Crop Biotech Institute, Kyung Hee University, Yongin, 446-701, Korea.
Plant J. 2013 Feb;73(4):566-78. doi: 10.1111/tpj.12057. Epub 2012 Dec 10.
Flowering is exquisitely regulated by both promotive and inhibitory factors. Molecular genetic studies with Arabidopsis have verified several epigenetic repressors that regulate flowering time. However, the roles of chromatin remodeling factors in developmental processes have not been well explored in Oryza sativa (rice). We identified a chromatin remodeling factor OsVIL2 (O. sativa VIN3-LIKE 2) that promotes flowering. OsVIL2 contains a plant homeodomain (PHD) finger, which is a conserved motif of histone binding proteins. Insertion mutations in OsVIL2 caused late flowering under both long and short days. In osvil2 mutants OsLFL1 expression was increased, but that of Ehd1, Hd3a and RFT1 was reduced. We demonstrated that OsVIL2 is bound to native histone H3 in vitro. Chromatin immunoprecipitation analyses showed that OsVIL2 was directly associated with OsLFL1 chromatin. We also observed that H3K27me3 was significantly enriched by OsLFL1 chromatin in the wild type, but that this enrichment was diminished in the osvil2 mutants. These results indicated that OsVIL2 epigenetically represses OsLFL1 expression. We showed that OsVIL2 physically interacts with OsEMF2b, a component of polycomb repression complex 2. As observed from osvil2, a null mutation of OsEMF2b caused late flowering by increasing OsLFL1 expression and decreasing Ehd1 expression. Thus, we conclude that OsVIL2 functions together with PRC2 to induce flowering by repressing OsLFL1.
开花受促进和抑制因子的精细调控。拟南芥的分子遗传学研究已经证实了几种调节开花时间的表观遗传抑制剂。然而，染色质重塑因子在水稻（Oryza sativa）发育过程中的作用尚未得到充分探索。我们鉴定了一个促进开花的染色质重塑因子 OsVIL2（O. sativa VIN3-LIKE 2）。OsVIL2 包含一个植物同源域（PHD）指，这是一个保守的组蛋白结合蛋白基序。OsVIL2 中的插入突变导致长日和短日下开花延迟。在 osvil2 突变体中，OsLFL1 的表达增加，但 Ehd1、Hd3a 和 RFT1 的表达减少。我们证明 OsVIL2 可以在体外与天然组蛋白 H3 结合。染色质免疫沉淀分析表明，OsVIL2 直接与 OsLFL1 染色质结合。我们还观察到，野生型中 OsLFL1 染色质中 H3K27me3 的富集显著，但在 osvil2 突变体中这种富集减少。这些结果表明 OsVIL2 通过表观遗传抑制 OsLFL1 的表达。我们表明 OsVIL2 与 OsEMF2b 相互作用，OsEMF2b 是多梳抑制复合物 2 的一个组成部分。正如在 osvil2 中观察到的那样，OsEMF2b 的缺失突变通过增加 OsLFL1 的表达和减少 Ehd1 的表达导致开花延迟。因此，我们得出结论，OsVIL2 与 PRC2 一起通过抑制 OsLFL1 的表达来诱导开花。
