The O2-ZmGRAS11 transcriptional regulatory network orchestrates the coordination of endosperm cell expansion and grain filling in maize
The O2-ZmGRAS11 transcriptional regulatory network orchestrates the coordination of endosperm cell expansion and grain filling in maize
复制标题
O2-ZmGRAS11 转录调控网络协调协调玉米胚乳细胞扩张和籽粒灌浆。
DOI：
10.1016/j.molp.2021.11.013
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发表时间：
2022-03-07
期刊：
影响因子：
27.5
通讯作者：
Wu, Yongrui
中科院分区：
文献类型：
--
作者：
Ji, Chen;Xu, Lina;Wu, Yongrui
玉米胚乳的充实与细胞的膨大是相互协调的，二者的相互作用机制尚不清楚。淀粉胚乳细胞基本上不含可见的细胞扩展液泡。在籽粒灌浆过程中，有效合成的存储化合物导致细胞质减少，从而降低细胞膨压。虽然生物活性赤霉素（GAs）是细胞扩增所必需的，但它们在此阶段的积累水平很低。在这项研究中，我们确定了胚乳特异性的GRAS结构域的蛋白质（ZmGRAS 11），缺乏DELLA结构域，并促进填充胚乳细胞扩张。zmgras 11功能丧失突变体表现出正常的籽粒灌浆，但延迟细胞扩张，从而导致籽粒大小和重量减少。ZmGRAS 11的过表达导致更大的胚乳细胞，因此增加了籽粒大小和重量。与此一致，ZmGRAS 11正调控ZmEXPB 12的表达，这是细胞扩张所必需的，在胚乳灌浆阶段。此外，我们发现，Opaque 2（O2），一个中央转录因子调节胚乳充实，可以直接结合到ZmGRAS 11的启动子，并激活其表达。两者合计，这些结果表明，胚乳细胞扩张与胚乳填充，这是精心策划的O2-ZmGRAS 11为中心的转录调控网络。我们的研究结果也为通过提高胚乳细胞的贮藏能力来提高玉米产量提供了潜在的目标。
Maize (Zea mays) endosperm filling is coordinated with cell expansion to enlarge the grain size, but the mechanism coupling the two processes is poorly understood. Starchy endosperm cells basically contain no visible vacuoles for cell expansion. During grain filling, efficient synthesis of storage compounds leads to reduced cytoplasm and thus lowered cell turgor pressure. Although bioactive gibberellins (GAs) are essential for cell expansion, they accumulate at a low level at this stage. In this study, we identified an endosperm-specific GRAS domain-containing protein (ZmGRAS11) that lacks the DELLA domain and promotes cell expansion in the filling endosperm. The zmgras11 loss-of-function mutants showed normal grain filling but delayed cell expansion, thereby resulting in reduced kernel size and weight. Overexpression of ZmGRAS11 led to larger endosperm cells and therefore increased kernel size and weight. Consistent with this, ZmGRAS11 positively regulates the expression of ZmEXPB12, which is essential for cell expansion, at the endosperm filling stage. Moreover, we found that Opaque2 (O2), a central transcription factor that regulates endosperm filling, could directly bind to the promoter of ZmGRAS11 and activate its expression. Taken together, these results suggest that endosperm cell expansion is coupled with endosperm filling, which is orchestrated by the O2-ZmGRAS11-centered transcriptional regulatory network. Our findings also provide potential targets for maize yield improvement by increasing the storage capacity of endosperm cells.