title: Artificial Agrobacterium tumefaciens strains exhibit diverse mechanisms to repress Xanthomonas oryzae pv. oryzae-induced hypersensitive response and non-host resistance in Nicotiana benthamiana.
abstract: Xanthomonas oryzae pv. oryzae (Xoo) rapidly triggers a hypersensitive response (HR) and non-host resistance in its non-host plant Nicotiana benthamiana. Here, we report that Agrobacterium tumefaciens strain GV3101 blocks Xoo-induced HR in N. benthamiana when pre-infiltrated or co-infiltrated, but not when post-infiltrated at 4 h after Xoo inoculation. This suppression by A. tumefaciens is local and highly efficient to Xoo. The HR-inhibiting efficiency of A. tumefaciens is strain dependent. Strain C58C1 has almost no effect on Xoo-induced HR, whereas strains GV3101, EHA105 and LBA4404 nearly completely block HR formation. Intriguingly, these three HR-inhibiting strains employ different strategies to repress HR. Strain GV3101 displays strong antibiotic activity and thus suppresses Xoo growth. Comparison of the genotype and Xoo antibiosis activity of wild-type A. tumefaciens strain C58 and a set of C58-derived strains reveals that this Xoo antibiosis activity of A. tumefaciens is negatively, but not solely, regulated by the transferred-DNA (T-DNA) of the Ti plasmid pTiC58. Unlike GV3101, strains LBA4404 and EHA105 exhibit no significant antibiotic effect on Xoo, but rather abolish hydrogen peroxide accumulation. In addition, expression assays indicate that strains LBA4404 and EHA105 may inhibit Xoo-induced HR by suppression of the expression of Xoo type III secretion system (T3SS) effector genes hpa1 and hrpD6. Collectively, our results unveil the multiple levels of effects of A. tumefaciens on Xoo in N. benthamiana and provide insights into the molecular mechanisms underlying the bacterial antibiosis of A. tumefaciens and the non-host resistance induced by Xoo.
authors.affiliation: Institute of Biotechnology, College of Agriculture and Biotechnology, Zhejiang University, 866 Yu Hang Tang Road, Hangzhou, 310058, China.
authors.forename: Wen
authors.initials: W
authors.lastname: Li
authors.affiliation: Institute of Biotechnology, College of Agriculture and Biotechnology, Zhejiang University, 866 Yu Hang Tang Road, Hangzhou, 310058, China.
authors.forename: Jia-Yi
authors.initials: JY
authors.lastname: Cao
authors.affiliation: Center of Analysis and Measurement, Zhejiang University, 866 Yu Hang Tang Road, Hangzhou, 310058, China.
authors.forename: You-Ping
authors.initials: YP
authors.lastname: Xu
authors.affiliation: Institute of Biotechnology, College of Agriculture and Biotechnology, Zhejiang University, 866 Yu Hang Tang Road, Hangzhou, 310058, China.|State Key Laboratory of Rice Biology, Zhejiang University, 866 Yu Hang Tang Road, Hangzhou, 310058, China.
authors.forename: Xin-Zhong
authors.initials: XZ
authors.lastname: Cai
mesh_terms: D016960:Agrobacterium tumefaciens / Q000502:physiology*; D004269:DNA, Bacterial / Q000235:genetics; D060467:Disease Resistance / Q000276:immunology*; D015964:Gene Expression Regulation, Bacterial; D006861:Hydrogen Peroxide / Q000378:metabolism; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology*; D010957:Plasmids / Q000235:genetics; D013997:Time Factors; D014026:Nicotiana / Q000276:immunology* / Q000382:microbiology*; D014974:Xanthomonas / Q000235:genetics / Q000254:growth & development / Q000502:physiology*
chemical_list: D004269:DNA, Bacterial; C036483:T-DNA; D006861:Hydrogen Peroxide
keywords: Agrobacterium tumefaciens; Nicotiana benthamiana; Xanthomonas oryzae pv. oryzae; antibiosis; hydrogen peroxide; hypersensitive response; non-host resistance