Homodimerization of Ehd1 Is Required to Induce Flowering in Rice
Homodimerization of Ehd1 Is Required to Induce Flowering in Rice
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DOI：
10.1104/pp.15.01723
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发表时间：
2016-04-01
期刊：
影响因子：
7.4
通讯作者：
An, Gynheung
中科院分区：
文献类型：
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作者：
Cho, Lae-Hyeon;Yoon, Jinmi;An, Gynheung
在植物中，开花时间受到各种环境因素的精心控制。最终，成花原如FLOWERLOCUS T（FT）或FT样分子诱导开花。在水稻（Oryza sativa）中，早抽穗期1（Ehd 1）是成花素基因表达的主要诱导因子。虽然Ehd 1与细胞分裂素信号通路中的B型反应调节因子（RR）家族高度同源，但其确切的分子机制尚不清楚。在这项研究中，我们表明，C-末端部分的蛋白质含有GARP DNA结合（G）域可以促进开花时，过表达。我们还观察到，Ehd 1的N-末端部分，携带接收器（R）域，延迟开花抑制内源Ehd 1活性。Ehd 1蛋白通过R和G之间的16个氨基酸区域形成同源体。从定点突变分析，我们证明，在R结构域内的Asp-63残基的磷酸化诱导Ehd 1，这是至关重要的Ehd 1活性的同质化。A型RR，OsRR 1，与Ehd 1物理相互作用形成异二聚体。此外，OsRR 1过表达植物表现出晚开花表型。基于这些观察结果，我们得出结论，OsRR 1通过结合形成无活性复合物来抑制Ehd 1活性。
In plants, flowering time is elaborately controlled by various environment factors. Ultimately, florigens such as FLOWERING LOCUS T (FT) or FT-like molecules induce flowering. In rice (Oryza sativa), Early heading date 1 (Ehd1) is a major inducer of florigen gene expression. Although Ehd1 is highly homologous to the type-B response regulator (RR) family in the cytokinin signaling pathway, its precise molecular mechanism is not well understood. In this study, we showed that the C-terminal portion of the protein containing the GARP DNA-binding (G) domain can promote flowering when overexpressed. We also observed that the N-terminal portion of Ehd1, carrying the receiver (R) domain, delays flowering by inhibiting endogenous Ehd1 activity. Ehd1 protein forms a homomer via a 16-amino acid region in the inter domain between R and G. From the site-directed mutagenesis analyses, we demonstrated that phosphorylation of the Asp-63 residue within the R domain induces the homomerization of Ehd1, which is crucial for Ehd1 activity. A type-A RR, OsRR1, physically interacts with Ehd1 to form a heterodimer. In addition, OsRR1-overexpressing plants show a late-flowering phenotype. Based on these observations, we conclude that OsRR1 inhibits Ehd1 activity by binding to form an inactive complex.