Kim Sang Yeol, He Yuehui, Jacob Yannick, Noh Yoo-Sun, Michaels Scott, Amasino Richard
Department of Biology, Indiana University, Bloomington, 47405, USA.
Plant Cell. 2005 Dec;17(12):3301-10. doi: 10.1105/tpc.105.034645. Epub 2005 Oct 28.
Winter-annual accessions of Arabidopsis thaliana are often characterized by a requirement for exposure to the cold of winter to initiate flowering in the spring. The block to flowering prior to cold exposure is due to high levels of the flowering repressor FLOWERING LOCUS C (FLC). Exposure to cold promotes flowering through a process known as vernalization that epigenetically represses FLC expression. Rapid-cycling accessions typically have low levels of FLC expression and therefore do not require vernalization. A screen for mutants in which a winter-annual Arabidopsis is converted to a rapid-cycling type has identified a putative histone H3 methyl transferase that is required for FLC expression. Lesions in this methyl transferase, EARLY FLOWERING IN SHORT DAYS (EFS), result in reduced levels of histone H3 Lys 4 trimethylation in FLC chromatin. EFS is also required for expression of other genes in the FLC clade, such as MADS AFFECTING FLOWERING2 and FLOWERING LOCUS M. The requirement for EFS to permit expression of several FLC clade genes accounts for the ability of efs lesions to suppress delayed flowering due to the presence of FRIGIDA, autonomous pathway mutations, or growth in noninductive photoperiods. efs mutants exhibit pleiotropic phenotypes, indicating that the role of EFS is not limited to the regulation of flowering time.
需要经历冬季的寒冷才能在春季启动开花。在经历寒冷之前阻止开花是由于开花抑制因子开花位点C（FLC）的高水平表达。暴露于寒冷通过一个称为春化作用的过程促进开花，该过程通过表观遗传抑制FLC的表达。快速循环种质通常具有低水平的FLC表达，因此不需要春化作用。对将冬性一年生拟南芥转化为快速循环类型的突变体进行的筛选鉴定出一种假定的组蛋白H3甲基转移酶，它是FLC表达所必需的。这种甲基转移酶，即短日照早花（EFS）中的损伤，导致FLC染色质中组蛋白H3赖氨酸4三甲基化水平降低。EFS也是FLC进化枝中其他基因表达所必需的，例如影响开花的MADS2和开花位点M。EFS允许几个FLC进化枝基因表达的需求解释了efs损伤抑制由于存在FRIGIDA、自主途径突变或在非诱导光周期下生长而导致的延迟开花的能力。efs突变体表现出多效性表型，表明EFS的作用不限于开花时间的调节。
