Stimulatory effect of copper and zinc sulphate on plant regeneration, glutathione- S -transferase analysis and assessment of antioxidant activities in Mucuna pruriens L. (DC)

The effect of heavy metals, CuSO4 and ZnSO4 on morphogenic response of cotyledonary node explants of Mucuna pruriens (L.), a fast growing tropical medicinal legume was evaluated. The climber holds economic importance in traditional as well as modern pharmaceutical areas. Murashige and Skoog (Physiol Plant 15:473–497, 1962) medium supplemented with various strength (0.5, 2.5, 4.5, 6.5 or 8.5 µM) of BA (6-benzyladenine), Kn (Kinetin) and 2-iP (2-isopentenyl adenine) were screened to establish optimum culture conditions for in vitro regeneration using cotyledonary node explant. Optimized medium (MS + BA 2.5 µM) was augmented with different concentration of CuSO4 (0.5–25.0 µM) and ZnSO4 (5–150 µM) to evaluate the effect of heavy metals on regeneration potential of the explants. Among various concentrations tested, MS medium with optimized BA (2.5 µM) along with 5.0 µM CuSO4 or 80.0 µM ZnSO4 proved beneficial, inducing 11.20 and 13.40 shoots per explant, respectively. The results demonstrated that glutathione-S-transferase (GSTs) was involved in fighting heavy metal stress, and might also have a role in in vitro regeneration. Elongated healthy microshoots on transfer to half strength MS medium produced 3.40 roots per shoot after 28 days of incubation without the necessity of exogenous auxin. The in vitro grown regenerants were hardened in Soilrite, and then established in garden and sandy soil (1:1) under natural light where they showed normal growth and development. The work highlights the enhanced multiplication and better growth of the regenerants using elevated concentration of CuSO4 and ZnSO4. GSTs overexpression activity not only confers to overcome the stress but enhanced the in vitro regeneration of M. pruriens also.