National Key Laboratory of Crop Genetic Improvement and National Centre of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan, Hubei 430070, China; Hubei Hongshan Laboratory, Wuhan, Hubei 430070, China.
National Key Laboratory of Crop Genetic Improvement and National Centre of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan, Hubei 430070, China; Hubei Hongshan Laboratory, Wuhan, Hubei 430070, China.
J Genet Genomics. 2022 May;49(5):414-426. doi: 10.1016/j.jgg.2022.02.002. Epub 2022 Feb 19.
Grain chalkiness, an undesirable trait caused by complex factors, has great negative impacts on the quality and economic value of rice. However, little is known about the regulatory mechanism of grain chalkiness, particularly the effect of endoplasmic reticulum (ER) stress. Here, a genome-wide association study (GWAS) reveals that the transcription factor OsbZIP60 is a vital regulator of rice grain chalkiness. Genetic analysis demonstrates that knockout of OsbZIP60 results in extremely high grain chalkiness and aberrant structure of storage substances. Notably, the expression of unfolded protein response (UPR) genes, such as OsbZIP50, OsBiP1, OsBiP2 and OsBiP3, is up-regulated in the endosperm cells of osbzip60, and overexpression of all these UPR genes causes various degrees of chalkiness. Furthermore, OsbZIP60 is found to activate the expression of key genes related to grain chalkiness, such as GPA3, FSE1, FLO7, Chalk5, OsNF-YB1, and OsPK2, whose expression is significantly suppressed in osbzip60 and overexpression lines of OsbZIP50, OsBiP1, OsBiP2, and OsBiP3. Our study provides novel insights into the function of OsbZIP60 and the role of the UPR pathway in the formation of grain chalkiness in rice.
垩白度是一种由复杂因素引起的不良性状，对稻米的品质和经济价值有很大的负面影响。然而，对于垩白度的调控机制，特别是内质网（ER）应激的作用，知之甚少。在这里，一项全基因组关联研究（GWAS）揭示了转录因子 OsbZIP60 是水稻垩白度的重要调控因子。遗传分析表明，OsbZIP60 的敲除导致极高的垩白度和储存物质的异常结构。值得注意的是，未折叠蛋白反应（UPR）基因，如 OsbZIP50、OsBiP1、OsBiP2 和 OsBiP3 的表达，在 osbzip60 的胚乳细胞中上调，并且所有这些 UPR 基因的过表达导致不同程度的垩白度。此外，发现 OsbZIP60 激活与垩白度相关的关键基因的表达，如 GPA3、FSE1、FLO7、Chalk5、OsNF-YB1 和 OsPK2，其在 osbzip60 和 OsbZIP50、OsBiP1、OsBiP2 和 OsBiP3 的过表达系中表达显著受到抑制。我们的研究为 OsbZIP60 的功能和 UPR 途径在水稻垩白度形成中的作用提供了新的见解。
