水稻条斑病菌异柠檬酸脱氢酶基因的功能解析

Xanthomonas oryzae pv. oryzicola is the important bacterial pathogen, causing serious bacterial leaf streak (BLS) in rice. The ability to acquire carbohydrate is essential for a pathogen to propagate and successfully establish an infection relationship in host plant. The applicant previously study that scan a novel virulence factor, isocitrate dehydrogenase (IcdH), from a mutant library of Xanthomonas oryzae pv. oryzicola. The mutation in icdH, not only remarkably impaired bacterial pathogenicity, virulence in planta, but also observably reduced bacterial growth capability in rice. In addition, the mutagenesis in this unique icdH gene of Xanthomonas oryzae pv. oryzicola also regulated the transcription expression level of the key genes, such as rpfF, rpfG and clp, in DSF signaling pathway. But the molecular mechanism is still not clear. This project draws up to utilize carbon metabolic pathway analysis, virulence-associated factors detection, and DSF detection and analysis to research the correlation between icdH and virulence, quorum sensing DSF signal molecules. By analyzing the representative genes transcription expression, ascertains the regulation relationship between the carbon metabolism and the hrp gene. Ultimately, via the above analysis roundly reveals the molecular mechanism of the icdH in the carbon metabolic pathways involved in full virulence of Xanthomonas oryzae pv. oryzicola. All these may prove important scientific significance and practical value in revealing the mechanism of plant and pathogenic bacteria molecular interaction, screening potential drug target, and carrying out efficient biological control strategy.

水稻条斑病菌是水稻上重要的细菌病原物，引起水稻细菌性条斑病。营养的获取对于病原物在寄主水稻体内生长繁殖、成功建立侵染关系异常重要。申请人前期研究，从水稻条斑病菌突变体库中扫描出新的毒性因子-编码异柠檬酸脱氢酶（isocitrate dehydrogenase, IcdH），icdH突变，病原菌的致病性、全毒性、在水稻组织中的生长能力均显著下降，同时它还调控着DSF信号通路关键基因rpfF、rpfG、clp的转录表达，但其分子机理尚不清楚。本项目拟通过碳代谢途径分析、毒性相关因子检测以及DSF定性/量检测等手段，分析icdH与毒性、群体感应DSF信号分子的关联性；借助代表性基因转录分析，明确碳代谢与hrp基因表达之间的调控关系；最终全面解析icdH参与条斑病菌全毒性的分子机理。这对于揭示病原细菌与植物互作的分子机理、筛选药物靶标、开展高效的生物防治策略等，均具有重要的科学意义和实践价值。

水稻条斑病菌是水稻上重要的细菌病原物，其通过五条碳代谢途径（糖酵解、磷酸戊糖、糖异生、ED途径及三羧酸循环）不断从寄主水稻体内吸取营养物质（碳源），以便能在寄主体内大量生长繁殖、并成功建立侵染关系，从而引起水稻病害症状。本项目主要研究了碳代谢途径中编码催化酶基因在致病性中的功能作用，以及其与hrp系统、群体感应系统的关联性。本研究不仅详细地阐述了三羧酸循环中重要基因icdH在致病性中的作用及其它生物学特性；而且还选取糖酵解与糖异生途径中的重要基因xanA和pgi，以及ED与磷酸戊糖途径中的关键基因zwf进行了详细研究。这些研究结果揭示：碳代谢途径中编码催化酶基因因其位置不同而作用差异显著，其对病原菌致病性及毒性因子合成的贡献、以及其与hrp系统、群体感应系统的关联系因位置不同而已。这些不仅丰富我们对碳代谢途径功能与作用的理解与认识，而且为全面解析碳代谢途径参与水稻条斑病菌全毒性的分子机理及可能的利用碳代谢途径防控水稻细菌病害奠定基础。