小麦12-羰-植物二烯酸还原酶基因在植物耐盐中的作用机制研究

12-oxo-phytodienoic acid (OPDA) consists of four isomers, cis-(+)-, cis-(-)-, trans-(+)- and trans-(-)-OPDA, and cis-(+)-isomer can be in vivo converted into trans-(+)-OPDA. OPDA serves as not only a signaling molecule but also an oxidant, and is a substrate of OPDA reductase (OPR). OPRs are classified into subgroups OPRI and OPRII, of which OPRIIs catalyze cis-(+)-OPDA to finally form JA, while the function of OPRIs is not clear so far. OPRI genes can be induced by various biotic and abiotic stresses, and OPRIs have in vitro activity to trans-(+)- and cis-(-)-isomers, suggesting they could play important roles in stress response via modulating different OPDA isomers, and a putative association may be present between OPRI and OPRII catalyzing branches. We isolated two salt-induced OPRI genes, TaOPR1 and TaOPR2, from a wheat introgression cultivar SR3 with high salt tolerance, and found that TaOPR1 overexpression promoted salt tolerance and antioxidant ability in both wheat and Arabidopsis. In this proposal, we would analyze the response profiles of TaOPR1 and TaOPR2 to various abiotic stresses, measure in vitro and in vivo catalyzing activity of TaOPR1 and TaOPR2 and ascertain their substrates, detect TaOPR1- and TaOPR2-regulating genes and their exerting effects on JA and ABA pathways, isolate key factors controlling the expression of TaOPR1 and TaOPR2, so as to primarily elucidate the underlying mechanism of OPRI genes in salt tolerance and antioxidation of plants.

12-羰-植物二烯酸（OPDA）有四种异构体，在体内cis-(+)可转换为trans-(+)异构体。OPDA是OPDA还原酶（OPR）的底物，后者分为OPRI和OPRII两个亚家族，OPRII催化cis-(+)异构体最终合成JA，而OPRI功能还不清楚。OPRI基因能被多种胁迫诱导，OPRI体外能催化trans-(+)和cis-(-)异构体，暗示OPRI可能通过控制不同OPDA异构体在植物胁迫应答中发挥重要作用。我们从小麦渐渗系耐盐新品种SR3中克隆了盐响应的OPRI基因TaOPR1和TaOPR2，其中TaOPR1过表达能提高小麦和拟南芥的耐盐/抗氧化能力。本项目拟系统分析TaOPR1/2的胁迫应答特征，测定其编码蛋白的催化活性，确定其催化底物，分离调控TaOPR1/2及受其调控的关键基因，分析其与JA和ABA途径的关系，初步阐明OPRI基因在植物耐盐/抗氧化中的作用机制。

12-羰-植物二烯酸（OPDA）有四种异构体，在体内cis-(+)可转换为trans-(+)异构体。OPDA 是OPDA 还原酶（OPR）的底物，后者分为OPRI 和OPRII 两个亚家族，OPRII 催化cis-(+)异构体最终合成JA，而OPRI 功能还不清楚。本项目首次发现小麦OPRI亚家族基因TaOPR1能提高植物的耐盐和抗氧化能力，利用遗传学分析验证了OPRI分支通过ABA通路增强MYC2的表达提高耐盐能力。另一方面，通过催化JA合成分支的小麦丙二烯氧化物环化酶基因TaAOC1的功能分析，发现JA合成分支通过促进JA信号通路增强MYC2的表达提高耐盐能力。TaOPR1和TaAOC1研究结果表明，OPR I分支和JA分支分别通过不同机制提高MYC2的表达来提高耐盐能力。此外，我们发现，OPR I分支降低抗病性，而JA分支则提高抗病性。综上，我们发现OPR I分支和JA分支在不同逆境响应中发挥复杂而多样化的作用，这些结果为进一步阐明植物耐逆机制提供了重要线索，并为小麦（作物）分子育种提供了重要元件。