BR诱导下AOX1a基因对芥菜TuMV抗性的调控机理

In the previous research,a poly merase chain reaction(PCR)-based suppression subtractive hybridization technique was used to isolate genes with Turnip mosaic virus (TuMV) resistance，and a mitochondrial alternative oxidase gene (BJAOX1a) was got in Brassica juncea. QRT-PCR results showed that the BJAOX1a highly responsed to TuMV infection and exogenous BR application, and the system resistance in upper leafs of mustard were enhanced by exogenous BR. In order to study the resistance pathway induced by the AOX and the relationship between BR and AOX, the BJAOX1 over-expression and RNAi transformation plants will be constructed. The BR inhibitor Brz and the BR will be applied to study the difference of virus resistance between wild type plants and transformation plants; the expression of BJAOX1a and the resistance induced by BR will be analysed in mustard; changes of ROS content, the phenotype change of mustard resistance, expression of resistant genes and virus coat proteins will also be investigated under different treatments in transgenic plants and wild type plants; The objective of this study is to elaborate the function of AOX in TuMV reistance.

前期研究中，我们利用抑制性差减杂交技术筛选抗性相关基因，得到一个抗芜菁花叶病毒（TuMV）侵染的相关基因芥菜线粒体交替氧化酶基因(BJAOX1a)，QRT-PCR结果表明BJAOX1a高度响应TuMV侵染和外源BR的施用，且外源BR能够有效的提高芥菜系统叶片的抗病性。BR介导的芥菜BJAOX1a抗性途径的机理尚不明确，本项目拟通过构建BJAOX1a基因的过量表达株和RNAi抑制表达株，采用病毒侵染与BR合成抑制剂Brz、BR预处理结合，比较转化材料和野生型植株间的抗病性差异；分析BR对BJAOX1a基因和芥菜抗病性的影响；研究转化植株和野生型植株在不同处理下ROS含量的变化及相关基因的表达，同时结合芥菜抗病反应、抗性基因表达和外壳病毒蛋白的表达情况，阐明TuMV侵染过程中芥菜BJAOX1a介导的抗性途径与BR之间的联系；以期阐述芥菜BJAOX1a的抗病机制。

本项目以9号芥菜为材料，研究了外源BR介导AOX基因的耐盐性的调控机理。盐胁迫条件下，BR能够诱导AOX和保护酶相关基因的表达，提高保护酶的活性，降低植物细胞内活性氧和MDA的含量，进而提高耐盐性。相反的，芥菜抑制或激活AOX均不影响BR合成和信号转导通路DET1、DET2、DWF1、DWF4等基因的相对表达量，因此，芥菜AOX调控的抗性途径可能受BR的生物合成途径的影响。此外，AOX和BR相似可以提高抗氧化酶的活性，降低植物细胞内活性氧和MDA的含量，增强植物的耐盐性。BR可以诱导AOX基因的上调表达，BRZ抑制AOX基因的表达，SHAM并不能完全抑制BR对AOX基因上调表达的影响；AA和BR共同处理会相互促进对AOX基因表达的诱导，且AA对BR的促进作用不显著。以上结论表明：BR可以通过ROS介导AOX的抗性调控路径。