are involved in plant of different developmental processes, such as germination, root grow,senescence, fruit ripe et al. Numerous studies demonstrate that MeJA has been identified as a key signaling substance activate plant defense mechanism responses against stress.The target of the research was to detect the seed germination, physiological and biochemical and analyze the major parameter in response to salt and drought stress of cotton ‘XLZ17’ an widely plant in Xinjiang. The GhJMT gene which was encoded the Jasmonic acid carboxyl methyltransferase was isolated from the ‘XLZ17’, constructed with pCAMBIA2300 then transformed into tobaccos. Finally, VIGS was used to silence the GhJMT. Our study was designed to provide theoretical basis for the application of MeJA in the cotton production.(1) Under 300 mmol/L NaCl and 23%PEG6000, the effects of JA and MeJA pretreatment were detected. Combined with our results this desmonstrated that JA and MeJA in a certain concentration could effectively mitigate inhibitory effect under drought and salt stress and improve the cotton seed germination and seedling growth.In general, the ability for alleviation to drought stress by MeJA pretreatment was better than JA.Under drought, 0.25 and 2.5 μmmol/L JA were the optimum pretreatment concentration for seed growing, and for MeJA was 2.5 μmmol/L. While,0.025 μmol/L JA and 0.25 μmol/L MeJA were the optimum pretreatment concentration for seed germination in salt stress. 0.25 and2.5 μmmol/L JA and MeJAwere the best pretreatment concentration for seeding growth.(2) Under drought treatment, the effects of exogenous MeJA and its inhibitor SHAM were measured on water content, photosynthesis, osmoconditioning system,antioxidant response and membrane destory in cotton. The results indicated that 2.5μmol/L MeJA treatment significantly increased the relative water content by 22.11%,total chlorophyll content to 40.58%, also the contents of betaine, soluble sugur and proline were remarkably increased, which result in reducing the osmotic potential by20.29%. while AsA content, activity of SOD and CAT increased by 38.19%, 28.54%and 46.19%, respectively, as well as decreased O2- and H2O2 content by 43.71% and84.85%, make for MDA content and RC remarkably decreased. When added MeJA inhibitors SHAM, physiological and biochemical indicators showed that the plants suffer more serious injuries. Combined with our results this demonstrated that MeJA could effectively mitigate inhibitory effect, alleviate the osmotic stress and oxidative stress that made by drought, which provided a scientific basis for the application of MeJA in the cotton production.(3) According to the transcriptome of Asian cotton Shixiya I(Gossypium arboretum), a cDNA fragment was isolated from upland cotton cultivar ‘XLZ17’. The cDNA was named as jasmonic acid carboxyl methyltransferase of cotton(GhJMT).Bioinformatics analysis indicated that GhJMT contains an open reading frame of 1116 bp,that encodes 371 amino acids. Conserved domain analysis showed that GhJMT has a conserved domain of methyltransferase-7. Phylogenetic tree analysis showed that GhJMT was closer to the Theobroma cacao, which was an unstable hydrophilic proteins sub-cellularly cytoplasm. qRT-PCR indicated that drought stress could induce the GhJMT expression. The GhJMT gene was constructed in nd then it was constructed pCAMBIA2300 then transformed into tobaccos using agrobacterium-mediated procedure. PCR and RT-PCR showed that 5 plants were positive. The successed expression of GhJMT in tobacco, would help to clarify the relationshipbetween GhJMT expression and plant resistance.(4) A 450 bp fragment was gained according the GhJMT by RT-PCR, which was connected with viral vector pTRV-RNA2. After transformed into the Agrobacterium,VIGS was used to interfere the GhJMT. The results indicated that, although the positive control(CLA1) was able to silence expression induced by VIGS, the positive success rate of the test was only 16.7%. Therefore, it could not effectively judge whether the GhJMT gene silenced the experimental group, which needed to further grope the experimental requirement.