Nucleic Acids Research

T-region transfer from wild-type Agrobacterlura 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 one-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-reglon transfer enhancer. Similar single 3tranded 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 bidirectlonally to some extent.