Following double fertilization, plant endosperm nuclei undergo syncytial divisions, followed by synchronous cellularization. Cellularization is a key event during endosperm development, but our understanding of its regulation is limited to Arabidopsis. In this study we show that OsbZIP76 regulates cellularization in rice (Oryza sativa). Activation of OsbZIP76 coincided with the initiation of cellularization, and its knockdown or knockout mutants exhibited precocious cellularization. Genes involved in endosperm development or starch biosynthesis were prematurely activated in the osbzip76 caryopsis. As a putative transcription factor, OsbZIP76 alone lacked transcriptional activation activity; however, it interacted with the nuclear factor Y (NF‐Y) family transcription factors OsNF‐YB9 and OsNF‐YB1 in yeast and in planta. OsbZIP76 and OsNF‐YB9 were predominantly expressed in the endosperm and the proteins colocalized. Seeds of osnf‐yb1 and osbzip76 mutants showed reduced size and reduced apparent amylose content. The parent‐of‐origin‐dependent expression of OsbZIP76 is variable in different rice accessions. In summary, OsbZIP76 is an endosperm‐expressed imprinted gene that regulates endosperm development in rice.

中文翻译：

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OsbZIP76与OsNF-YBs相互作用并调节水稻（Oryza sativa）中的胚乳细胞化。

双重受精后，植物胚乳核经历合胞分裂，随后同步细胞化。细胞化是胚乳发育过程中的关键事件，但我们对其调节的了解仅限于拟南芥。在这项研究中，我们表明OsbZIP76调节水稻（水稻）的细胞化。OsbZIP76的激活与细胞化的启动相吻合，其敲低或敲除突变体表现出早熟的细胞化。osbzip76中过早激活了涉及胚乳发育或淀粉生物合成的基因颖果。作为推定的转录因子，单独的OsbZIP76缺乏转录激活活性。但是，它在酵母和植物中与核因子Y（NF-Y）家族转录因子OsNF-YB9和OsNF-YB1相互作用。OsbZIP76和OsNF-YB9主要在胚乳中表达，并且蛋白质共定位。osnf-yb1和osbzip76突变体的种子显示尺寸减小和表观直链淀粉含量降低。OsbZIP76的起源于母体的表达在不同水稻品种中是可变的。总之，OsbZIP76是胚乳表达的印迹基因，可调节水稻胚乳的发育。