切花菊腋芽伸长形成侧枝的分子调控机制研究

Cut chrysanthemum is one of the most important and preponderant exporting flowers in China. However, the plentiful lateral bud outgrowth is a severe problem in present single cut verities which not only impacts quality, but also restricts the high efficiency production. Therefore, revealing the molecular mechanism that controls the axillary branch development will lay the foundation for breeding the potential varieties without branches. Due to the complex genetic background in chrysanthemum, the inherent molecular mechanism of lateral branch development is largely unknown. Based on this, this project intends to use new strategies to get insights into the molecular regulation mechanism of axillary bud outgrowth in cut chrysanthemum. Achieving this goal will employ the use of plant materials with contrasting branching habits, i.e. cut chrysanthemum with few and profound branches, followed by sequential set of experiments. Firstly, the axillary meristems will be isolated to perform RNA-sequencing by combining laser capture micro-dissection with cell type-specific gene expression analysis. Secondly, we will identify the central modules and hub transcription factors involved in the hormonal signal transduction pathway with weighted gene co-expression network analysis (WGCNA). Thirdly, 3 hub transcription factors will be selected to verify their function in axillary bud outgrowth. Finally, we will construct the gene co-expression network by using correlation-based guilt-by-association approach with hub transcription factors and SL pathway genes as probes. Therefore, performing a series of studies will do a great deal to reveal the ultimate molecular regulation mechanism behind axillary bud outgrowth in cut chrysanthemum. The outcomes will definitely be a valuable asset inviting future perspectives to further unveiling of the molecular regularization mechanism of axillary bud control.

切花菊是我国主要切花和优势出口花卉之一。然而主栽的单头切花菊品种侧芽侧蕾发生严重，人工去除侧芽侧蕾成本高，成为制约切花菊高效生产的突出问题。解析切花菊侧枝形成的分子机制对于培育无侧枝切花菊新品种具有重要的意义。然而，由于切花菊遗传背景复杂，其腋芽伸长形成侧枝的分子调控机制尚不明确。基于此，本项目拟以申请者前期获得的珍贵的切花菊少分枝和多分枝材料为研究对象，首先采用冰冻切片显微切割技术分离腋生分生组织细胞进行转录组测序，然后采用基因共表达网络分析策略筛选与激素信号转导通路相关的核心模块和枢纽转录因子，并选择3个枢纽转录因子进行初步功能验证，最终，以筛选出的枢纽转录因子和与菊花侧枝形成紧密相关的独脚金内酯途径上的已知基因为探针构建基因共表达调控网络，初步阐明切花菊腋芽伸长形成侧枝的转录调控机制，为下一步深入解析切花菊侧枝形成的分子机理奠定基础。

切花菊是我国主要切花和优势出口花卉之一。然而主栽的单头切花菊品种侧芽侧蕾发生严重，人工去除侧芽侧蕾成本高，成为制约切花菊高效生产的一个突出问题。解析切花菊侧枝形成的分子机制对于培育无侧枝切花菊新品种具有重要的意义。本项目锁定菊花腋芽伸长形成侧枝这一关键发育时期，以温度和蔗糖为核心调控因子，通过形态学、解剖学、生理生化等水平研究探究了温度和蔗糖对切花菊腋芽伸长的影响，同时借助转录组测序和基因共表达网络分析策略挖掘核心模块及重要候选基因并开展了基因功能验证。通过研究发现高温抑制菊花腋芽伸长，但不同部位腋芽对高温的响应存在差异；温度通过叶片间接影响菊花腋芽活性；高温影响蔗糖在菊花不同部位腋芽中的分布，蔗糖的梯度分布可能是造成不同部位腋芽响应差异的一个原因；进一步研究发现蔗糖作为一种信号调节菊花腋芽释放和伸长；基于比较转录组学研究和基因共表达网络分析筛选出与腋芽伸长性状相关的核心模块和重要候选基因；在转录组数据分析基础上，在切花菊品种'神马'中克隆得到WOX基因家族11个成员的CDS全长序列，分别命名为CmWOX1-CmWOX11，qPCR组织特异性表达模式分析结合原位杂交分析确定CmWOX3基因在腋芽内表达，基因功能验证结果显示，过表达CmWOX3基因烟草株系腋芽数目增多、长度增长，同时过表达株系表现出开花延迟的表型特性。本研究初步揭示了切花菊腋芽伸长形成侧枝的分子调控机制，为深入解析切花菊腋芽伸长形成侧枝的分子机理奠定了基础，同时为切花菊分枝调控技术开发及通过分子手段培育无侧枝切花菊新品种提供了理论支持。