The effects of rol genes of Agrobacterium rhizogenes on morphogenesis and secondary metabolite accumulation in medicinal plants

Abstract

Induction of hairy roots by Agrobacterium rhizogenes and regeneration of Ri-transformed plants from such transgenic roots are reported in a large number of taxonomically diverse plant species. Ri-transformed cultures (roots/calli/plants) have altered characteristics of their own compared to non-transformed ones. Four rol genes (rolA, rolB, rolC, rolD) of T-DNA of Ri-plasmid are known to be responsible for these phenomena. However, few attempts have been made to elucidate the role of individual rol genes on morphogenic ability. In addition, the effect of wild-type A. rhizogenes on the production of secondary metabolites is well studied in wide number of plant species. The popularity of this research has never declined through time which explains its immense value and provides a hope for a promising future. Based on such studies, several reviews have been written from time to time, explaining the ‘rol effect’ on secondary metabolite accumulation in medicinal plants and to discuss the advances in this field of research. However, investigations dealing with the effect of individual rol genes are comparatively less and need further attention. Therefore, in this chapter, we have discussed in detail the effects of each of the four rol genes individually or in combination on in vitro morphogenesis and secondary metabolite accumulation in medicinal plants.