School of Biological Sciences, Seoul National University, Seoul, 08826, Korea.
Research Center for Plant Plasticity, Seoul National University, Seoul, 08826, Korea.
Sci Rep. 2022 Jun 29;12(1):10963. doi: 10.1038/s41598-022-15052-6.
Vernalization, an acceleration of flowering after long-term winter cold, is an intensively studied flowering mechanism in winter annual plants. In Arabidopsis, Polycomb Repressive Complex 2 (PRC2)-mediated suppression of the strong floral repressor, FLOWERING LOCUS C (FLC), is critical for vernalization and a PHD finger domain protein, VERNALIZATION INSENSITIVE 3 (VIN3), recruits PRC2 on FLC chromatin. The level of VIN3 was found to gradually increase in proportion to the length of cold period during vernalization. However, how plants finely regulate VIN3 expression according to the cold environment has not been completely elucidated. As a result, we performed EMS mutagenesis using a transgenic line with a minimal promoter of VIN3 fused to the GUS reporter gene, and isolated a mutant, hyperactivation of VIN3 1 (hov1), which showed increased GUS signal and endogenous VIN3 transcript levels. Using positional cloning combined with whole-genome resequencing, we found that hov1 carries a nonsense mutation, leading to a premature stop codon on the HEAT SHOCK TRANSCRIPTION FACTOR B2b (HsfB2b), which encodes a repressive heat shock transcription factor. HsfB2b directly binds to the VIN3 promoter, and HsfB2b overexpression leads to reduced acceleration of flowering after vernalization. Collectively, our findings reveal a novel fine-tuning mechanism to regulate VIN3 for proper vernalization response.
春化作用，即长期冬季寒冷后开花的加速，是冬季一年生植物中一种被深入研究的开花机制。在拟南芥中，多梳抑制复合物 2（PRC2）介导的对强花抑制物 FLOWERING LOCUS C（FLC）的抑制对于春化作用至关重要，并且一个 PHD 指结构域蛋白 VERNALIZATION INSENSITIVE 3（VIN3）将 PRC2 募集到 FLC 染色质上。发现 VIN3 的水平逐渐增加，与春化过程中的寒冷期长度成比例。然而，植物如何根据寒冷环境精细地调节 VIN3 的表达尚未完全阐明。因此，我们使用带有 VIN3 最小启动子与 GUS 报告基因融合的转基因系进行 EMS 诱变，并分离出一个突变体，即 VIN3 过度激活 1（hov1），其表现出增加的 GUS 信号和内源性 VIN3 转录本水平。通过定位克隆结合全基因组重测序，我们发现 hov1 携带一个无义突变，导致编码抑制性热休克转录因子的 HEAT SHOCK TRANSCRIPTION FACTOR B2b（HsfB2b）上出现过早的终止密码子。HsfB2b 直接结合 VIN3 启动子，并且 HsfB2b 的过表达导致春化后开花的加速减少。总之，我们的发现揭示了一种新的精细调控 VIN3 以实现适当春化反应的机制。
