Bidirectional transfer from a 24 bp border repeat of Agrobacterium tumefaciens

T-region transfer from wild-type Agrobacterium strains is thought to be an orientated process, starting at the right border repeat and terminating at the left border repeat of the T-region. Here we demonstrate that a right border repeat in the inverted orientation relative to the onc-genes can also mediate transfer of the T-region to the plant cell, although with lower efficiency as a border repeat in the native orientation. Transfer mediated by an inverted right border repeat is stimulated by the presence of the T-region transfer enhancer. Similar single stranded molecules, comprising the bottom strand of the T-DNA, were isolated from acetosyringone induced bacteria, irrespective of the orientation of the right border. These findings show that border repeats work bidirectionally to some extent.