Study On A Rind Of Sensory Protein Genes Involved In Chemotaxis In XCC8004

Xanthomonas campestris pv. campestris（Xcc） is the causal agent of the black rot disease of cruciferous crops. Xcc as a model organism to study the molecular mechanisms between micro-organisms and host plant. It is of great significance to study pathogenic mechanism of Xcc for reducing economic loss in agriculture. At present, the significant of bacterial chemotaxis in ecology and etiology have been approved. Host plants contain a variety of chemicals in vivo, so chemotaxis is important for pathogens while avoiding disadvantages. According to the annotation of Xcc8004 genome, the coded products of XC₂307, XC₀286, XC₁074, XC₂313, XC₂504, XC₂304, XC₂316, XC₂320, XC₀336, XC₂306, XC₂136, XC₁801, XC₁937, XC₂315, XC₂314, XC₀843, XC₁412, XC₁414, XC₂308, XC₁413, XC₂223, XC₂309, XC₂311 and XC₀638 are chemotaxis proteins, all these genes mentioned above were deleted respectively by pK18mobSacB to assess their function, the phenotypes of these mutants were analysis.Virulence tests of these mutants on the host plant Chinese radish showed that, DM2223,DM1937 and DM2304 showed about 30% descent while DM2311 showed obviously reduced pathogenisty when comparing to the wild-type strain,and their complemented strains showed almost full virulence as wild-type strain. It suggests XC₂311, XC₂223,XC₂304 and XC₁937 are involed in virulence in Xcc. Beside,The growth of mutations DM2311, DM2223, DM1937 and DM2304 was inhibited in MMX medium comparing to wild-type strain, and their complementary strains can recovery the growth as the wild-type strain,the result revealed that XC₂311, XC₂223,XC₂304 and XC₁937 are involed in the growth of Xcc.The mutations of DM2311, DM2223, DM1937 and DM2304 results in reducing motility in 0.3% and 0.6% agar swimming medium, and the complementary strains can recovery motility as wild-type strain,the result revealed that XC₂311, XC₂223,XC₂304 and XC₁937 are involed in the motility of Xcc.The capillary tube method was applied on the chemotaxis analysis of the Xcc to thirty kinds of chemical substances （maltose, glucose, fructose, xylose, lactose, sucrose, ribose, arabinose, mannitol, tyrosine, arginine, alanine, leucine, serine, lysine, tryptophan, threonine, histidine, valine, glutamine, glutamic acid, aspartic acid, cysteine, proline, phenylalanine, isoleucine, magnesium chloride, calcium chloride, ammonium chloride and citric acid）, It was found that the Xcc showed obvious chemotaxis for 18 chemical substances.（sucrose, maltose, lactose, ribose, fructose, galactose, xylose, glucose, cysteine, proline, phenylalanine, glutamine, serine, isoleucine, arginine, leucine, calcium chloride, magnesium chloride）. To analyze how these 24 genes affect the chemotaxis of Xcc, we analyzed the chemotaxis of these mutants to the 18 kinds of chemical substances.Chemotaxis analysis showed that Xcc8004 mainly showed obvious chemotaxis to some sugars, amino acids, and inorganic ions which were involved in cell activities.When these deletion mutations compared with the wild-type strain, the HR, biofilm formation, heavy metal resistance, extracellular proteases, extracellular cellulase, extracellular amylase, EPS production have no significant difference.