THE PLANT CELL, Vol 9, Issue 12 2135-2142, Copyright © 1997 by American Society of Plant Biologists
Transfer and Integration of T-DNA without Cell Injury in the Host Plant
J. Escudero and B. Hohn
Friedrich Miescher-Institut, Postfach 2543, CH-4002 Basel, Switzerland
Agrobacterium colonizes plant cells via a gene transfer mechanism that
results in plant tumorigenesis. Virulence (vir) genes are transcriptionally
activated in the bacteria by plant metabolites released from the wound
site. Hence, it is believed that agrobacteria use injuries to facilitate
their entrance into the host plant and that the wounded state is required
for plant cell competence for Agrobacterium-mediated gene delivery.
However, our experiments using vir gene-activated bacteria sprayed onto
tobacco plantlets demonstrated that cells in unwounded plants could also be
efficiently transformed. The condition of the plant cells was monitored
using [beta]-glucuronidase under the control of a wound-inducible promoter.
Infection of leaf tissue is light dependent, and it is drastically reduced
when abscisic acid is exogenously applied to the plant. Under these
experimental conditions, stomatal opening seems to be used by Agrobacterium
to circumvent the physical barrier of the cuticle. These results thus show
that the proposed cellular responses evoked by wounding in higher plants
are not essential for Agrobacterium-mediated transformation.
