OsbHLH120调控旱稻根粗和根长的分子机理

Roots are the principal plant organs for nutrient and water uptake. A strong root system would enable a plant to extract more water and nutrients from the soil, which is important for good plant growth and increased yield under soil-related stresses. Thus, it is necessary to determine the main genetic determinants of the strong root system and to transfer these genes into lowland rice to improve their drought resistance. A novel QTL, qBRT9a, for root thickness and root length was cloned by our research group. A basic helix-loop-helix (bHLH) transcription factor, LOC_Os09g28210 (named as OsbHLH120) identified as a candidate gene regulates root growth confirmed by genetic transformation and correlation analysis. In this research, using over-expression and RNAi transgenic material, and qBRT9a introgression line, root architecture and the number and the length of cells in different regions of root tip will be investigated through root X-optical scanning imaging, stereoscope, and resin sections. The expression pattern, downstream genes, and protein interaction of OsbHLH120 will be researched using subcellular localization, GUS staining, qRT-PCR, ChIP-Seq, expression microarray, and GST pull-down. Then, cytological evidence and molecular pathway of that qRT9 promotes root growth and the value of qBRT9a in field breeding will be discussed. These results will provide a starting point for functional characterisation of the mechanism of root growth, drought resistance and molecular-assisted selection for improving drought resistance.

根系是植物吸收水分的主要器官，根系基因的克隆与分析是揭示根系发育和抗旱机制的主要途径。我们图位克隆了控制旱稻根粗和根长的QTL qBRT9a，遗传转化和关联分析证明了目的基因OsbHLH120控制根系发育。基于前期基础，本项目拟利用已获得的qBRT9a导入系、超表达和RNAi转基因材料等，采用根系X-光扫描成像、体视镜和超薄树脂切片观察根系构型及根尖各区域细胞数目和长度；通过亚细胞定位、GUS染色、qRT-PCR、ChIP-Seq、表达谱芯片、酵母双杂交与GST pull-down实验，分析OsbHLH120表达部位、对土壤干旱和激素的响应、调控的下游基因及互作蛋白，进而探明OsbHLH120参与根系发育的细胞学机制和分子调控网络，为解析作物根系发育、抗旱机制和培育节水抗旱稻奠定基础。

根系是植物吸收水分的主要器官,项目在图位克隆了控制旱稻根粗和根长的QTL qBRT9a的基础上，以OsbHLH120超表达、RNAi转基因植株、CAS9突变材料和对照植株为材料，发现不同材料的通气组织和根尖成熟区细胞存在差异，OsbHLH120可能是通过影响根尖细胞大小控制根系发育。亚细胞定位确定基因在细胞核中表达，对PEG和NaCl处理都有响应。DNA亲和纯化测序DAP-seq、水稻全基因组转录组测序和qRT-PCR试验，发现生长素响应因子OsIAA9和膨胀素EXPA23可能是OsbHLH120调控的下游基因。通过酵母双杂交结合BiFC实验，发现OsbHLH120与生长素通路基因SPT和OsbHLH107蛋白相互作用，揭示了OsbHLH120调节根系发育的分子调控路径。大田试验证明了旱稻OsbHLH120能提高根系发育，且能提高穗粒数和产量，研究结果为培育节水抗旱资源节约型水稻品种奠定基础。