黄酮醇在盐胁迫应答中的功能及其生物合成的应答调控机制研究

Flavonoids are important secondary metabolites and markedly accumulate to enhance antioxidant capacity of plants under abiotic stress, but the molecular mechanism by which abiotic stress induce their biosynthesis is still unknown. Flavonols are a class of flavonoids with the strongest antioxidant capacity, and serve as signaling molecules in animal cells, while whether they exert regulatory performance in the response to abiotic stress in plants needs to be uncovered. We previously bred a salt-tolerant wheat introgression cultivar SR3 via asymmetric somatic hybridization. In comparison with its parent wheat, SR3 synthesized more flavonols, and accumulated more transcripts of flavonol synthase TaFLS1. TaFLS1 overexpression improved flavonol content and offered salt tolerance, but its RNAi had an opposite effect. In Arabidopsis, flavonol accumulation inhibited the expression of MYC2, an important regulatory factor in abiotic stress signal transduction pathway, and the induction extension of AtFLS1 by salt stress was alleviated in the myc2 mutant, suggesting that MYC2 is a regulatory node of both salt-induced flavonol biosynthesis and feedback regulation of flavonols on their biosynthesis. In this proposal, we will use TaFLS1 overexpression and RNAi lines as well as Arabidopsis genetic materials, to analyze the function and molecular basis of flavonols in salt tolerance, and elucidate the exertion mechanism of MYC2 in salt-induced flavonol synthesis and the feedback regulation of flavonols on their biosynthesis. Our work will provide clues to further understand the role of secondary metabolism in the response to abiotic stress and genetic resource for wheat molecular breeding.

黄酮醇是抗氧化性最强的类黄酮，高盐胁迫可诱导其合成，但诱导的分子机制还不清楚。动物中黄酮醇还能作为信号分子调控胁迫应答，而它能否也调控植物胁迫应答还有待研究。本实验室前期培育了小麦渐渗系耐盐品种山融3号，较亲本小麦在盐胁迫下积累更多的黄酮醇，黄酮醇合成酶TaFLS1上调更显著。TaFLS1过表达提高黄酮醇含量，增强耐盐能力，而其RNAi正好相反；黄酮醇富集抑制胁迫信号通路关键调控因子MYC2表达，而myc2突变体中盐胁迫对黄酮醇合成酶的诱导程度减弱，暗示MYC2是调控盐胁迫诱导黄酮醇合成和黄酮醇反馈调控其合成的关键节点。本项目拟利用TaFLS1过表达和RNAi株系及拟南芥相关遗传材料，分析黄酮醇的耐盐功能和分子基础，验证MYC2在盐胁迫诱导黄酮醇合成及黄酮醇合成反馈调控中的作用机制，为阐明次生代谢在非生物胁迫应答中的功能提供理论依据，并为小麦耐盐分子育种提供遗传资源。

黄酮醇是抗氧化性最强的类黄酮，高盐胁迫下被大量合成，但其在盐胁迫应答中的功能和作用机理以及盐胁迫诱导其合成分子机制还不清楚。本研究以小麦渐渗系耐盐品种山融3号为材料发现，在盐胁迫下较亲本小麦积累更多的黄酮醇，黄酮醇合成酶TaFLS1上调更显著。TaFLS1过表达提高小麦黄酮醇含量，增强耐盐能力，而其RNAi正好相反。外源黄酮醇槲皮素处理能模拟TaFLS1过表达的表型。拟南芥中的平行试验显示，黄酮醇提高耐盐能力的功能在植物中具有保守性。体内黄酮醇富集及外源槲皮素处理能增强抗氧化能力，降低盐胁迫诱导的ROS水平，缓解盐胁迫导致到细胞凋亡，提高盐胁迫下的基因组稳定性。盐胁迫下MYC2突变体中黄酮醇及类黄酮富集程度明显降低，MYC2能结合TaFLS1及其拟南芥同源基因AtFLS1启动子，表明MYC2是盐胁迫诱导黄酮醇（类黄酮）合成中的关键调控因子。鉴定了一个槲皮素互作蛋白FBP，为后续解析槲皮素（黄酮醇）在盐胁迫应答信号通路中的调控作用奠定了基础。多年多点大田试验显示，盐碱地中TaFLS1过表达小麦产量明显提高，而其RNAi小麦产量明显降低，表明TaFLS1是小麦及其他作物分子育种的重要分子元件。