水稻胚乳特异表达转录因子OsNF-YB9调控胚乳发育的分子机制研究

Endosperm development and grain filling is critical for grain yield and quality of rice. Nuclear Factor Y (NF-Y) transcription factor (TF), composed of NF-YA, NF-YB, and NF-YC subunits, play important roles in diverse biological processes, including endosperm development. However, most of the work focusing on specific members of the NF-Y subunit family, the NF-Y by forming protein complex is poorly studied in higher plants. In this study, transcriptional profiling and phylogenetic analyses were performed to identity a group of endosperm-specific NF-Y genes, including NF-YA8、NF-YB1/9 and NF-YC8/9/10/11/12. The results of yeast two hybrid showed OsNF-YB9 was able to physically interact with other two endosperm-specific expressed NF-Y subfamilies, NF-YA（NF-YA8）and NF-YC (NF-YC8/9//10/11/12). The specific expression patterns of OsNF-YB9 indicated a key role of OsNF-YB9 in maintaining the endosperm development, and the interaction between OsNF-YB9 and other NF-Y members give us a vital clue NF-Y might function as a complex in endosperm development of rice. Building on the preliminary results, we will focuses on the fine analysis the molecular mechanism of OsNF-YB9 in endosperm development, by employing genetics, molecular techniques and bioinformatics to detect the biological function，the relationship with other endosperm-specific NF-Y members and relevant downstream factors. The results could potentially contribute to improving crop yield and provide informative insights into the molecular functional mechanisms of the NF-Y factor.

水稻胚乳发育和充实决定着稻米的产量和品质。NF-Y转录因子由NF-YA、NF-YB和NF-YC三个亚基组成，在诸多生命活动中起重要作用。目前，植物NF-Y的研究还主要停留在对其家族单个基因的功能研究上，整体层面上NF-Y复合体的研究尚欠缺。我们前期分析发现一组水稻胚乳特异表达的NF-Y，包括NF-YA8、NF-YB1/9以及NF-YC8/9/10/11/12。其中，OsNF-YB9可以和其他胚乳特异表达的NF-YA以及NF-YC亚家族成员互作，暗示了他们可能以复合体的形式调控胚乳发育。因此，本项目以OsNF-YB9为研究切入点，利用遗传学，分子与生物化学以及生物信息学揭示OsNF-YB9的生物学功能，与其他NF-Y基因的关系及下游调控因子，阐明其调控胚乳发育的分子机制。该项目将不仅使我们更加深入的了解水稻胚乳发育的分子机理，为作物育种提供理论依据，同时更深刻的认识植物NF-Y的作用机制。

水稻胚乳是人类粮食的主要来源。NF-Y转录因子由NF-YA、NF-YB和NF-YC三个亚基组成，在包括籽粒发育的诸多生命活动中起重要作用。本项目研究发现一组水稻胚乳特异表达的NF-Ys，包括NF-YA8、NF-YB1/9以及NF-YC8/9/11/12。我们利用酵母双杂交系统的分析这些亚基间的相互作用，发现OsNF-YB9可以和其他胚乳特异表达的NF-YA以及NF-YC亚家族成员互作。除了NF-Ys之间存在相对作用，NF-YBs和NF-YCs还可以和转录因子ERF互作。此外我们重点分析了OsNF-YB9的功能，序列分析和功能互补实验证明OsNF-YB9和OsNF-YB7序列和功能和拟南芥LEC1保守的；但是在水稻中OsNF-YB9和OsNF-YB7由于表达模式的不同，在进化过程中发生的了功能分化。OsNF-YB9主要调控水稻胚乳的发育，而OsNF-YB7则主要参与水稻胚的发育。OsNF-YB7突变后胚胎致死；OsNF-YB9突变后影响水稻籽粒的粒型和灌浆，具体表现在：与野生型相比，osnf-yb9籽粒显著变长，变细和变薄、并且垩白粒率和垩白度明显上升。酵母双杂，BiFC和GST pull-down等实验证实OsNF-YB9可以和SPK互作，共同调控水稻籽粒发育。此外，OsNF-YB9的异位表达会导致水稻营养生长和生殖生长的异常。综上所述，水稻NF-YB9对籽粒的发育是必须的。该项目研究结果不仅使我们更加深入的了解水稻胚乳发育的分子机理，为作物育种提供理论依据，同时为我们更深刻的认识植物NF-Y的作用机制提供支持。