Coronatine alleviates polyethylene glycol-induced water stress in two rice (Oryza sativa L.) cultivars

We studied the effects of coronatine (COR), a structural and functional analogue of jasmonates, on the drought tolerance of two rice cultivars, Handao 297 (a drought-tolerant upland rice) and Yuefu (a drought-sensitive lowland rice). Seedlings were treated with COR at the three-leaved stage at 0.01 and 0.1 mu(M) for 24 h, followed by imposition of water deficit induced with 20 % polyethylene glycol (PEG). Water stress reduced the biomass of both cultivars and increased leaf lipid peroxidation and solute leakage. Pre-treatment with COR significantly increased the activities of superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase in leaf tissues of water-stressed Handao 297 (0.01 mu(M) and Yuefu (0.1 mu(M)) seedlings. COR supplement also increased the accumulation of 44 and 32 kDa polypeptides in water-stressed Handao 297 (0.01 and 0.1 mu(M)) and Yuefu (0.1 mu(M)) and significantly induced the expression of 29 kDa polypeptide in Handao 297. The results suggest that COR might alleviate drought stress by activating antioxidant enzymes and inducing proteins, thereby preventing membrane peroxidation and denaturation of bio-molecules. Thus, membrane permeability decreased substantially by 24-27 % in Handao 297, and 22-29 % in Yuefu. The optimal concentrations conferring drought resistance were 0.01 for the upland rice and 0.1 mu(M) for the lowland cultivar.