It is a part of Ti Plasmid which takes part intransfer and integration of T-DNA into plant chromosome. The vir sequence consist of 8 operons which take part in different functions associated with virulence of Ti Plasmid. These are vir H, vir A, vir B, vir G, vir C, vir D, vir E, & vir F. ( vir H & vir F present occasionally).