Tissue culture of medicinal plants: Micropropagation, transformation and production of useful secondary metabolites

Abstract

Plant tissue culture studies were carried out for the preservation of medicinal plant resources and efficient production of pharmaceutically important secondary metabolites. Micropropagation methods for Cephaelis ipecacuanha were established and these methods enabled much more efficient propagation of plants than the conventional methods using seedling or layering. The C. ipecacuanha plants propagated through tissue culture grew uniformly in the field and they constituted relatively high alkaloid contents compared to the plants grown from seedling. Adventitious root cultures of Cephaelis ipecacuanha and Duboisia myoporoides-D. leichhardtii hybrid were grown. These root cultures produced sufficient amount of pharmaceutically important alkaloids (emetine and cephaeline in C. ipecacuanha ; scopolamine and hyoscyamine in Duboisia hybrid ) in MS liquid medium supplemented with IAA chloro-derivatives. The alkaloid yields from cultured roots of C. ipecacuanha , grown for seven weeks in 50 ml MS liquid medium containing 0.01 mg/l 5,6-Cl 2 -IAA are comparable to those from roots of a one-year-old plant cultivated in a greenhouse. Transformed cultures of Duboisia myoporoides-D. leichhardtii hybrid, Atropa belladonna , Cephaelis ipecacuanha , Digitalis lanata and Papaver somniferum have been established by infection with Agrobacterium rhizogenes , and the production of important pharmaceuticals of plant origin by these cultures was successfully demonstrated. In the case of Digitalis lanata hairy roots, it was elucidated that the greening of the roots under the light stimulated cardenolides formation. Transgenic plants were successfully obtained from the transformed cultures of Atropa belladonna , Cephaelis ipecacuanha and Papaver somniferum , in line with the molecular breeding of these plants using Agrobacterium rhizogenes . Furthermore, the production of low morphine Papaver somniferum plants, which mainly contain codeine, was first achieved by transformation of Agrobacterium rhizogenes .