Improved Heat Tolerance through Drought Preconditioning Associated with Changes in Lipid Composition, Antioxidant Enzymes, and Protein Expression in Kentucky Bluegrass
2012
Peng, Yan | Xu, Chenping | Xu, Lixin | Huang, Bingru
Plant tolerance to drought and heat stress may be interrelated. The study was designed to examine whether improved heat tolerance through drought preconditioning is associated with changes in lipid and protein content and antioxidant enzyme activities. Kentucky bluegrass (Poa pratensis L.) (cv. Brilliant) plants were well watered (non-preconditioned control) or exposed to drought without irrigation for 12 d (drought preconditioning) and then exposed to heat stress (35°C/30°C) for 25 d in growth chambers. Compared to the non-preconditioned control, preconditioned plants had higher turf quality and chlorophyll content, and lower leaf electrolyte leakage and lipid peroxidation under heat stress. Lipid saturation level increased under heat stress due to decreases in the content of linolenic (C18:3) and increases in linoleic (C18:2) and palmitic (C16:0) acids. Total fatty acid content and the content of C18:3 were significantly higher and C16:0 content was lower in preconditioned than in non-preconditioned plants at 15 d of heat stress. The activity of superoxide dismutase increased in preconditioned plants at the initiation of heat stress, but it decreased in non-preconditioned plants under heat stress. Preconditioned plants had higher catalase and ascorbate peroxidase activities than non-preconditioned plants under heat stress. Drought preconditioning accelerated the up-regulation of chaperonin and heat shock protein 90, inhibited the down-regulation of proteins for amino acid metabolism, and induced the expression of lipoxygenase. These results imply that drought-preconditioning-enhanced heat tolerance was associated with the promotion of antioxidant activities and chaperoning protein expression, protecting plants from cellular damages from heat stress.
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