Heat exposure alters the expression of SOD, POD, APX and CAT isozymes and mitigates low cadmium toxicity in seedlings of sensitive and tolerant rice cultivars.
A 0-500 μM Cd(2+) alone and/or heat stress in rice cv. DR-92 (sensitive) and cv. Bh-1 (tolerant), altered the banding patterns of SOD, CAT, POD and APX enzymes in roots/shoots. In controls, six/seven activity bands for POD in roots/shoots were observed. The band intensities of some decreased under combination of Cd(2+) + heat stress. Six SOD isoforms in shoots of cv. Bh-1 and three in cv. DR-92 appeared. In sensitive cv. DR-92 a trinuclear Cu/Zn/Mn-SOD 1 isozyme was upregulated in shoots under Cd/HS/Cd + HS treatments whereas a suppression in the same was noticed in roots. Under Cd alone the Cu/Zn/Mn-SOD 2 was strongly induced in roots which was otherwise absent in all HS treatments. POD R7 band was absent in HS alone but was induced under Cd(2+) + HS treatments in rice cv. DR-92. In tolerant cv. Bh-1, isozyme Mn-SOD 3 was induced under Cd alone but was absent under HS. Cu/Zn/Mn-SOD 2 and Cu/Zn/Mn-SOD 3 were strongly induced in roots and shoots under low or moderate Cd(2+) + HS treatments. APX R4/CATR2 isozymes which were absent under Cd(2+) alone or HS alone were induced under combination of Cd(2+) + HS indicating de novo synthesis of enzyme proteins under combined stressors. Decreased band intensities under Cd(2+) + HS suggest a cross-talk between response pathways of Cd(2+) and heat stress in rice. Results suggest Cd(2+) specific, heat-specific, tissue specific and differential expression of SOD/POD/APX/CAT and that Mn-SOD 3/APXR4/CATR2 seem to form important components of antioxidant defense in rice roots under combination of Cd(2+) + HS which helps to mitigate the effect of low Cd(2+) toxicity in tolerant rice cv. Bh-1.
Institute of Environment and Sustainable Development, Banaras Hindu University, Varanasi 221005, India. kshah.iesdbhu@sify.com
Kavita
K
Shah
Sareeta
S
Nahakpam
D000975:Antioxidants / Q000378:metabolism; D060387:Ascorbate Peroxidases / Q000378:metabolism*; D002104:Cadmium / Q000633:toxicity*; D002374:Catalase / Q000378:metabolism*; D006358:Hot Temperature; D007527:Isoenzymes / Q000378:metabolism*; D012275:Oryza / Q000187:drug effects / Q000378:metabolism*; D009195:Peroxidase / Q000378:metabolism*; D036226:Seedlings / Q000187:drug effects / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism*
D000975:Antioxidants; D007527:Isoenzymes; D002104:Cadmium; C121048:guaiacol peroxidase; D060387:Ascorbate Peroxidases; D002374:Catalase; D009195:Peroxidase; D013482:Superoxide Dismutase