小麦种子休眠相关因子NACSD的鉴定和功能研究

Seed dormancy is an important quantitative trait related to plant survival and agricultural production with complex molecular mechanisms. Allohexaploid wheat is an important crop in the world. Since its large reference genome, little is known about the molecular mechanisms of seed dormancy compared to model plants. Recently we found that NACSD, a member of the plant specific transcription factor NAC family, was involved in the regulation of seed dormancy by RNA-seq analysis. Furthermore, loss-of-function of AtNACSD caused deep seed dormancy in Arabidopsis, but nothing is reported about NACSD function and roles in seed development so far. Therefore, we make this proposal to further investigate the function of NACSD in the regulation of seed dormancy through combining several approaches such as molecular genetics, transcriptomics, cell biology, physiology and biochemistry. Moreover, we will develop molecular markers based on NACSD sequence variations and serves for molecular marker assisted breeding. The work will greatly increase our understanding on the molecular mechanisms of wheat seed dormancy and help to improve crops in the future.

种子休眠是关乎植物生存和农业生产的重要数量性状，具有复杂的分子调控机制。异源六倍体小麦是世界范围内的重要粮食作物，由于参考基因组庞大，目前对其休眠分子调控机制的解析不如模式植物清晰。项目前期基于转录组数据挖掘到小麦种子特异性表达的休眠候选基因NACSD，通过拟南芥突变体筛选发现AtNACSD缺失可以导致种子休眠加深，生物信息分析显示NACSD为植物特异转录因子NAC家族的成员，目前还没有关于NACSD功能与种子发育相关的报道。以此为基础，我们将结合基因表达模式和遗传转化分析，综合运用组学、生理生化和细胞生物学等技术探究NACSD调控小麦种子休眠的分子机制。同时基于NACSD的自然序列变异，开发分子标记，服务于小麦遗传育种。项目的实施不仅能够解析NACSD参与调控种子休眠的分子机制，还能为遗传育种改良作物提高产量和品质提供理论基础。

种子休眠是关乎植物生存和农业生产的重要数量性状，具有复杂的分子调控机制。异源六倍体小麦是世界范围内的重要粮食作物，由于参考基因组庞大，目前对其休眠分子调控机制的解析不如模式植物清晰。本研究基于转录组数据挖掘到小麦种子特异性表达的休眠候选基因NACSD。拟南芥AtNACSD缺失导致种子休眠加深，将小麦NACSD的CDS序列过表达至拟南芥导致种子休眠减弱，表明NACSD在小麦和模式植物拟南芥中具有保守的功能。AtNACSD与其同源基因AtNACSD1-3双突种子休眠减弱，存在功能冗余。遗传试验结果表明AtNACSD位于RGL2和DOG1的遗传上位，并独立于ANAC60和ANAC25途径调控种子休眠。NACSD定位在细胞核，具有转录因子的典型特征，且在小麦籽粒中特异性高表达。基于NACSD在启动子处的自然序列变异（CA/C-）开发的分子标记能够区分233份自然材料的休眠表型，可有效应用于分子标记辅助育种。与野生型相比，NACSD的Crispr敲除株系（ED109和ED110）表现为休眠加深，纯合过表达株系（OE19和OE21）表现为休眠减弱，说明NACSD负向调控种子休眠。与野生型相比，NACSD对脱落酸（ABA）和赤霉素（GA）更敏感，NACSD可能通过ABA和GA途径调控种子休眠。此外，基因表达网络显示NACSD与休眠相关基因MFT、ABI5、HY5和ELF3等共表达。研究结果不仅为解析NACSD参与调控种子休眠的分子机制提供理论基础，且为分子遗传育种改良作物提高产量和品质提供应用价值。