title: hrp genes of Erwinia chrysanthemi 3937 are important virulence factors.
abstract: We developed improved virulence assays for Erwinia chrysanthemi 3937 on African violet varieties and devised a new method for the construction of precise bacterial gene knockouts. These methods were tested by constructing mutations in genes suspected to be involved with plant interactions. The virulence of the hrpG and hrcC mutant strains (both gene products presumed to be involved in protein secretion) was greatly reduced on leaves of semitolerant African violet varieties. An hrpN mutant strain produced delayed symptoms on African violet leaves and an hrpN delta pel (delta pel = five major pectate lyase genes deleted) double mutant was nonpathogenic. The hrcC and hrpG mutants did not produce a rapid hypersensitive response (HR) in tobacco, unlike the wild-type bacterium, and the hrpN mutant gave a reduced HR. The results, therefore, establish the importance of hrp genes in the virulence of E. chrysanthemi and their ability to elicit HR on nonhosts. The data also suggest that other effector proteins secreted by the Hrp system are required for full virulence and HR elicitation.
authors.affiliation: Department of Plant Pathology, University of California, Riverside 92521, USA.
authors.forename: Ching-Hong
authors.initials: CH
authors.lastname: Yang
authors.forename: Marina
authors.initials: M
authors.lastname: Gavilanes-Ruiz
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Okinaka
authors.forename: Regine
authors.initials: R
authors.lastname: Vedel
authors.forename: Isabelle
authors.initials: I
authors.lastname: Berthuy
authors.forename: Martine
authors.initials: M
authors.lastname: Boccara
authors.forename: Jason Wei-Ta
authors.initials: JW
authors.lastname: Chen
authors.forename: Nicole T
authors.initials: NT
authors.lastname: Perna
authors.forename: Noel T
authors.initials: NT
authors.lastname: Keen
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D016974:Dickeya chrysanthemi / Q000201:enzymology / Q000235:genetics* / Q000472:pathogenicity; D005798:Genes, Bacterial / Q000235:genetics; D019684:Magnoliopsida / Q000382:microbiology; D008969:Molecular Sequence Data; D009154:Mutation; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000382:microbiology; D017422:Sequence Analysis, DNA; D014026:Nicotiana / Q000382:microbiology; D014157:Transcription Factors; D014774:Virulence / Q000235:genetics
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004269:DNA, Bacterial; C102404:HrpG protein, Xanthomonas campestris; D014157:Transcription Factors; C075462:harpin protein, Erwinia amylovora; C087295:HrpZ protein, Pseudomonas syringae