RolB expression pattern in the early stages of carrot somatic embryogenesis.

The pattern of expression of the rolB gene, derived from the T-DNA of the plant pathogen Agrobacterium rhizogenes, has been investigated during the early stages of somatic embryo formation in suspension cultures of carrot (Daucus carota L.). The reporter gene GUS (Escherichia coli beta-glucuronidase), under transcriptional control of full-length rolB promoter region, has been utilized in order to evaluate both qualitative and quantitative variations in the expression pattern. Fluorimetric measurements point to the developmental regulation of the gene, while results from histochemical analysis indicate that the promoter of rolB is firstly activated in the central (core) region of the globular embryos.