青枯雷尔氏菌温度相关致病基因yqhE功能研究

不同温度下青枯雷尔氏菌表达谱PPI网络分析发现，yqhE可能是青枯雷尔氏菌新的温度相关致病基因。克隆青枯雷尔氏菌CBM613的yqh E基因，结果发现该基因长度为831 bp，共编码276个氨基酸。基因敲除结果显示，28℃培养的yqhE突变株较野生型菌株致病力降低，病程延长，但并未彻底丧失致病力。20℃和28℃培养的yqh E突变株维生素C的生物合成皆被抑制；与28℃相比，20℃培养下野生型菌株维生素C的合成能力降低。突变株在20℃和28℃培养下甲基乙二醛（MG）和丙二醛（MDA）明显积累，其中20℃积累更多；20℃培养的野生型菌株MG和MDA比28℃积累更多。维生素C的生物合成被抑制导致青枯雷尔氏菌自由基清除能力减弱与氧化应激反应增强，MG和MDA积累产生细胞毒性，上述结果可能与28℃培养的突变株致病力减弱，20℃培养的野生型菌株致病力丧失有关。综上结果表明yqhE是青枯雷尔氏菌温度相关致病基因。

Functional Analysis of Temperature Related Pathogenic Gene yqhE in Ralstonia solanacearum

The protein-protein interoperability (PPI) network analysis of the expression profiles of Ralstonia solanacearum at different temperatures showed that yqhE could be a new temperature related pathogenic gene of Ralstonia solanacearum. the gene yqhE was cloned from Ralstonia solanacearum strain CBM613. The results showed that gene yqhE was 831 bp in length, encoding 276 amino acids. Its function was further confirmed by gene knock-out. The results showed that the pathogenicity of the yqhE^－ mutant cultured at 28 ℃ was decreased and the course of disease was prolonged compared with the wild-type strain. Vitamin C biosynthesis of yqhE^－ mutant cultured at 20 ℃ and 28 ℃ were inhibited. The vitamin C biosynthesis ability of the wild-type strain cultured at 20 ℃ was reduced compared with 28 ℃. Methylglyoxal (MG) and malondialdehyde (MDA) of yqhE^－ mutant significantly accumulated at 20 ℃ and 28 ℃. MG and MDA of the wild-type strain cultured at 20 ℃ accumulated more than at 28 ℃. The inhibition of vitamin C biosynthesis resulted in the weakening of radical scavenging ability and the enhancement of oxidative stress reaction in Ralstonia solanacearum. The accumulation of MG and MDA produced cytotoxicity. The above results could be related to the weakening of pathogenicity in yqhE^－ mutant cultured at 28 ℃ and the loss of pathogenicity in wild-type strain cultured at 20 ℃. In conclusion, yqhE could be a temperature related pathogenic gene in Ralstonia solanacearum.