Advances on Factors Influencing Induction of Agrobacterium tumefaciens Virulence Genes

With advantages of easy-to-operate,low-cost,low copies and preferential integration of defined T-DNA into transcriptionally active regions of chromosomes without vector DNAs,Agrobacterium is employed for genetic modification of plants routinely.However,until recently,still there are a great many species recalcitrant to Agrobacterium-mediated transformation.Data suggest that the infection capability is designed by virulence(vir) genes of Ti plasmid outside of A.tumefaciens genome.Among all vir genes,virA and virG express constitutively,while other vir genes need phenolic compounds for induction.Besides,carbohydrates can enhance vir induction by phenolic compounds,while low phosphate and acidic pH environmental conditions may also increase induced expression of vir genes.In order to better utilize Agrobacterium and improve its efficiency for applications in research and biotechnology,molecular mechanisms for vir induction by factors such as phenolic compounds,carbohydrates,low phosphate,acidic pH conditions and incubation temperature are discussed.