EF2调节拟南芥开花时间的分子机制

The timing of flowering, the transition from vegetative to reproductive development in plants, is determined by genetic pathways that integrate endogenous and environmental signals. Flowering time is an important agronomic trait for regional and seasonal adaption, and heading at the proper time is a critical step for successful grain production. The histone methylation and histone variant H2A.Z are critical in flowering-time regulation in Arabidopsis. Here, we found an early flowering 2 (ef2), which exhibited the early flowering phenotype after crossed ef2 into FRIGIDA. EF2, encoding a SET domain protein, a putative histone lystine methyltransferase. EF2 interacts with ARP6, which is a subunit of SWR1. The possible genetic interaction between EF2 and APR6 was investigated by crossing apr6 into FRI ef2. The FRI ef2 arp6 double mutant displayed the early flowering, which is similar to that of FRI ef2, suggesting that EF2 acts the same pathway as ARP6 in flowering time. We investigated the distribution of H2A.Z by chromatin immunoprecipitation (ChIP), followed by quantitative PCR measurement of DNA enrichment. H2A.Z levels were reduced in ef2 mutant, suggesting that EF2 was involved in histone variant H2A.Z regulation. This study is going to study the roles of EF2 in flowering time and figure out the relationship between histone methylation and H2A.Z.

开花是植物营养生长至生殖生长的重要转变过程，由外界环境和内在生理状态共同调控完成，植物能否在恰当时间开花，决定了植物能否有效产生种子，延续下一代。组蛋白甲基化和组蛋白变体H2A.Z是调控拟南芥开花的重要方式之一，我们前期通过筛选到突变体early flowering 2 (ef2)，ef2在FRIGIDA背景下有明显的早花表型。EF2编码SET结构域蛋白，酵母双杂交和蛋白体外pull-down研究显示：EF2能与SWR1复合体的ARP6亚基直接互作。FRI ef2 arp6的表型与FRI ef2表型一致，表明二者在同一个开花途径，共同调控着FLC的表达水平。进一步研究显示：ef2突变体内H2A.Z的水平降低，表明EF2能够调控H2A.Z的富集。本研究拟在已有的基础上，阐述EF2调控拟南芥开花时间的机理，探究组蛋白甲基化和H2A.Z协同调控的分子机制。

开花是营养生长至生殖生长转变的过程，受外在环境和内在遗传因素共同调控。COOLAIR是FLOWERING LOCUS C (FLC)位点，反向转录的长非编码RNA，促进H3K27me3修饰，抑制FLC的表达。然而，COOLAIR如何促进H3K27me3修饰还不清楚。在本项目的资助下，我们发现RNA结合蛋白FCA一方面能够直接结合COOLAIR，另一方面FCA与PRC2复合体EF2 (CLF)直接互作，继而促进FLC位点的H3K27me3修饰。在COOLAIR缺失的时候，降低FCA和CLF在FLC位点富集以及H3K27me3的水平。SSU72能够与FCA直接互作，并且能够抑制FCA与COOLAIR结合。功能缺失的SSU72具有开花早的表型，并且促进FCA和CLF在FLC位点富集以及H3K27me3的水平。我们的研究阐述了长非编码RNA调控组蛋白H3K27me3的内在机制。