Effects Of Ectopic Expression Of GhMAC3 On Drought And Heat Resistance In Arabidopsis Thaliana

Abiotic stresses such as drought affect plant growth which result in reduction of crop yield.The ubiquitin proteasome pathway(ubiquitin/26S,proteasome,pathway)is one of the most important and highly selective protein degradation pathways in plant.In this way,the protein was marked by ubiquitin under the catelysis of ubiquitin activating enzyme(ubiquitin-activating enzyme,El),ubiquitin conjugating enzyme(ubiquitin-conjugating enzyme,E2)and ubiquitin ligase(ubiquitin-protein ligase,E3),namely ubiquitination Proteins marked by polyubiquitination can be identified and degradation,E3 ubiquitin ligase plays a crucial role in specific recognition substrate,ubiquitination-mediated protein degradation system is involved in almost all aspects of plant biological processes,including in response to abiotic stresses.GhMAC3 is a gene identified in a lintless-fuzzless mutant of Xuzhou 142 that encodes a E3 ligase containing PrP19/WD40/U-box domains,the function of this gene has not been reportd.promoter analysis shows that there are 3 cis-elements in response to drought stress including 2 ABREs and 1 MYB binding site MBS and 3 HSEs in response to heat shock in the uptream swuence of GhMAC3,suggesting that this gene may be involved in the regulation of plant responses to drought and heat stress.In the current thesis,the transgenic Arabidopsis lines overexpressing GhMAC3 were used as research materials,the copy numbers of transgenes,drought and heat stress resistance,physiological parameters of drought resistance,exprsession levels of drought resistance related genes,and differentially expressed proteins were analysed,and the results shows that overexpressing GhMAC3 could significantly improve drought and heat resistance of Arabidopsis thaliana,the mechanism of drought resistance conferred by GhMAC3 gene was preliminarily elucidated.The main results are as follows(1)By using fluorescence quantitative PCR,the copy number of transgenes in Arabidopsis overexpressing GhMAC3 was 2,GhMAC3 was highly expressed in transgenic Arabidopsis.(2)Ectopic overexpression of GhMAC3 significantly improved the whole-growth-period resistance to heat and drought resistance in Arabidopsis,in drought stress,the relative water content,photosynthetic rate,leaf stomatal densities,and transpiration rate in transgenic Arabidopsis lines overexpressing GhMAC3 were significantly higher in than those in the wild type,whaereas the stomatal sizes and apertures were smaller that the wild types'.(3)under drought stress,drought related genes such as RD22,RD29A,RD29B,P5CSI,ABI5 were up-regulated but XAB1 was down-regulated in GhMAC3 overexpressing lines.(4)2-DE analysis of GhMAC3 over expressing Arabidopsis thaliana and wild type plants showed 24 differentially expressed protein spots.We preliminarily identified that GhMAC3 signifcantly improved heat and drought resistance of Arabidopsis,analysed molecular and physiological mechanisms of drought resistance conferred by GhMAC3 in this thesis,our results pave the way for further functional analysis and application of this gene.