赤霉素受体蛋白GID1s参与光周期途径在菊花成花转化中的作用机制

Chrysanthemum is an important ornamental crop worldwide, is a plant in which short-day hastens time to flowering. The year-round production of chrysanthemum depends mainly on artificial photoperiod regulation, which is not only time-consuming but also power-wasting. Therefore, studying on the mechanisms of flowering, controling flower quality, as well as creating photoperiod-insensitive germplasms are important aspects in the research filed of chrysanthemum. Our previous work demonstrated that CO family member BBX24 in chrysanthemum modulates flowering transition under non-inductive long-day condition through gibberellin pathway. In addition, gibberellin receptors GID1s as downstream genes of BBX24, participate in promoting flowering of chrysanthemum. Here, we aim to elucidate the regulatory mechanism of GID1s participating in photoperiod pathway to influence the flowering time of chrysanthemum on the transcriptional and post-transcriptional levels. Our results will be valuable for understanding the molecular mechanism of flowering in the typical obligate short-day plant chrysanthemum, and will provide the candidate genes for breeding photoperiod-insensitive chrysanthemum cultivars. Meanwhile，it also provides new data for molecular biology analysis of chrysanthemum blossom.

菊花是全球重要的花卉作物，开花受短日照条件诱导。菊花的周年供应主要依赖于人工的光周期调节，不仅费时、费力而且能耗高。研究菊花的成花机理，控制开花品质，创制光周期不敏感菊花新种质一直是本领域研究的热点。申请者前期研究发现，光周期途径中的关键信号蛋白BBX24 (CO家族)可通过转调赤霉素（GA）途径实现菊花在非开花诱导长日照条件下的成花转变；而GA受体基因GID1s作为BBX24的下游组分，参与了对菊花提早开花的调节。本研究拟进一步解析GID1s信号通道调节菊花成花的分子调控模式，从转录和转录后层面，系统探索GID1s参与光周期途径的信号传导进而影响菊花成花的分子机制。本研究可为节能型精准调控花期的周年生产提供理论依据，为培育光周期不敏感的菊花新品种提供基因储备，也为短日照植物菊花的开花生物学研究提供新数据。

针对菊花周年供应生产中能耗高的产业问题，从发掘菊花中感受日照变化和内源响应的GAs信号转导路径核心调控因子入手，探究了赤霉素受体蛋白CmGID1s基因家族参与光周期途径调节菊花生长和开花的分子机制。本研究首先从短日照条件下菊花开花前后的转录组数据库中筛选出3个赤霉素受体蛋白基因CmGID1家族成员，将之分别命名为CmGID1A、CmGID1B和CmGID1C，。三者均定位于细胞核和细胞质中。表达特性分析结果显示，CmGID1s在菊花不同器官中均有所表达，且均受GAs诱导下调。在菊花中对CmGID1s基因功能的检测结果显示，CmGID1s-RNAi转基因植株均表现为植株变矮和开花时间提前，其中CmGID1B-RNAi转基因植株的表型变化最显著，并且CmGID1BC-RNAi双沉默植株加重了这一表型，表明CmGID1s 基因参与了菊花的株高生长和成花转化的调节 且CmGID1B可能发挥主要作用，并和CmGID1C存在功能冗余。采用LC-MS/MS法检测CmGID1B-RNAi转基因植株中的GAs含量结果显示，具有活性的GAs成员GA1和GA4及其合成前体均显著降低，推测CmGID1B通过调节内源GAs含量参与了菊花的植株生长和成花转化。进一步对CmGID1B-RNAi转基因植株进行RNA-seq 分析，差异基因主要涉及光周期开花信号途径和激素信号之间的交叉互作。酵母单杂交筛选并经ChIP验证了CmGID1B的上游调节基因是蓝光受体CmPHR2和蓝光受体互作因子CmCIB1的复合体；双荧光素酶报告试验表明CmCIB1和CmPHR2互作共同激活CmGID1B的表达。酵母双杂交证明CmGID1B、C与DELLA的互作能力较强，而且对于活性GAs的亲和力也较强，表明赤霉素受体蛋白CmGID1B在短日照条件下受蓝光受体复合因子调控，通过与DELLA蛋白互作，激活成花素基因FT，进而调节菊花的开花和株高生长。本研究阐明了CmGID1s基因家族参与光周期途径调节菊花生长和开花的分子机理，发掘出菊花成花转化过程中一个重要的内源GAs响应调节因子CmGID1B，为利用基因工程手段培育光周期不敏感且可周年花期调控的菊花新品种提供理论基础和基因储备。