Analysis Of The Gene Relating To Pathogenesis Of Ralstonia Solanacearum And Its Pathogenic Differences

Ralstonia solanacearum is a world-wide spread phytopathogenic bacterium thatcauses a bacterial wilt disease with deadly effects on many economically importantcrops and ornamentals. The genome of R. solanacearum strain has a size of5.8Mbwith a high (G+C) content and a coding potential for approximately5120proteins. R.solanacearum is described as a species-complex bacterium, therefore, manytechnology are applied to identify this bacterium. The products of type Ⅲ hrp sectionsystem, extrapolysaccharide, extracellular protein, cell wall degrading enzymes suchas pectinolytic and cellalolytic enzymesconstituted are the major factors for thepathogenicity. All of these are mainly relates to the hrp gene cluster, avr gene andvirulence genes. The Type Ⅲ secretion system (T3SS) and Type Ⅱ secretion system(T2SS) that directly translocate effector proteins into the host cells are essential forthe development of disease. The virulence and pathogenicity genes of R.solanacearum are controlled by an elaborate sensory network. The system usesPhcA concentration as a core to regulate the expression of pathogenic factors, andthus the growth status of bacteria.In this study, the special primer is used to identify R. solanacearum strains, inwhich84strains of R. solanacearum from different host plants in the Fujian provinceare identified with a specific band in the location of504bp. Meanwhile, the geneticdiversity of these R. solanacearum strains is assessed by Box element polymerasechain reaction (BOX-PCR) and Repetitive Extragenic Palindromic polymerase chainreaction (REP-PCR) method. Bases on their genomic fingerprints,19specific bandsare amplified in the BOX-PCR and20specific bands are amplified in the REP-PCR. The cluster analysis showes that the genetic diversity of R. solanacearum isconcerned with geographic origin and host plants, respectively. The different hostplants playes a leading role in the genetic difference of R. solanacearum, while thedifference of regions is mainly provided by the BOX-PCR, and the difference of hostplants is mainly provided by REP-PCR. At the same time, there are some specialfragments of R. solanacearum from different regions in BOX-PCR patterns. Moreover,there are also some special fragments of R. solanacearum from different host inREP-PCR patterns. Therefore, R. solanacearum from different regions and hosts canbe identified by these special fragments. All of results indicates that REP-PCR andBOX-PCR can provide an alternative way for the study of genetic diversity of R.solanacearum.The attenuation index to distinguish the pathogenicity for R. solanacearum isbased on the TTC cultural medium and the infection mortality to the host. The R.solanacearum virulent strain is recognized by the index less than0.714and all oftomato are basically severe death; Then the R. solanacearum avirulent strain by thathigher than0.833and all of tomato are not death; However, the attenuation index of R.solanacearum between0.714and0.833that the pathogenicity is between virulentand avirulent. The results of pathogenicity test correspond with the cluster result ofattenuation index, which is showed that the pathogenicity of R. solanacearum has adirect connection to its attenuation.The mechanism of pathogenesis of R. solanacearum is very complex. It isshowed that hrp maybe not play an important part in the pathogenesis of R.solanacearum, however, phcA is playing an important part in the pathogenesis of R.solanacearum. The reason why the pathogenesis of R. solanacearum becomeavirulent strain is that phcA is inserted by ISRso21and phcA become inactivation.The frequency of ISRso21positive strains from Minbei areas of Fujian Province is higher than that from other areas in this research. There is significant difference of thedistribution of ISRso21in R. solanacearum from different geography. Therefore, thepresent of ISRso21in R. solanacearum might be associated with geographic origin.Moreover, the different insertion sites of ISRso21in R. solanacearum are associatedwith the different pathogenicity of R. solanacearum. The cointegrate resolution proteinT, methyltransferase, integrase catalytic region, DNA-dependent RNA polymerase,PBCV-1DNA ligase, HK97family phage protein, caudovirus prohead protease andhypothetical protein Bmul₀496are also playing an important part in the pathogenesisof R. solanacearum.According to the result of attenuation index, pathogenesis and the pathogenesisof gene, there are identified7different pathogenesis of R. solanacearum, which arecompared with the characteristics of physiology and biochemisty. There are differentin the grew rate between different pathogenesis of R. solanacearum. Moreover, theposition and the values of the maximum absorption peak are different in differentpathogenesis of R. solanacearum. Meanwhile, the kinds of extracellular proteins aredifferent in different pathogenesis of R. solanacearum, which the kinds of extracellularproteins are the most in the R. solanacearum virulent strains, and the kinds ofextracellular proteins are the least in the R. solanacearum avirulent strains.