Development of efficient Agrobacterium rhizogenes-mediated hairy root system in Curcuma longa L. and elicitation driven enhanced production of pharmaceutically important curcuminoids

The Agrobacterium rhizogenes-mediated transformation of plants for hairy root induction epitomizes an attractive biotechnological strategy for enhancing the production of bioactive compounds from medicinal plants. The Curcuma longa L. (turmeric) belonging to Zingiberaceae family is a prevalent crop grown in India and other Southeast Asian countries. The three curcuminoids, viz. curcumin (CUR), demethoxycurcumin (DMC), and bisdemethoxycurcumin (BDMC), are the key bioactive components attributing to its pharmacological activity. The Curcuma longa hairy root lines were established from shoot base explants of in vitro grown plants using the A. rhizogenes strains A4, A4T, and 8196. The acetosyringone augmentation in bacterial culture and co-cultivation media proved to be advantageous for effective induction of hairy roots. The hairy root lines induced with A4 strain displayed maximum biomass growth after 25 days of inoculation, followed by 8196 and A4T. The transgenic nature of hairy roots was validated by the presence of rol A and mas1 gene. The maximum curcuminoid production was observed with hairy roots induced with A4 strain. The influence of methyl jasmonate (MJ) elicitor treatment was evaluated on growth and curcuminoid production using A4-induced hairy root lines. The MJ had very little influence on growth of hairy roots; however, higher concentrations of MJ (200 µM) evoked a significant response after 48 h for enhancing the production of all the three curcuminoids. The CUR content was 2.5-fold; DMC twofold; and BDMC 1.96-fold higher than unelicited hairy roots. Our results establish that the hairy roots of C. longa could be a stable potential source for pharmaceutically useful curcuminoids as an alternative to field-grown plants.