National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430070, China.
State Key Laboratory of Cotton Biology, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, 455000, China.
Plant J. 2020 Jul;103(2):532-546. doi: 10.1111/tpj.14748. Epub 2020 Apr 14.
Seed germination is a complex process involving various physical and biochemical cues, determined by exogenous and endogenous factors. Here, we identified a gene, OsMFT2, that negatively regulates seed germination in rice. OsMFT2 knock-out lines exhibited pre-harvest sprouting, whereas OsMFT2 overexpression lines showed delayed germination. RNA expression profiling showed that OsMFT2 was specifically expressed in seeds. Subcellular localization indicated that OsMFT2 was a nuclear protein. Exogenous abscisic acid (ABA) treatment of imbibed seeds and seedlings indicated that OsMFT2 altered ABA sensitivity during seed germination and post-germination growth. In vivo and in vitro assays showed that three bZIP transcription factors, OsbZIP23, OsbZIP66 and OsbZIP72, interacted with OsMFT2. OsbZIP23/66/72 bound to the promoter of Rab16A, a typical gene containing the ABA-responsive element, and OsMFT2 enhanced the binding to the Rab16A promoter. Moreover, several ABA-responsive genes were differentially expressed in the imbibed seeds of OsMFT2 transgenic lines and the wild type. The performance of the transgenic plants demonstrated that overexpressing OsbZIP23 rescued the pre-harvest sprouting phenotype and the decrease in ABA-signaling genes expression caused by OsMFT2 knock-out. All of these results demonstrate that OsMFT2 positively regulates ABA-responsive genes through interacting with OsbZIP23/66/72 and functions in seed germination.
种子萌发是一个复杂的过程，涉及各种物理和生化线索，由外源和内源因素决定。在这里，我们鉴定了一个基因 OsMFT2，它负调控水稻种子的萌发。OsMFT2 敲除系表现出提前抽穗，而 OsMFT2 过表达系表现出延迟萌发。RNA 表达谱分析表明，OsMFT2 特异性表达于种子中。亚细胞定位表明 OsMFT2 是一种核蛋白。外源脱落酸（ABA）处理吸胀种子和幼苗表明，OsMFT2 在种子萌发和萌发后生长过程中改变了 ABA 敏感性。体内和体外测定表明，三个 bZIP 转录因子 OsbZIP23、OsbZIP66 和 OsbZIP72 与 OsMFT2 相互作用。OsbZIP23/66/72 结合到 Rab16A 的启动子上，Rab16A 是一种含有 ABA 反应元件的典型基因，而 OsMFT2 增强了与 Rab16A 启动子的结合。此外，几个 ABA 响应基因在 OsMFT2 转基因系和野生型种子的吸胀种子中差异表达。转基因植物的表现表明，过表达 OsbZIP23 挽救了 OsMFT2 敲除导致的提前抽穗表型和 ABA 信号基因表达的降低。所有这些结果表明，OsMFT2 通过与 OsbZIP23/66/72 相互作用正向调控 ABA 响应基因，并在种子萌发中发挥作用。
