Bacterial conjugation protein MobA mediates integration of complex DNA structures into plant cells

Agrobacteritum tumefaciens transfers T-DNA to plant cells, where it integra tes into the genome, a property that is ensured by bacterial proteins VirD2 and VirE2. Under natural conditions, the protein MobA mobilizes its encodi ng plasmid, RSF1010, between different bacteria. A detailed analysis of Mob A-mediated DNA mobilization by Agrobacterium to plants was performed. We co mpared the ability of MobA to transfer DNA and integrate it into the plant genome to that of pilot protein VirD2. MobA was found to be about 100-fold less efficient than VirD2 in conducting the DNA from the pTi plasmid to the plant cell nucleus. However, interestingly, DNAs transferred by the two pr oteins were integrated into the plant cell genome with similar efficiencies . In contrast, most of the integrated DNA copies transferred from a MobA-co ntaining strain were truncated at the 5' end. Isolation and analysis of the must conserved 5' ends revealed patterns which resulted from the illegitim ate integration of one transferred DNA within another. These complex integr ation patterns indicate a specific deficiency in MobA. The data conform to a model according to which efficiency of T-DNA integration is determined by plant enzymes and integrity is determined by bacterial proteins.