CsIVP调控黄瓜维管发育、器官形成和抗逆的分子机理研究

Cucumber (Cucumis stivus L.) is one of the major greenhouse vegetables in China. Over-application of chemical fertilizers and pesticides to vegetables not only increase the production costs, but also cause serious problems to vegetable safety and environment pollution. It is of critical importance to identify genes regulating nutrient use efficiency and stress resistance in cucumber, and to obtain new cucumber cultivars with high nutrient efficiency and stress resistance. The vascular system is responsible for delivering water and nutrients throughout the plant, and participates in abiotic and biotic defense-related processes. However, the molecular connection between vascular development and stress resistance is largely unknown. We identified a transcription factor CsIVP that is specifically expressed in vasculature in cucumber. Knock-down of CsIVP by RNAi causes severe vasculature disorganization and abnormal morphogenesis in cucumber. Furthermore, CsIVP-RNAi plants are low-nitrogen and downy mildew tolerant. These data suggested that CsIVP is involved in vascular development, organ morphogenesis and resistance regulation, but the specific molecular mechanism remains elusive. Thus, this project will utilize the methods and tools in molecular biology, biochemistry and vegetable physiology, through phenotype analyses, hormone responses, protein interactions, downstream targets identification, and molecular markers development, to explore the molecular mechanism of CsIVP in regulating vascular development, organ formation, nitrogen utilization and downy mildew resistance in cucumber, so that build the molecular link between organ development and stress resistance. The results obtained in this project will provide the theory basis and gene resources for molecular breeding for cucumber cultivars with high nutrient efficiency and stress resistance.

黄瓜是我国设施栽培的主要蔬菜种类，化肥和农药的过量使用不仅导致生产成本增加，而且存在严重的产品安全和环境问题。挖掘黄瓜自身养分高效利用和抗病基因，培育高效抗逆的黄瓜品种至关重要。维管系统不仅运输水分和养分，而且参与非生物和生物胁迫防御，但维管发育与植物抗病之间的分子联系研究甚少。我们前期研究发现黄瓜CsIVP转录因子在维管组织特异性表达，CsIVP-RNAi转基因植株维管系统紊乱，器官形态异常，耐低氮和抗霜霉病能力增强，表明CsIVP参与维管发育、器官形态建成和抗逆调控，但其具体的分子机理尚不清晰。因此，本课题拟利用分子生物学、生物化学、以及蔬菜生理学等方法，从表型分析、激素响应、互作蛋白鉴定、下游调控基因分析及分子标记开发等角度，深入研究CsIVP调控黄瓜维管发育、器官形态、氮素利用和抗霜霉病的分子机理，建立器官发育与植物抗逆之间的联系，为黄瓜高效抗逆育种提供理论依据和基因资源。

作物从野生物种驯化过程中提高了产量和品质，但也伴随着丧失了一些抗逆性状，使其更容易遭受生物和非生物胁迫。维管系统在植物发育和胁迫响应方面起着重要作用。黄瓜是重要的蔬菜作物，维管系统发达且拥有双韧维管束结构，挖掘以黄瓜为代表的维管发育和抗病之间的分子联系具有重要理论意义和应用前景。我们的研究发现黄瓜bHLH转录因子Cucumis sativa Irregular Vasculature Patterning (CsIVP) 在维管组织中特异性表达，CsIVP-RNAi转基因植株维管系统紊乱，器官形态异常，抗霜霉病能力增强。本项目深入研究并解析了CsIVP调控黄瓜维管发育和抗霜霉病的分子机理。研究中发现，CsIVP属于HECATE3 (HEC3)亚家族，与HEC1/2基因一起是在被子植物起源之前由HEC复制产生的。生化研究表明，黄瓜CsIVP直接结合在维管发育调节因子CsYAB5和CsBP以及生长素信号途径基因CsAUX4上并促进其表达。下游CsYAB5的干扰转基因植株产生与CsIVP-RNAi植株相似的表型，包括维管构型紊乱和器官形态异常。抗病机理研究表明，CsIVP干扰植株表现出抗霜霉病，水杨酸含量提高，其直接与水杨酸途径的负调节因子CsNIMIN1蛋白互作，进而调节黄瓜霜霉病抗性。因此，我们揭示了黄瓜中一个维管发育正向调控因子CsIVP，其通过CsYAB5介导的维管发育途径和水杨酸途径来协调黄瓜器官发育和霜霉病抗性，为培育高效抗逆的黄瓜新品种提供理论依据和基因资源。