籼稻和粳稻全基因组6mA修饰鉴定和功能分析

DNA methylation is involved in the control of rice developmental processes and environment adaption, which is a main epigenetic modification to assist rice breeding for specific agronomical traits. DNA methylation on N6-adenine (6mA) has recently been found as a potentially new epigenetic mark in several unicellular and multicellular eukaryotes. However, the distribution patterns and potential functions of 6mA in land plants, especially in crop remain completely unknown. Firstly, we investigated if 6mA presence and level variation among indica and japonica cultivars, and revealed that 6mA levels in rice seedlings are ranging obviously. We further investigated whether 6mA is dynamic in response to stresses, by treated the Nippobare and 93-11 seedlings in cold and heat stress. We found that 6mA is more sensitive to the environmental changes compared to 5mC, which is relatively stable in the treatments. 6mA level changes are significant different between 93-11 and Nip, specificity, 6mA level decreased significant more in Nip in cold treatment, and 6mA level increased significant more in 93-11 in heat shock. Based on the above results, this project will further uncover the global profiling of 6mA at single-nucleotide resolution in indica and japonica rice, identify key genes in regulation of 6mA methylation, and study molecular mechanism of 6mA modification related with developmental process and stress response. This project may contribute to provide theoretical basis, gene resources and breeding materials for rice breeding and production.

DNA甲基化在水稻发育、环境适应性等多个生物学过程中起着重要的调控作用，是表观遗传变异应用于育种和生产的主要修饰方式之一。DNA腺嘌呤甲基化（N6-adenine，6mA）是新的、关键的表观遗传标记，在调控基因表达、发育过程中起着关键作用，但其位点分布及功能在高等植物尤其在作物中尚不清楚。我们发现6mA在籼稻和粳稻品种间广泛存在，含量差异明显；并且籼稻9311和粳稻日本晴的6mA含量在温度胁迫时存在显著变化和差异，显示6mA可能是水稻响应温度变化的重要表观标记；同时鉴定了可能的6mA修饰蛋白，具有结合6mA位点的功能。因而，本项目希望通过研究绘制籼稻和粳稻的全基因组6mA单碱基图谱，比较分布模式和参与调控网络的差异，鉴定关键基因，解析响应温度变化和提高抗逆性的分子机制，为利用籼稻和粳稻农艺性状差别的育种和生产提供理论基础、基因资源和育种材料。

DNA甲基化在水稻发育、环境适应性等多个生物学过程中起着重要的调控作用，是表观遗传变异应用于育种和生产的主要修饰方式之一。腺嘌呤甲基化（N6-methyldeoxyadenosine；6mA）是新鉴定的表观遗传标记，在调控基因表达、发育过程中起着关键作用，但其位点分布及功能在高等植物尤其在作物中尚不清楚。本项目以籼稻和粳稻的代表性品种为材料，发现不同水稻品种的基因组上广泛存在DNA 6mA修饰。随后利用SMRT-seq绘制籼稻93-11和粳稻Nip的DNA 6mA全基因组单碱基分辨率甲基化修饰图谱，鉴定了水稻中参与调控DNA 6mA修饰的重要基因DDM1、OsOSB1和OsOSB2，以及DNA 6mA甲基化修饰复合体OsOSB2-DRW1。在此基础上进一步创制了相关的突变体材料并对其关键农艺性状和对极端温度的应答模式进行研究，发现DDM1介导DNA 6mA修饰调控水稻株高和小穗发育相关基因的表达；OsOSB1介导DNA 6mA调控水稻节间伸长和小穗发育；OsOSB2介导DNA 6mA调控水稻节间伸长和分蘖数量。同时筛选出具有增产表型的水稻新材料OsOSB2-OE和耐高温的ososb2突变体材料。此外，项目组还构建了植物DNA 6mA智能预测在线工具SMEP和数据库eRice，能够实现DNA 6mA修饰位点的精准预测，以推进作物的智能设计育种。综上所述，本项目解析了DNA 6mA调控籼稻和粳稻生长发育和环境适应性差异的分子机制，为利用籼稻和粳稻的农艺性状差别的育种和生产提供理论基础、基因资源和育种亲本。