CELL COMMITMENT AND ROLB GENE-EXPRESSION IN THE INDUCTION OF ROOT DIFFERENTIATION

The relative role played in the induction of root differentiation by t he morphogenetic gene rolB, present in the T-DNA of Agrobacterium rhiz ogenes, and the specific commitment of different plant cell types, has been evaluated by means of an in vitro-rooting assay. Explants of dif ferent origin derived from transgenic tobacco plants transformed by bo th the rolB gene and the GUS reporter gene (E. coli P-glucuronidase) u nder the transcriptional control of rolB promoter region were utilized and compared to control transformants containing only the rolB-GUS co nstruct. The results obtained demonstrate that: the pattern of gene ex pression is similar in both transformants; rolB - containing tissues a re far more effective than untransformed and GUS-transformed controls in regenerating roots; the presence and expression of rolB are necessa ry but not sufficient to trigger rhizogenesis in transformed plant cel ls.