Shanghai Key Laboratory of Bio-Energy Crops, School of Life Sciences, Shanghai University, Shanghai, 200444, China.
Shanghai Key Laboratory of Bio-Energy Crops, School of Life Sciences, Shanghai University, Shanghai, 200444, China.
Plant Sci. 2018 Jul;272:88-98. doi: 10.1016/j.plantsci.2018.04.009. Epub 2018 Apr 13.
Light is a critical external signal for seed germination. The photoreceptor phytochrome B (PHYB) perceives light stimulation and promotes seed germination during the early phase after imbibition. SOM is a CCH-type zinc finger protein and negatively regulates PHYB-mediated seed germination by controlling downstream gibberellic acid (GA) and abscisic acid (ABA) metabolism. As a small molecular signal, carbon monoxide (CO) has been reported to regulate seed germination under environmental stress, but the underlying mechanism remains unclear. In this study, we first found that CO enhanced PHYB-dependent seed germination, and red light irradiation increased the transcriptional level of gene encoding Heme oxygenase 1(HY1) for CO production, this process required PHYB. Pharmacological and genetic analyses revealed that CO signals repressed the transcriptional level of SOM to alter downstream GA/ABA metabolism related genes expression, ultimately relieving the inhibitory effect of SOM on seed germination. Furthermore, CO signals possibly recruited histone deacetylase 6 (HDA6) to the promoter region of SOM to decrease its expression by diminishing histone H3 acetylation levels at this locus. Taken together, our results propose a novel mechanism for CO signals in promoting light-initiated seed germination via recruiting HDA6 to epigenetically regulate SOM expression.
光是种子萌发的关键外部信号。感光受体光敏色素 B（PHYB）在吸水后早期感知光刺激，并促进种子萌发。SOM 是一种 CCH 型锌指蛋白，通过控制下游赤霉素（GA）和脱落酸（ABA）代谢来负调控 PHYB 介导的种子萌发。作为一种小分子信号，一氧化碳（CO）已被报道在环境胁迫下调节种子萌发，但潜在的机制仍不清楚。在本研究中，我们首先发现 CO 增强了依赖 PHYB 的种子萌发，红光照射增加了编码血红素加氧酶 1（HY1）的基因的转录水平，从而产生 CO，这一过程需要 PHYB。药理学和遗传学分析表明，CO 信号抑制了 SOM 的转录水平，从而改变了下游 GA/ABA 代谢相关基因的表达，最终解除了 SOM 对种子萌发的抑制作用。此外，CO 信号可能招募组蛋白去乙酰化酶 6（HDA6）到 SOM 的启动子区域，通过降低该基因座上组蛋白 H3 乙酰化水平来减少其表达。总之，我们的研究结果提出了一种新的机制，即 CO 信号通过招募 HDA6 来对 SOM 表达进行表观遗传调控，从而促进光起始的种子萌发。
