Agrobacterium Induces Expression of a Host F-Box Protein Required for Tumorigenicity

Agrobacterium exports DNA into plant cells, eliciting neoplastic growths on many plant species. During this process, a Skp1-Cdc53-cullin-F-box (SCF) complex that contains the bacterial virulence F-box protein VirF facilitates genetic transformation by targeting for proteolysis proteins, the Agrobacterium protein VirE2 and the host protein VIP1, that coat the transferred DNA. However, some plant species do not require VirF for transformation. Here, we show that Agrobacterium induces expression of a plant F-box protein, which we designated VBF for VIP1-binding F-box protein, that can functionally replace VirF, regulating levels of the VirE2 and VIP1 proteins via a VBF-containing SCF complex. When expressed in Agrobacterium and exported into the plant cell, VBF functionally complements tumor formation by a strain lacking VirF. VBF expression is known to be induced by diverse pathogens, suggesting that Agrobacterium has co-opted a plant defense response and that bacterial VirF and plant VBF both contribute to targeted proteolysis that promotes plant genetic transformation.