外源SA与JA协同增强黄瓜对根结线虫的抗性效应及其调控机制研究

Development and utilization for resistance to root-knot nematodes (RKN) in wild Cucumis species is effective to cucumber genetic improvement. Our previous results revealed that the resistance in wild cucumber is mostly characterized by limited invasion of nematodes, hypersensitive responses and inhibition of nematodes feeding. Recent RNA-Seq data showed that some genes involved in salicylic acid (SA) and jasmonic acid (JA) signaling were significantly altered in expression. However, the underlying mechanism remains unclear. In the present study, CmR07 and CmS12 derived from C. metuliferus, exhibiting high resistance and susceptibility to Meloidogyne incognita respectively, will be used to analyze and determine the effect of exogenous SA and JA synergisticly on the enhancement of cucumber resistance to the pest. Afterwards, gene expression profiling related resistance will be established for investigating the relationship between SA and JA in compatible and incompatible interactions of M. incognita with cucumber using reverse transcription-PCR (RT-PCR) and quantitative PCR (qPCR). Moreover, research on CmWRKY20 protein in distribution in root cells, transcriptional activation activity and binding ability with target gene will be carried out to elucidate its regulation roles playing in cucumber nematode resistance. The expected results of the study will provide comprehensive insights into the resistance mechanisms involved in wild cucumber-RKN interaction. Related results obtained from the study can also add to the knowledge base beneficial for research and development of broad-spectrum nematicides, and this should have important theoretical values and potential application prospects in controlling nematodes in the future.

野生抗源的发掘与利用是黄瓜根结线虫抗性遗传改良的有效途径。项目组前期研究发现，抗线虫侵入、过敏反应与抑制线虫取食是野生黄瓜发生根结线虫抗性的主要特征，近期基于RNA-Seq检测到线虫抗性中与SA/JA信号传导相关的基因显著差异表达，但其深入的作用机制尚不明晰。本项目拟以高抗根结线虫的CmR07与高感株系CmS12为试材，通过外源SA与JA增强黄瓜对根结线虫抗性的效应分析，明确SA与JA对根结线虫抗性的协同效应；采用RT-PCR与qPCR构建抗性相关的基因表达谱，解析黄瓜-根结线虫亲和与非亲和反应中SA与JA的互作关系；通过CmWRKY20的细胞分布、转录激活活性及其与靶基因的结合能力研究，探明CmWRKY20在黄瓜根结线虫抗性中的调控作用。该项研究将为深入阐明野生黄瓜抗线虫机制奠定基础，相关结果可为研发广谱高效的防线虫制剂提供科学依据，具有重要的理论价值和潜在的应用前景。

水杨酸（SA）与茉莉酸（JA）是重要的抗性信号分子，WRKY类转录因子在SA/JA信号网络系统中发挥重要作用。通过研究SA 与JA 在黄瓜根结线虫（RKN）抗性信号网络中的作用与互作关系，可为黄瓜RKN抗性反应的调控提供有效机制。本项目通过外源SA 与JA对黄瓜RKN的抗性效应分析，发现SA 与JA处理能够协同增强NPR1、AOS、PAL等防卫基因的表达，从而提高了野生黄瓜对RKN的抗性；通过构建野生黄瓜RKN抗性相关的基因表达谱，明确了在野生黄瓜RKN抗性中SA与JA既有协同效应又有拮抗作用，确定了协同效应与拮抗作用的临界阈值；克隆获得了与RKN抗性密切相关的CmWRKY20转录因子，明确了基因结构及其表达模式，确定了CmWRKY20在细胞中的分布定位与转录激活活性；SA和JA可引起野生黄瓜RKN抗性协同效应，CmWRKY20通过依赖SA/JA信号通路参与野生黄瓜RKN抗性调控。这些研究结果有助于阐明黄瓜与根结线虫非亲和互作的分子机理，具有重要的理论价值，相关应用研究可为根结线虫的绿色防控奠定基础，具有潜在的应用前景。