基于mGWAS解析bHLH26调控水稻茉莉酸代谢途径的遗传和分子机理

Jasmonates is a kind of important plant hormone, which plays an important role in regulating development and environmental adaptation. Jasmonic acid was derived from lipid metabolism, which can be further modified to produce various derivatives. Studies in several species revealed that jasmonates’ accumulation displayed spatial and temporal distribution as well as effected by various external stimuli, suggesting that the metabolic pathways of jasmonic acid may be regulated by complex transcriptional regulation. However, the key transcription factors for the response to external stimuli of jasmonates have not been reported. Herein, rice core germplasm is used for genome-wide association analysis with different methods to identify candidate genes regulating jasmonic acid metabolic pathways. Biochemical and genetic studies will be performed to illuciate the effect of natural variation of candidate genes on jasmonates accumulation. Our study will decipher the transcriptional regulation mechanism of jasmonic acid pathway. Through the response of the transgenic plants to the stress condition, the effect of the mediated jasmonic acid metabolic pathway on the environmental adaptation will be analyzed. Based on the abovementioned studies, the followed deep mining of genetic resources will provide a theoretical basis for the genetic improvement of rice resistance.

茉莉素是一类重要的植物激素，在调节植物生长发育和环境适应等方面发挥重要作用。植物脂肪酸代谢生成茉莉酸，进一步修饰可以生成多种衍生物，茉莉酸及其衍生物统称茉莉素。多个物种的研究表明，茉莉素含量存在显著的时空差异，并受到多种外界刺激的影响，这提示茉莉酸途径可能受到复杂的转录调控。然而，植物茉莉素响应外界刺激的关键转录因子尚无报道。本申请以水稻核心种质为材料，以茉莉酸途径物质的含量及两两代谢物含量比值为靶性状，应用多种算法进行全基因组关联分析，预测可能影响茉莉酸代谢途径的候选基因，从中筛选重要转录因子，并从遗传学和分子生物学角度研究候选基因自然变异对茉莉素含量的影响，从而解析水稻茉莉酸代谢途径的转录调控机理。通过转基因后代对胁迫条件的响应揭示该转录调控途径在茉莉素环境应答中的作用及其介导的茉莉酸代谢途径在环境适应中的意义。基于以上研究，深入挖掘遗传资源，为水稻抗逆性状的遗传改良提供理论基础。

植物脂肪酸代谢生成茉莉酸，进一步修饰可以生成多种衍生物，茉莉酸及其衍生物统称茉莉素，在调节植物生长发育和环境适应等方面发挥重要作用。茉莉素含量存在显著的时空差异，并受到多种外界刺激的影响，这提示茉莉素稳态维持可能受到复杂的转录调控。然而，植物茉莉素稳态维持的转录调控机制尚待深入研究。本项目优化了代谢物多样性的遗传基础研究方法，建立了水稻高效基因编辑载体构建的技术体系。基于上述基础，本课题以水稻叶片茉莉素含量及其比值为靶性状开展了全基因组关联分析，定位到了多个候选基因。进一步，本项目开展了转基因实验，验证了转录因子bHLH26控制茉莉素含量的功能。转录组测序和DAP-seq联合分析表明，JA-Ile合成的关键基因JAR1可能是bHLH26的直接靶基因。此外，ABA合成的正调控基因bZIP23可能也是bHLH26直接调控的靶点。本项目进一步开展了酵母单杂交、双荧光素酶和微量热泳动实验，证明bHLH26能够直接结合JAR1和bZIP23的启动子，并激活后者表达。本研究还发现，bHLH26参与水稻低温适应性。上述成果完善了对水稻茉莉素合成调控机制的认识，揭示了bHLH26的多重生物学功能，为水稻遗传改良奠定了理论基础。