Cell commitment and rolB gene expression in the induction of root differentiation

The relative role played in the induction of root differentiation by the morphogenetic gene rolB, present in the T-DNA of Agrobacterium rhizogenes, and the specific commitment of different plant cell types, has been evaluated by means of an in vitro-rooting assay. Explants of different origin derived from transgenic tobacco plants transformed by both the rolB gene and the GUS reporter gene (E. coli P-glucuronidase) under the transcriptional control of rolB promoter region were utilized and compared to control transformants containing only the rolB-GUS construct. The results obtained demonstrate that: the pattern of gene expression is similar in both transformants; rolB - containing tissues are far more effective than untransformed and GUS-transformed controls in regenerating roots; the presence and expression of rolB are necessary but not sufficient to trigger rhizogenesis in transformed plant cells.