Molecular Mechanism Of Maize Sulfite Oxidase Response To Drought

Sulfite oxidase(ZmSO)is the key enzyme in S metabolic pathway,which oxidizes sulfite to sulfate.In this paper,the molecular mechanism of ZmSO in response to drought was studied using ZmSO-overexpressing Arabidopsis transgenic lines which were constructed previously in our lab.The main results of this thesis are as follows:1.Molecular analysis of ZmSO response to drought stress.Through drought and mannitol treatments on wild type(WT)and ZmSO overexpressed lines ZmSO-15 and ZmSO-20,it was found that drought resistance of over-expressed lines was improved.Arabidopsis thaliana under drought stress with mannitol,the content of Cys in overexpressed lines was significantly higher than WT.ZmSO could promote the accumulation of Cys in plants and then promote the biosynthesis of GSH in plants and improve the drought resistance of plants.2.Molecular analysis of ZmSO response to ABA.Upon exogenous ABA treatment,compared to the WT,both ZmSO-15 and ZmSO-20 showed slower germination and significant root growth inhibition,indicating that ZmSO is more sensitive to ABA.The results suggested that ZmSO might be involved in ABA signal transduction pathway,promote stomatal closure and regulate the expression of ABA and drought stress response genes in plants under drought stress,and enhance drought resistance of plants.ZmSO also involved in regulating the expression of genes related to sulfur assimilation and metabolism in order to improve the drought resistance of plants.3.Analysis of regulatory elements of ZmSO promoter.The ZmSO promoter sequence was obtained by PCR and analyzed by Plant CARE.The plant expression vectors harboring the promoter sequences fused to the GUS coding sequences were constructed and expressed in the Arabidopsis seedlings via the agrobacterium-mediated transformation.GUS staining has shown that ZmSO promoter are expressed at the lesf,flowers and silique of Arabidopsis.ZmSO promoter activity analysis of different deletion mutants.We constructed ZmSO promoters with different deletion fragments and identified the core promoter region of ZmSO promoter at ZmSO transcription start site from-297 bp to-416 bp.By cloning and analyzing the ZmSO promoter sequences from different maize inbred lines,we found that there exists a new allele containing two 14-bp element repeats in the promoter region.Further analysis showed that transcription activity of the allelic variation markedly decreased.