Combined effect of cadmium toxicity and heat alter protein, lipid peroxidation and production of reactive oxygen species in growing rice seedlings of cvs. DR-92 and Bh-1

Abstract

Results suggest variation in stress response with the type of stress is given either singly or in combination of Cd2+ and heat to seedlings of rice cvs. DR-92 and Bh-1. Increased production of H2O2 and O2.- levels showed higher under combined stress. Elevated levels of TBARs indicated membrane damage in both roots and shoots. Maximum level of total soluble protein were noted under 100 I¼M Cd2+ + heat stress in cv. Bh-1 and in 500 I¼M Cd2+ + heat stress in cv. DR-92 at 15 day of growth. The study revealed an altered protein level under Cd2+ toxicity alone and Cd2+ + heat stress. Synthesis of stress specific LMW (20 to 60 kDa) and HMW ( 90 to 200 kDa) proteins under Cd2+, heat and Cd2+ + heat stress were recorded in both the rice cultivars. In cv. DR-92 five new protein bands (S1-S5) were present in shoots under 500 I¼M Cd2+ + heat treatments. In roots of cv. DR-92 two new protein bands R1 (HMW, ~90-100 kDa) and R2 (LMW, ~55-58 kDa) were present under 10 I¼M Cd2+ + heat treatments. The induction of both HMW and LMW and an increase in the intensity of already existing proteins under combined effect of Cd2+ and heat stress suggest the involvement of both constitutive and inducible cytosolic proteins in stress combating phenomenon. Of the two rice cultivars cv. Bh-1 appears to better adapted to Cd2+ stress alone as well as in combination with heat stress, than cv. DR-92.