拟南芥MYB42通过BR信号途径负调控细胞伸长的分子机制

Cell elongation is a key factor affecting plant growth and development, disruption of the process in plant will directly lead to a dwarf phenotype. The regulation mechanism of plant cell elongation is complex, which is regulated by many kinds of endogenous hormones and environmental signals. Among them, brassinolide (BRs) is one of the important hormones affecting cell elongation, previous studies had paid more attention to the positive regulatory factors in the BR regulatory pathway, but the negative regulatory factors were relatively few. Our previous studies showed that Arabidopsis MYB42 could affect cell elongation, overexpression of MYB42 in the bri1 mutant (membrane receptor of BR signal transduction pathways) could aggravate its dwarf phenotype, the EMSA experiment showed MYB42 was the direct target of BZR1 and BES1, meanwhile, MYB42 could activate the expression of DOGT1 which was proved as a BR-inactivation gene. Base on the above results, this project using EMSA, gene microarray and ChIP-Seq technologies aims to characterize the biological role of MYB42 in the regulation of cell elongation, identify the downstream target genes of MYB42 involved in cell elongation, reveal the molecular mechanism of MYB42 regulating cell elongation, and finally make the establishment of molecular network of MYB42 negatively regulating cell elongation through BR signaling pathway. These results will lay the theoretical foundation to enrich the understanding of regulation mechanism of plant cell elongation and to cultivate the dwarf crop varieties.

细胞伸长是影响植物生长发育的关键因素，该过程受阻会直接导致植物矮化。植物细胞伸长的调控机制比较复杂，受多种内源激素及环境信号的调控。其中，油菜素内酯（BRs）是影响细胞伸长的重要激素之一，以前的研究更多关注BR调控通路中的正调控因子，对负调控因子的研究相对较少。我们前期研究表明，拟南芥MYB42负调控细胞伸长，过表达后能加剧BR信号受体BRI1突变体bri1-6的矮化表型，EMSA实验证实MYB42是BZR1和BES1的直接靶标，进一步分析发现MYB42能够反馈激活BR合成失活基因DOGT1的表达。在此基础上，本项目拟利用EMSA、基因芯片和ChIP-Seq等技术深入解析MYB42在细胞伸长过程中的功能，鉴定其调控细胞伸长的关键靶标，揭示MYB42调控细胞伸长的分子机制，建立MYB42通过BR途径负调控细胞伸长的分子网络，为丰富人们认识植物细胞伸长调控机制和培育矮化农作物品种奠定理论基础。

细胞伸长是影响植物生长发育的关键因素之一，此过程受阻会直接导致植物发生矮化。植物细胞伸长的调控机制较为复杂，受多种内源激素及环境信号的调控。其中，油菜素内酯（BRs）是影响细胞伸长的重要激素之一，以前的研究更多关注BR调控通路中的正调控因子，对负调控因子的研究相对较少。本项目综合运用生化分析，遗传分析结合组学分析手段，主要得到以下重要结果：（1）拟南芥转录因子MYB42能够负调控细胞伸长；（2）MYB42受油菜素内酯信号的调控，并鉴定出BZR1作为其上游调控因子；（3）MYB42通过调控下游BR信号抑制基因DOGT1的表达形成回路来反馈抑制激素信号的作用。通过本项目的实施，我们深入解析了负调控因子MYB42通过 BR途径参与细胞伸长的转录调控网络，这将为完善BRs调控植物细胞伸长的分子机制奠定基础，故具有一定的理论意义。另一方面，BRs也是农业生产上培育优良矮化农作物品系和提高粮食产量的重要激素，进一步完善BRs调控细胞伸长的分子机制将为遗传改良农作物重要的矮化农艺性状奠定基础，故具有重要的实践意义。