National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese academy of Sciences, Shanghai 200032, PR China.
Mol Plant. 2013 Mar;6(2):514-27. doi: 10.1093/mp/sss096. Epub 2012 Sep 12.
Proper flowering time is essential for plant reproduction. Winter annual Arabidopsis thaliana needs vernalization before flowering, during which AtVILs (VIN3 and VRN5, components of PRC2 complex) mediate the H3K27 tri-methylation at the FLC locus (a floral repressor) to repress the FLC expression and hence to induce flowering. However, how VILs (VIL, VERNALIZATION INSENSITIVE 3-LIKE) function in rice is unknown. Here we demonstrated that rice LC2 (OsVIL3) and OsVIL2 (two OsVILs, possible components of PRC2 complex) promote rice flowering. Our results showed that expressions of LC2 and OsVIL2 are induced by SD (short-day) conditions and both lc2 mutant and OsVIL2-RNAi lines display delayed heading date, consistent with the reduced expression levels of Hd1 and Hd3a. Interestingly, LC2 binds to the promoter region of a floral repressor OsLF and represses the OsLF expression via H3K27 tri-methylation modification. In addition, OsLF directly regulates the Hd1 expression through binding to Hd1 promoter. These results first demonstrated that the putative PRC2 in rice is involved in photoperiod flowering regulation, which is different from that of Arabidopsis, and revealed that LC2 binds the promoter region of target gene, presenting a possible mechanism of the recruitment process of PRC2 complex to its target genes. The studies provide informative clues on the epigenetic control of rice flowering.
适当的开花时间对植物繁殖至关重要。冬季一年生拟南芥在开花前需要春化，在此期间，AtVILs（VIN3 和 VRN5，PRC2 复合物的组成部分）介导 FLC 基因座（花抑制物）上的 H3K27 三甲基化，以抑制 FLC 的表达，从而诱导开花。然而，VILs（VIL，VERNALIZATION INSENSITIVE 3-LIKE）在水稻中的功能尚不清楚。在这里，我们证明了水稻 LC2（OsVIL3）和 OsVIL2（两个 OsVILs，可能是 PRC2 复合物的组成部分）促进水稻开花。我们的结果表明，LC2 和 OsVIL2 的表达受 SD（短日照）条件诱导，lc2 突变体和 OsVIL2-RNAi 系表现出开花期延迟，与 Hd1 和 Hd3a 的表达水平降低一致。有趣的是，LC2 结合到花抑制物 OsLF 的启动子区域，并通过 H3K27 三甲基化修饰抑制 OsLF 的表达。此外，OsLF 通过结合 Hd1 启动子直接调节 Hd1 的表达。这些结果首次表明，水稻中假定的 PRC2 参与光周期开花调控，与拟南芥不同，并揭示了 LC2 结合靶基因的启动子区域，为 PRC2 复合物向其靶基因募集的过程提供了一种可能的机制。这些研究为水稻开花的表观遗传调控提供了有价值的线索。
