title: The limited host range of an Agrobacterium tumefaciens strain extended by a cytokinin gene from a wide host range T-region.
abstract: The host range of Agrobacterium tumefaciens strain LBA649 (pTiAg57) is limited to grapevine and a few other plant species. Its host range was extended through the introduction of the T-region from the wide host range octopine plasmid pTiAch5. In contrast, R prime plasmids harboring the entire wide host range virulence region were unable to achieve this effect. Via site-directed mutagenesis a search was performed to identify the T-DNA genes which were responsible for the observed host range extension. Inactivation of one of the onc-genes (the cyt gene) was found to abolish the capacity of the T-region to extend the host range of LBA649. Therefore, we cloned the cyt gene into a disarmed T-region plant vector and used it in complementation studies with pTiAg57 via the binary vector strategy. We show that the mere presence of the cyt gene from a wide host range Ti plasmid is sufficient to extend the host range of LBA649 to certain plants. We conclude that the limited host range of LBA649 is not caused by a lack of recognition of plants but is mainly due to the absence or inactivity of a cyt gene in the T-region of pTiAg57.
authors.affiliation: MOLBAS Research Group, Department of Plant Molecular Biology, University of Leiden, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Hoekema
authors.forename: B S
authors.initials: BS
authors.lastname: de Pater
authors.forename: A J
authors.initials: AJ
authors.lastname: Fellinger
authors.forename: P J
authors.initials: PJ
authors.lastname: Hooykaas
authors.forename: R A
authors.initials: RA
authors.lastname: Schilperoort