Stimulation of Agrobacterium tumefaciens T-DNA transfer by overdrive depends on a flanking sequence but not on helical position with respect to the border repeat.

T-DNA transfer by Agrobacterium tumefaciens depends on the right border repeat of the T-DNA and is greatly stimulated by overdrive, an adjacent sequence. We report that the function of overdrive does not depend on helical position with respect to the border repeat. A synthetic 24-bp overdrive and a 12-bp region containing a fully conserved 8-bp core overdrive sequence stimulated virulence equally, but full function required additional bases to the left of the 24-bp sequence.