The Agrobacterium VirE2 effector interacts with multiple members of the Arabidopsis VIP1 protein family

Summary T-DNA transfer from Agrobacterium to its host plant genome relies on multiple interactions between plant proteins and bacterial effectors. One of such plant proteins is the Arabidopsis VirE2 interacting protein (AtVIP1), a transcription factor that binds A. tumefaciens C58 VirE2, potentially acting as an adaptor between VirE2 and several other host factors. It remains unknown, however, whether the same VirE2 protein has evolved to interact with multiple VIP1 homologs in the same host, and whether VirE2 homologs encoded by different bacterial strains/species recognize AtVIP1 or its homologs. Here, we addressed these questions, by systematic analysis - using the yeast-two-hybrid and co-immunoprecipitation approaches - of interactions between VirE2 proteins encoded by four major representatives of known bacterial species/strains with functional T-DNA transfer machineries and eight VIP1 homologs from Arabidopsis and tobacco. We also analyzed the determinants of the VirE2 sequence involved in these interactions. These experiments showed that the VirE2 interaction is degenerate: the same VirE2 protein has evolved to interact with multiple VIP1 homologs in the same host, and different and mutually independent VirE2 domains are involved in interactions with different VIP1 homologs. Furthermore, the VIP1 functionality related to the interaction with VirE2 is independent of its function as a transcriptional regulator. These observations suggest that the ability of VirE2 to interact with VIP1 homologs is deeply ingrained into the process of Agrobacterium infection. Indeed, mutations that abolished VirE2 interaction with AtVIP1 produced no statistically significant effects on interactions with VIP1 homologs or on the efficiency genetic transformation. This article is protected by copyright. All rights reserved.