Enhanced secondary metabolite production and pathway gene expression by leaf explants-induced direct root morphotypes are regulated by combination of growth regulators and culture conditions in Centella asiatica (L.) urban

Abstract

Centella asiatica (L), a herbaceous plant belonging to the family Apiaceae, possesses great medicinal value owing to the presence of important and characteristic triterpenoids as secondary metabolites. These triterpenoid secondary metabolites are found in leaves in substantial quantities whereas negligible amounts may be detected sometimes in root tissues. In the resent study direct rhizogenesis was induced from C. asiatica leaf explants using different concentrations and combinations of auxins (IBA/IAA/NAA) leading to the production of distinct root morphotypes. A number of culture conditions such as pH, nature of carbon sources (glucose, fructose, mannitol and maltose) as well as concentrations of sucrose exhibited their strong influence in terms of induction of root morphotypes, accumulation of total secondary metabolites and expression of key pathway genes. Phytochemical profiling using HPLC revealed that all root morphotypes accumulated enhanced amounts of triterpenoids. The enhanced phytochemical accumulation was further validated by the coherent pattern of expression of key genes related to their biosynthetic pathway in root morphotypes. The results have revealed that the hormonal combinations in the culture media not only mediated differential morphogenic responses but also regulated secondary metabolites accumulation in non-transgenic rhizogenic roots. The results of the study are promising for the utilization of such in vitro root morphotypes. The root morphotypes may act as alternative bioresources for the production of industrially important and leaf associated asiaticosides and other important triterpenoids for the commercial purposes.