Xu Jing-Jing, Zhang Xiao-Fan, Xue Hong-Wei
National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, 200032 Shanghai, China.
National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, 200032 Shanghai, China
J Exp Bot. 2016 Dec;67(22):6399-6411. doi: 10.1093/jxb/erw409. Epub 2016 Nov 1.
Grain yield and quality of rice mainly depend on grain filling and endosperm development. Here we report that a rice NUCLEAR FACTOR Y (NF-Y) transcription factor, OsNF-YB1, is specifically expressed in the aleurone layer of developing endosperm and regulates grain filling and endosperm development. Knockdown of OsNF-YB1 expression by RNAi significantly retarded grain filling, leading to small grains with chalky endosperm as well as altered starch quality. Whereas OsNF-YB1 shows subcellular localization in both the cytosol and the nucleus in roots, it was specifically targeted to the nucleus of aleurone layer cells, which was facilitated by interacting with OsNF-YC proteins preferentially expressed in the aleurone layer. RNA sequencing analysis revealed that genes related to membrane transport and ATP biosynthesis were enriched in the down-regulated category in OsNF-YB1 RNAi plants, which is consistent with the crucial role of OsNF-YB1 in rice grain filling and endosperm development. Identification of the genome-wide targets of OsNF-YB1 by ChIP sequencing showed that OsNF-YB1 directly regulates genes involved in the transport of nutrients such as sugar and amino acids. Interestingly, different from the binding sites reported for other NF-Y complexes, the GCC box, the binding motif of ERF transcription factors, was enriched in the binding peaks of OsNF-YB1. Indeed, further analyses confirmed the interaction of OsERF#115 with OsNF-YB1, and OsERF#115 directly binds to the GCC box. It is proposed that OsNF-YB1 specifically regulate the transcription of downstream genes during rice endosperm development by forming protein complexes consisting of OsNF-YB1, OsNF-YC and ERF, providing informative insights into the molecular functional mechanisms of the NF-Y factor.
水稻的产量和品质主要取决于籽粒灌浆和胚乳发育。在此，我们报道了一种水稻核因子Y（NF-Y）转录因子OsNF-YB1，它在发育中的胚乳糊粉层中特异性表达，并调控籽粒灌浆和胚乳发育。通过RNA干扰敲低OsNF-YB1的表达会显著延缓籽粒灌浆，导致籽粒变小，胚乳出现垩白，同时淀粉品质也发生改变。虽然OsNF-YB1在根细胞的细胞质和细胞核中均有亚细胞定位，但它特异性定位于糊粉层细胞的细胞核，这是通过与在糊粉层中优先表达的OsNF-YC蛋白相互作用实现的。RNA测序分析表明，与膜转运和ATP生物合成相关的基因在OsNF-YB1 RNA干扰植株的下调类别中富集，这与OsNF-YB1在水稻籽粒灌浆和胚乳发育中的关键作用一致。通过染色质免疫沉淀测序鉴定OsNF-YB1的全基因组靶点，结果显示OsNF-YB1直接调控参与糖和氨基酸等营养物质转运的基因。有趣的是，与其他NF-Y复合物报道的结合位点不同，ERF转录因子的结合基序GCC盒在OsNF-YB1的结合峰中富集。事实上，进一步分析证实了OsERF#115与OsNF-YB1的相互作用，且OsERF#115直接结合GCC盒。研究表明，OsNF-YB1通过形成由OsNF-YB1、OsNF-YC和ERF组成的蛋白质复合物，在水稻胚乳发育过程中特异性调控下游基因的转录，为NF-Y因子的分子功能机制提供了有价值的见解。
