Conservation and diversity of the Agrobacterium type VI secretion systems involved in interbacterial competition
M. Santos (1), S. Cho (1), H. Chang (1), C. Kuo (1), E. Lai (1) (1) Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Taiwan

Type VI secretion system (T6SS) is widely distributed in gram-negative proteobacteria and capable to inject effectors/toxins into eukaryotic or prokaryotic cells for survival and fitness. The Agrobacterium tumefaciens C58 strain T6SS can utilize DNase effectors as an antibacterial weapon for interbacterial competitive advantage during plant infection. So far, little is known about the conservation and diversity of T6SS gene cluster and effectors among different Agrobacterium strains. Comparative sequence analysis of 9 A. tumefaciens strains from 4 different genospecies revealed the presence of one main T6SS gene cluster and at least one to multiple vgrG genes in all analyzed strains. Futhermore, the 14 essential components required for T6SS activity are highly conserved, whereas the vgrG-associated genes are highly variable. The notion that the vgrG-associated genes usually encode toxin/effector proteins has led us to speculate that these Agrobacterium strains produce diverse effectors. All analyzed Agrobacterium strains are active in type VI secretion and confer differential T6SS-dependent antibacterial activity against Escherichia coli. Further competitive outcomes between different Agrobacterium strains in planta showed that Agrobacterium strains harboring different vgrG-associated genes are incompatible with each other. The unique feature of the vgrG-associated genes suggested that different Agrobacterium strains adopt different toxin-immunity gene sets for interbacterial competition in its host plant or specific niche.

Abstract Number: P11-374
Session Type: Poster