油菜素内酯和生物钟协调控制植物生长和免疫抗病平衡的分子机制

The trade-off between growth and immunity is crucial for high yield and disease-resistance of crops. This trade-off is believed to require complex interactions between plant hormones, circadian rhythm and environmental signals. However, the mechanism underlying growth-immunity balance has remained elusive. The bHLH transcription factor HBI1, as a key component of brassinosteroid (BR) signaling transduction, has been reported to play an important role in regulating the dynamic balance of plant growth and immunity. Recently our research results showed that HBI1 interacted with the key regulator of circadian clock, HIC1 to regulate the gene expression, suggesting HBI1 and HIC1 maybe integrate BR and circadian rhythm to control plant growth and immunity. Here we want to analysis the HIC1 binding and regulated genes in Arabidopsis genome, construct the HBI1- and HIC1-regulated gene network, and functional study of HBI1 and HIC1 in BR signal transduction, circadian oscillation, plant growth and immunity. These results will help us to clarify the mechanism in which BR and circadian cross talk to regulate the trade-off between growth and immunity, and provide some new tools for breeding disease-resistance high-yield crops.

植物生长和免疫的动态平衡是植物增产抗病的关键，如何保证植物在抗病的同时还能增产是国际植物学研究的前沿热点领域。植物生长和免疫抗病受到植物激素和生物钟系统的协同调控，但其分子机制目前还不是很清楚。我们前期的研究工作显示植物甾醇类激素油菜素内酯（BR）通过其下游关键的bHLH转录因子HBI1，与病原菌分泌产生的微生物相关分子（PAMPs）相拮抗，协调控制植物生长和免疫抗病的平衡。我们最新的研究结果显示HBI1能与生物钟关键调控蛋白HIC1形成复合体共同调控基因表达。因此在本项目中我们将通过研究HBI1与HIC1的互作机理，及HBI1和HIC1调控的基因网络来探讨HBI1和HIC1在BR信号转导、生物钟调控、植物生长和免疫抗病中的功能，来逐步阐明植物在正确的时间准确调控植物生长和免疫抗病平衡的分子机制，为我们下一步高产抗病育种提供扎实的理论基础和技术保障。

植物生长和免疫抗病的动态平衡是植物高产抗病的关键，如何保证植物在抗病的同时还能高产是国际植物学研究的重点。植物生长和免疫抗病受到植物激素和生物钟的协同调控，但其分子机制目前还不是很清楚。本课题的研究显示植物激素油菜素内酯信号转导的关键转录因子HBI1能直接结合并抑制水杨酸合成基因SID2的表达，使得植物体内水杨酸的降低，从而更易于感病。植物生物钟的重要调控元件HIC1能与HBI1相互作用，并抑制HBI1与SID2启动子结合，使得植物体内水杨酸特异的在暗中积累。HIC1缺失导致植物的细胞伸长，并表现为对生长素、油菜素内酯、赤霉素超敏感，而对光不敏感。生长素、赤霉素、油菜素内脂和黑暗能抑制HIC1的表达，但促进HBI1的活性。而病原菌信号则能促进HIC1的转录而抑制HBI1的表达。植物生长信号和病原菌信号通过调控HBI1和HIC1的活性，调控了植物体内水杨酸的含量，进而调控了植物生长和免疫抗病的平衡。我们这项研究阐明了植物生长激素和免疫抗病激素水杨酸相互作用调控植物生长和免疫抗病平衡调控的分子机理，为我们下一步更科学、合理、有效的利用植物激素来调控作物生长和增强抗病性，并为培育高产抗病的作物品种提供了扎实的理论基础和技术支撑。