Impact of calcium on ascorbate-glutathione pool and gene expression under cadmium stress in Indian mustard (Brassica juncea L.)

Abstract

A screen house study was designed to elucidate whether exogenously applied calcium (Ca1; 25 mM, Ca2; 50 mM) alleviate cadmium (Cd)-induced (Cd1; 200 ppm, Cd2; 400 ppm and Cd3; 600 ppm Cd) stress in Brassica juncea (RH 725). To study this effect, antioxidants enzymes involved in ascorbate-glutathione cycle (catalase (CAT), glutathione reductase (GR), ascorbate (Asc) and glutathione (GSH)) were studied in leaf tissue of mustard at three development stages (30, 60 and 90 days after sowing (DAS)). Cadmium treatment (Cd3) reduced plant growth by accumulating hydrogen peroxide and malondialdehyde of 203, 156 and 161 % and 41.3, 34 and 21.5 % at 30-, 60- and 90-days plant respectively. In response to this, antioxidative enzymes like CAT and GR increased by 20.5 and 90 % at 90 days and ameliorated oxidative stress. Exogenous calcium administration of 50 mM maintained the cell's redox state by enhancing enzyme activity and maintaining cellular homeostasis. GSH (19 %) and Asc (14 %) contents increased under Cd stress and played major in reducing the stress. Yield decreased greatly under Cd stress, but calcium application revived the antioxidants and improved yield and oil content. Besides, differential fold gene expression level of BjCd1, BjCaT, BjSOD and BjGR1 exhibited slight increase under Cd stress. Furthermore, calcium administration to stressed plants favourably affected the expression, aiding in stress resistance. Overall, our data show that calcium protect cadmium stressed Brassica plants from yield loss, suggesting that calcium might be an excellent substitute for lowering cadmium toxicity in crops.