Recovery of Agrobacterium tumefaciens T-DNA molecules from whole plants early after transfer.

A system for the analysis of independent T-DNA transfer events from Agrobacterium to plants is described. The complete T-DNA except for the 25 bp border sequences was replaced by one genome of a plant virus so that upon transfer to the plant, a viable replicon is produced by circularization. Rescue of virus from such infected plants allowed analysis of DNA sequences at or close to the ends of T-DNA molecules. A rather conserved right border remnant of three nucleotides was found, whereas the sequences remaining at the left end were more variable. A point deletion in the left 25 bp sequence results in even less precise processing at the left end. In addition, many rescued T-DNA molecules carry small direct repeats between the joined T-DNA ends; linear T-DNA molecules are therefore transported to the plant.