Mechanism of action of hydrogen peroxide in wheat thermotolerance - interaction between antioxidant isoenzymes, proline and cell membrane

Abstract

Terminal heat stress causes an array of physiological, biochemical and morphological changes in plants, which affect plant growth and development. It has very severe effect on the pollen viability and seed setting in wheat. In the present investigation, an altered expression of H₂O₂ (0.9 μg/g in C-306 and 0.75 μg/g in HD2329) was observed with the highest accumulation at seed hardening stage and against heat shock (HS) of 42°C for 2 h. With the increase in H₂O₂ accumulation, an increase in the number of isoenzymes of superoxide dismutase and catalase were observed with high activities under differential heat shock. A decrease in the proline accumulation was observed under differential heat shock. Exogenous application of H₂O₂ (10 mmole/L) leads to increase in the accumulation of intracellular H₂O₂ and further an increase in the number of isoenzymes of superoxide dismutase (SOD) and catalase (CAT) was observed. The tolerant cultivar was more responsive to exogenous application of H₂O₂ compared to susceptible cultivar. The percentage decrease in cell membrane stability under differential heat shock was low in H2O2 treated plants compared to non-treated. The results from this study suggest a potential role for H₂O₂ in regulating the activity of antioxidant enzymes and accumulation of proline inside cells and in turn influence the cell membrane stability under heat stress. All the defense associated genes were observed to be very responsive to intracellular H₂O₂, which gives inference that H₂O₂ has regulatory role to play in controlling the expression and activities of these proteins under abiotic stresses.

Key words: Antioxidant enzymes, wheat, heat stress, H₂O₂, proline, catalase, superoxide dismutase, cell membrane stability, reactive oxygen species.