A SnRK1-ZmRFWD3-Opaque2 Signaling Axis Regulates Diurnal Nitrogen Accumulation in Maize Seeds[OPEN]
A SnRK1-ZmRFWD3-Opaque2 Signaling Axis Regulates Diurnal Nitrogen Accumulation in Maize Seeds[OPEN]
复制标题
SnRK1-ZmRFWD3-Opaque2 信号轴调节玉米种子中的昼夜氮积累
DOI：
10.1105/tpc.20.00352
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发表时间：
2020-09-01
期刊：
影响因子：
11.6
通讯作者：
Song, Rentao
中科院分区：
文献类型：
--
作者：
Li, Chaobin;Qi, Weiwei;Song, Rentao
玉米醇溶蛋白（Zein）是玉米（Zea mays）种子中主要的贮藏蛋白，Opaque 2（O2）是玉米醇溶蛋白编码基因的主要转录因子。O2的活性是如何被调节并对外部信号做出反应的，这在很大程度上是未知的。在这里，我们表明，E3泛素ligaseZmRFWD 3与O2相互作用，并积极调节其活性，通过增强其核定位。O2的泛素化增强了其与玉米Importin-1的α-亚基玉米importin-1的相互作用，从而增强其核定位能力。我们进一步表明ZmRFWD 3可以被Suc响应蛋白激酶ZmSnRK 1磷酸化，从而导致其降解。我们证明O2的活性通过ZmSnRK 1-ZmRFWD 3-O2信号轴响应Suc水平。有趣的是，我们发现Suc水平，以及ZmRFWD 3水平和O2的细胞核分布，在发育胚乳中表现出昼夜模式，导致O2-regulatedzeingenes的昼夜转录。ZmRFWD 3功能的丧失破坏了O2细胞核分布和玉米醇溶蛋白生物合成的昼夜模式，从而改变了成熟种子中的C/N比。因此，我们确定了一个SnRK 1-ZmRFWD 3-O2信号转导轴源到库的信号和协调C和N同化在发展中的玉米种子。
Nitrogen assimilation in developing maize seeds is regulated by the SnRK1-ZmRFWD3-O2 signaling axis, which is responsive to diurnal sucrose concentrations.Zeins are the predominant storage proteins in maize (Zea mays) seeds, while Opaque2 (O2) is a master transcription factor for zein-encoding genes. How the activity of O2 is regulated and responds to external signals is yet largely unknown. Here, we show that the E3 ubiquitin ligaseZmRFWD3 interacts with O2 and positively regulates its activity by enhancing its nuclear localization. Ubiquitination of O2 enhances its interaction with maize importin1, the alpha-subunit of Importin-1 in maize, thus enhancing its nuclear localization ability. We further show thatZmRFWD3 can be phosphorylated by a Suc-responsive protein kinase,ZmSnRK1, which leads to its degradation. We demonstrated that the activity of O2 responds to Suc levels through theZmSnRK1-ZmRFWD3-O2 signaling axis. Intriguingly, we found that Suc levels, as well asZmRFWD3 levels and the cytonuclear distribution of O2, exhibit diurnal patterns in developing endosperm, leading to the diurnal transcription of O2-regulatedzeingenes. Loss of function inZmRFWD3 disrupts the diurnal patterns of O2 cytonuclear distribution and zein biosynthesis, and consequently changes the C/N ratio in mature seeds. We therefore identify a SnRK1-ZmRFWD3-O2 signaling axis that transduces source-to-sink signals and coordinates C and N assimilation in developing maize seeds.