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异柠檬酸脱氢酶(isocitrate dehydrogenase,IcdH)催化异柠檬酸转化成α-酮戊二酸,参与碳代谢途径末端的三羧酸(tricarboxylic acid,TCA)循环。然而,编码异柠檬酸脱氢酶基因是否参与水稻条斑病菌(Xanthomonas oryzae pv.oryzicola,Xoc)的致病性,我们并不清楚。为了阐明IcdH的作用,通过同源重组技术获得了Xoc的icdH基因缺失突变体(RΔicdH),并对该突变体进行了相关功能研究。研究表明:该突变体不能利用苹果酸、丙酮酸和柠檬酸,在寄主水稻上的生长能力和致病力相对于野生型均显著降低,其游动性也显著减弱;功能互补子恢复RΔicdH的上述表型至野生型水平;Real-time PCR结果显示,六碳单糖、蔗糖、苹果酸、丙酮酸与柠檬酸能显著诱导icdH基因的转录表达;与水稻细胞互作时icdH基因受诱导表达,并受HrpX和HrpG负调控。这些结果说明:icdH基因是Xoc获取碳源和在寄主水稻上具有致病性所需的。
Isocitrate dehydrogenase (IcdH) catalyzes the conversion of isocitrate to α-ketoglutarate, which participates in the tricarboxylic acid (TCA) cycle at the end of the carbon metabolism pathway. However, it is unclear whether the gene encoding isocitrate dehydrogenase is involved in the pathogenicity of Xanthomonas oryzae pv.oryzicola (Xoc). In order to elucidate the role of IcdH, the icdH gene deletion mutant (RΔicdH) of Xoc was obtained by homologous recombination technology, and the function of the mutant was studied. The results showed that the mutant could not utilize malic acid, pyruvic acid and citric acid, its growth ability and virulence on host rice decreased significantly compared with that of wild type, and its motility was also significantly weakened. The functional complements restored RΔicdH The results of Real-time PCR showed that the expression of icdH gene was significantly induced by six carbon monosaccharides, sucrose, malic acid, pyruvic acid and citric acid, while the expression of icdH gene was induced by interaction with rice cells , And negatively regulated by HrpX and HrpG. These results indicate that the icdH gene is required for Xoc to acquire a carbon source and to be pathogenic on host rice.