title: Transcriptional Activation of Virulence Genes of Rhizobium etli.
abstract: Recently,Rhizobium etli, in addition toAgrobacteriumspp., has emerged as a prokaryotic species whose genome encodes a functional machinery for DNA transfer to plant cells. To understand thisR. etli-mediated genetic transformation, it would be useful to define how itsvirgenes respond to the host plants. Here, we explored the transcriptional activation of thevirgenes contained on theR. etlip42a plasmid. Using a reporter construct harboringlacZunder the control of theR. etli virEpromoter, we show that the signal phenolic molecule acetosyringone (AS) inducesR. etli virgene expression both in anR. etlibackground and in anAgrobacterium tumefaciensbackground. Furthermore, in both bacterial backgrounds, the p42a plasmid also promoted plant genetic transformation with a reporter transfer DNA (T-DNA). Importantly, theR. etli virgenes were transcriptionally activated by AS in a bacterial species-specific fashion in regard to the VirA/VirG signal sensor system, and this activation was induced by signals from the natural host species of this bacterium but not from nonhost plants. The early kinetics of transcriptional activation of the majorvirgenes ofR. etlialso revealed several features distinct from those known forA. tumefaciens: the expression of thevirGgene reached saturation relatively quickly, andvirB2, which inR. etliis located outside thevirBoperon, was expressed only at low levels and did not respond to AS. These differences invirgene transcription may contribute to the lower efficiency of T-DNA transfer ofR. etlip42a than of T-DNA transfer of pTiC58 ofA. tumefaciensIMPORTANCEThe region encoding homologs ofAgrobacterium tumefaciensvirulence genes in theRhizobium etliCE3 p42a plasmid was the first endogenous virulence system encoded by the genome of a non-Agrobacteriumspecies demonstrated to be functional in DNA transfer and stable integration into the plant cell genome. In this study, we explored the transcriptional regulation and induction of virulence genes inR. etliand show similarities to and differences from those of theirA. tumefacienscounterparts, contributing to an understanding and a comparison of these two systems. Whereas mostvirgenes inR. etlifollow an induction pattern similar to that ofA. tumefaciens virgenes, a few significant differences may at least in part explain the variations in T-DNA transfer efficiency.
authors.affiliation: Department of Biochemistry and Cell Biology, State University of New York, Stony Brook, New York, USA.|Department of Plant Pathology, College of Plant Protection, Nanjing Agricultural University, Key Laboratory of Monitoring and Management of Crop Diseases and Pest Insects, Ministry of Agriculture, Engineering Center of Bioresource Pesticide in Jiangsu Province, Nanjing, Jiangsu Province, China.
authors.forename: Luyao
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Biochemistry and Cell Biology, State University of New York, Stony Brook, New York, USA benoit.lacroix@stonybrook.edu.
authors.forename: Benoît
authors.initials: B
authors.lastname: Lacroix
authors.affiliation: Department of Plant Pathology, College of Plant Protection, Nanjing Agricultural University, Key Laboratory of Monitoring and Management of Crop Diseases and Pest Insects, Ministry of Agriculture, Engineering Center of Bioresource Pesticide in Jiangsu Province, Nanjing, Jiangsu Province, China.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Guo
authors.affiliation: Department of Biochemistry and Cell Biology, State University of New York, Stony Brook, New York, USA.
authors.forename: Vitaly
authors.identifier: http://orcid.org/0000-0003-2024-6844
authors.initials: V
authors.lastname: Citovsky
mesh_terms: D016960:Agrobacterium tumefaciens / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D007887:Fabaceae / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D011401:Promoter Regions, Genetic; D042163:Rhizobium etli / Q000235:genetics / Q000378:metabolism*; D014026:Nicotiana / Q000382:microbiology; D015533:Transcriptional Activation / Q000502:physiology*; D014774:Virulence
chemical_list: D001426:Bacterial Proteins
keywords: Rhizobium etli; plant genetic transformation; virulence genes