BRS1对植物氧化还原电位调控的机理研究

Brassinosteroids (BRs), a group of phytohormones, mediate various physiological processes in normal plant growth, development and stress responses. Our previous study indicated that overexpression of a serine carboxypeptidase, BRS1 (bri1 SUPPRESSOR 1), can suppress the defective phenotype of bri1-5 (a weak mutant allele of the BR receptor,BRI1). BRS1 therefore was suggested as a regulatory component in BR signaling pathway. Our recent data showed that the trascription of BRS1 is down-regulated by BRs. In addition, we found that BRS1 may also play a role in redox regulation by activating the enzyme activity of an ICDH , which was known to regulate cell redox status and pathogen resistance.These results indicated that BRs may function in plant redox regulation via BRS1.We have four specific objectives in this proposal: 1) How plant redox status is regulated by BRS1? 2) How does BR signaling contribute to plant redox status regulated by BRS1? 3) Inter-relationship among redox status regulated by BRS1, BR signaling and pathogen resistance (or innate immunity).4) Molecular mechanisms of BRS1 in regulating the enzyme activity of ICDH.These studies will contribute to a better understanting of the true molecular mechnisms of BR and BRS1 in regualting plant redox status as well as pathogen resistance.

油菜素内酯（BR）是植物体中一类重要的激素，广泛参与调节植物生长发育与抗逆抗病过程。丝氨酸羧肽酶BRS1(BRI1 SUPPRESSOR 1)的超表达能抑制BR受体突变体bri1-5的矮小表型而被认为是BR信号体系的一员。我们最近的研究表明，BRS1的基因表达受BR信号的负调控。同时，BRS1能将细胞质异柠檬酸脱氢酶（ICDH）活性增强，从而调控细胞内的氧化还原平衡。这些结果表明BR可能通过BRS1调控植物的氧化还原平衡。本申请书包含4个研究目标:1）BRS1对植物氧化还原状态的调控；2）BR信号对BRS1调控的氧化还原状态的影响；3）BRS1调控的氧化还原状态、BR信号和植物抗病力之间的相互关系；4）BRS1调控ICDH酶活的分子机理。这些研究将有助于更好的理解BR与BRS1调控植物氧化还原状态及抗病体系中的作用机制。

该项目原计划对BRS1调控的植物氧化还原状态开展研究，从而解析油菜素内酯（BR）调控的植物氧化还原系统。在获得国家基金委面上项目的支持后，按照预定计划开展研究。进展较为顺利，于2017年发表BRS1调控植物侧根发育的研究论文。此外，根据研究过程中不断更新的结果，调整了部分研究方向，也取得了较好的进展。.我们研究表明BRS1能被BR诱导，在侧根原基邻近的内皮层细胞中表达，作为分泌蛋白进入细胞间隙，聚集在侧根原基的顶端与表面，加快侧根原基突破表皮的速度。在BRS1调控氧化还原状态方面，我们发现BRS1能增加细胞内氧化压力，诱导细胞内氧化还原蛋白的响应。进一步的研究表明BRS1，作为BR调控的基因，其所调控的胁迫响应与先前报道的BR调控领域具有明显差异，主要集中在非生物胁迫响应等方面，尤其是植物应对冷胁迫。RNA-seq的结果表明，超表达BRS1能使冷胁迫信号核心基因CBF1、CBF2和CBF3上调5-10倍，同时诱导了大量冷响应基因的全面表达。通过本项目的研究，进一步阐明了BR信号和BRS1在植物发育与非生物胁迫调控中的重要功能。