Virulence genes A, G, and D mediate the double-stranded border cleavage of T-DNA from the Agrobacterium Ti plasmid.
Agrobacterium tumefaciens transfers the T-DNA portion of its Ti plasmid to the nuclear genome of plant cells. Upon cocultivation of A. tumefaciens strain A348 with regenerating tobacco leaf protoplasts, restriction endonuclease fragments of the T-DNA were generated that are consistent with double-stranded cleavage of the T-DNA at the border sequences. The T-DNA border cleavage was also induced by acetosyringone, a compound that induces many of the virulence genes. T-DNA cleavage did not occur in Agrobacterium strains harboring Tn3-HoHo1 insertions in the virA, -D, or -G genes. Insertion mutations in virB, -C, or -E did not have any effect on the T-DNA cleavage. Complementation of the mutations in virA, -D, or -G with cosmids containing the respective wild-type genes restored the T-DNA cleavage. Since virA and -G are essential in regulating the expression of other vir genes in response to plant signal molecules, the virD gene product(s) appear to mediate double-stranded T-DNA border cleavage.
Veluthambi
K
K
Department of Biological Sciences, Lilly Hall of Life Sciences, Purdue University, West Lafayette, IN 47907.
Jayaswal
R K
RK
Gelvin
S B
SB