Mutation of Xanthomonas hrpG Gene and Its Effect on Pathogenicity
Soybean bacterial spot disease is one of the major diseases that seriously damage the soybean yield.The pathogens of this disease are Xanthomonas axonopodis pv.glycines(Xag)and Xanthomonas campestris pv.glycinea(NaKmo)Dye(Xcg),which are gram-negative bacteria of Xanthomonas.Gram-negative pathogens cause Type Ⅲ secretion systems(T3SS),host-dependent on the hrp gene,to inject virulence factors into host cells.This study is of great significance to advance the breeding progress of soybean bacterial spot disease.This study used Xagneau001,a bacterial leaf spot pathogen,isolated from Jiamusi region.Its genome had been sequenced,and the hrpG gene was found in genome.Further research on pathogenicity of gene hrpG is carried out in our subject group.The mutant Xag△hrpG was constructed by triparental mating,and the hrpG gene was successfully knocked out by PCR detection and DNA sequencing.12 genetic backgrounds of different soybean germplasms were inoculated the wild type strain Xagneau001 and the mutant strain Xag△hrpG,respectively.The results showed that after inoculation of soybean with Xag△hrpG,the onset time of the spotted disease was prolonged,the progress was slowed down,and the pathogenicity was significantly reduced.The number of pathogenic bacteria per unit area of diseased leaves after 4 days was counted.The number of pathogenic Xag△hrpG pathogens was lower than that of wild-type Xagneau001.This result shows that Xag△hrpG is less pathogenic to soybean than wild-type Xagneau001.The hrpG enhances the pathogenicity of soybean bacterial spot disease.
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