Molecular and biochemical response of Cannabis sativa plant to cadmium stress and the role of molybdenum

Abstract

Abstract Plants respond to heavy metals stress by the activation of stress responsive genes to establish biochemical defense mechanisms against the stress. We have investigated the molecular and biochemical response of Cannabis sativa to cadmium (Cd) stress in the presence of molybdenum (Mo) foliar treatments. Various parameters were inter-correlated i.e., Plant biomass, Cd phyto-accumulation, transcript level/expression of CBF/DREB genes, concentrations of free proline, polyphenolics and chlorophyll contents. Phenolic compounds were analyzed by High Performance Liquid Chromatography Diode Array Detector (HPLC-DAD) and Cd contents were analyzed by Atomic Absorption Spectrophotometer. Biomass and chlorophyll contents decreased while the concentrations of free proline and polyphenolics increased under Cd stress. Dry biomass of the all the plant tissues and free proline in roots and leaves were most significantly increased with foliar spray of 2.00 ppm Mo. Nineteen (19) different polyphenolic compounds were identified and quantified in leaves and most of them were highly increased in concentration under Cd stress. The highest concentration was noted in Caffeoyl tyramine (1111 µg/g) in 2.00 ppm Mo treated plants. Transcript level of CBF/DREB genes were less as compared to Mo treated plants, where a high increase in transcript level of these genes were found. Expression of CBF /DREB genes showed significant positive correlations with dry-biomass, Cd accumulation and concentrations of free proline and polyphenolics in leaves. The results suggested that Mo increased the expression of CBF/DREB genes and subsequently the concentration of phenolic compounds and free proline under Cd stress.