| Plant bacterial wilt caused by Ralstonia solanacearum is serious and difficult to control,especially causing great losses to the production of Solanaceae crops such as tomato and potato.The host range of Ralstonia solanacearum is wide,the genetic characteristics of bacterial population are complex,and the related pathogenic factors and host adaptability have not been fully analyzed.In our laboratory,a highly pathogenic strain named ES5-1 was isolated from tomato bacterial wilt samples.which can overcome the disease resistance of resistant variety H7996.The biological characteristics,host range and genetic evolution status of ES5-1 strain were analyzed.The genome of the strain was determined and assembled.The type III effector proteins that may be related to strong pathogenicity were screened.The knockout mutants of candidate effector proteins were constructed,and their potential functions in pathogenicity were analyzed.This study provides a new clue for exploring the host range affected by the effector protein of Ralstonia solanacearum.The specific research results are as follows:It was found that the tomato bacterial wilt isolate ES5-1 had strong pathogenicity to H7996,H7998,XM-5 and TA08,and could infect potato and pepper;Genetic evolution analysis showed that strain ES5-1 belonged to phylotypes Ⅱ sequence suqver 1.It was further found that 11 phylotypes Ⅱ strains had strong pathogenicity to tomato disease resistant variety H7996;The biological characteristics showed that the colony growth rate of ES5-1 was slower than that of model strain GMI1000;The colony color was lighter than that of GMI1000;ES5-1 can induce strong cell necrosis in tomato leaves of different varieties;The full-length genome of ES5-1 was sequenced and spliced.It was found that five effector proteins existed specifically in ES5-1,and 16 effector proteins existed in GMI1000 but not in ES5-1.The effector proteins specifically encoded by ES5-1 were named RipS1-RipS5 respectively,and their knockout mutants were constructed.The pathogenicity of Δrips1、Δrips4 andΔrips5 was not significantly different from wild type.The pathogenicity ofΔrips2 was weaker than wild-type strain,and Δrips2 belonged to the transporter of type III secretion system;The pathogenicity of Δrips3 to tomato disease resistant variety H7996 was significantly weaker than wild type,and The survival competitiveness of Δrips3 in tomato was also significantly lower than wild type;The protein has a novel ubiquitin ligase domain,which is located in the cell membrane.It can inhibit the outbreak of reactive oxygen species and the activation of MAPK when expressed in Arabidopsis protoplast.The above results show that RipS3 can affect the immune response of plants and participate in the pathogenic process of ES5-1 strain against tomato disease resistant variety H7996.This study shows that strain ES5-1 can overcome the disease resistance of tomato disease resistant varieties.Its genome encodes a specific type III effector protein different from the model strain.Rips3 may help the strain overcome tomato resistance by inhibiting plant immune response.The related target proteins and molecular action mechanism in plants need to be further explored. |
