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Agrobacterium transfers T-DNA and effector proteins into plant cells. VirE2, one of these virulence effectors, enters the plant cell and is thought to bind T-strands. How VirE2 is trafficked inside the plant cell is not fully understood. Using bimolecular fluorescence complementation, in vitro pull-down, yeast two-hybrid, and in vivo co-immunoprecipitation assays, we found that VirE2 binds directly to the cargo binding domains of several myosin VIII family members, and to myosin XI-K. We observed reduced susceptibility of several Arabidopsis actin mutants and a myosin VIII-1/2/a/b mutant to transformation. Expression of cargo binding domains of myosin VIII-1, VIII-2, VIII-A, or VIII-B inhibits Arabidopsis root transformation. However, no myosin VIII protein contributes to the intracellular trafficking of VirE2. Expression of myosin VIII-2, -A, -B, but not VIII-1, cDNAs in the myosin VIII-1/2/a/b mutant partially restored transformation. Fluorescently-tagged VirE2 relocalized from the cellular periphery into the cytoplasm after delivery of T-strands from Agrobacterium. Mutation of myosin XI-k and expression of the myosin XI-K cargo binding domain had no effect on transformation but blocked VirE2 movement. Myosin VIII proteins may facilitate VirE2 tethering to the plasma membrane from which they bind incoming T-strands. Myosin XI-K is important for VirE2 movement through the cytoplasm.

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