Study On The Effect Of Bismerthiazol To Xanthomonas Oryzae Pv.Oryzae Extracellular Polysaccharide

Rice bacterial blight caused by Xanthomonas oryzae pv.oryzae is one of the three major rice diseases;which does harm to rice growth and cause a decline in yield and quality of rice.Since the 80's of last century,in our country the main emergency measures to control rice bacterial blight epidemic hazards is spraying bismerthiazol chemical control.Our laboratory studies have shown that,the pathogenicity factor of Xanthomonas oryzae pv.oryzae,extracellular polysaccharide,which is antagonistic to biological activity of bismerthiazol,but the mechanism of that inhibits the growth of bacteria and prevents disease is still not clear.The results of this study show that bismerthiazol can inhibit the biosynthesis of extracellular polysaccharide in Xanthomonas oryzae pv.oryzae,with the concentration increased,the inhibition rate of extracellular polysaccharide increased.Treated with 6.25?g/ml,12.5?g/ml,25?g/ml,50?g/ml of bismerthiazol,the inhibition rate of extracellular polysaccharide is 13.28%,41.62%,64.13%,90.37%;but the inhibition of cell growth is 13.24%,28.73%,59.66%,82.46%,the inhibition of extracellular polysaccharides is obviously higher than that of cell growth when the concentration of bismerthiazol is higher than 12.5?g/ml.Treated with 12?g/ml of bismerthiazol,the expression of gum gene cluster has different degree of reduction,which is consistent with agents inhibit the biosynthesis of EPS.To further study the relationship between the gum gene cluster and the bismerthiazol sensitivity and pathogenicity.Except gumD ? gumJ,we obtain 11 knock-out mutants,?gumB??gzumC??gumE??gumF??gumG??gumH??gumI??gumK??gumL??gumM?AgumN.Compared to wild-type strain ZJ173,the results show that the pathogenicity of these mutants(?gumB??gumE??gumM??gumC??gumH)reduced 80%--90%,the colony morphology of the mutants become wizened,and the yield of extracellular polysaccharide reduced,and the synthesis of biological membrane is decreased,and the growth rate and motility have different degrees of reduce.These results show that the five genes(gumB?gumE?gumM?gumC and gumH)have an important function in the pathogenic process of Xauthomonas oryzae pv.oryzae.The results of drug susceptibility of gum gene mutants to bismerthiazol and its homologues amicarthiazol and ATDA show that,compared with the wild-type ZJ173,the sensitivity of ?gumH to bismerthiazol,ATDA and amicarthiazol is reduced;the sensitivity of ?gumC to bismerthiazol and amicarthiazol is reduced,but the sensitivity to ATDA is increased;the sensitivity of ?gumI to bismerthiazol is increased,and the sensitivity to amicarthiazol is increased,but ?gumI has no change to ATDA.These results mean that the gum gene is not only associated with thiazole fungicide sensitivity,but also has some effects on the regulation of the level of susceptibility gene of different thiazole derivatives.