Arabidopsis F‐box proteins D5BF1 and D5BF2 negatively regulate Agrobacterium‐mediated transformation and tumorigenesis

The pathogen Agrobacterium tumefaciens is known for causing crown gall tumours in plants. However, it has also been harnessed as a valuable tool for plant genetic transformation. Apart from the T‐DNA, Agrobacterium also delivers at least five virulence proteins into the host plant cells, which are required for an efficient infection. One of these virulence proteins is VirD5. F‐box proteins, encoded in the host plant genome or the Ti plasmid, and the ubiquitin/26S proteasome system (UPS) also play an important role in facilitating Agrobacterium infection. Our study identified two Arabidopsis F‐box proteins, D5BF1 and D5BF2, that bind VirD5 and facilitate its degradation via the UPS. Additionally, we found that Agrobacterium partially suppresses the expression of D5BF1 and D5BF2. Lastly, stable transformation and tumorigenesis efficiency assays revealed that D5BF1 and D5BF2 negatively regulate the Agrobacterium infection process, showing that the plant F‐box proteins and UPS play a role in defending against Agrobacterium infection. D5BF1 and D5BF2 suppress the Agrobacterium infection process by mediating the degradation of Agrobacterium virulence protein VirD5 through the host's ubiquitin/26S proteasome system.