| Kentucky Bluegrass(Poa pratensis) is a perennial herbal plant that belongs to the Poaceae family. It has great regeneration ability, good wear tolerance and stress tolerance, long green period and good tolerance to low mowing. In cool and moist climates areas, it is widely used in public green areas and sports grounds. With the exacerbation of global warming, scientists throughout the world pay more attention to the effect of heat stress on plant, especially for cash crops. It has become an urgent task to investigate molecular mechanism of heat-tolerance with heat-tolerant species or cultivars. With proteomic and metabolomic methods, different protein expression and metabolite accumulation related with heat stress in leaves and roots of Kentucky Bluegrass genotypes heat-tolerant ‘Midnight’ and heat sensitive ‘Briliant’ were analyzed in our paper. Results could be important for analyzing heat-tolerant mechanism in Kentucky bluegrass in the future. The main results were as follows:1. Plants of Kentucky Bluegrass genotypes ‘Midnignt’ and ‘Brilinant’ were exposed to heat stress in growth chambers for 28 d. Leave photochemical efficiency(Fv/Fm), electrolyte leakage(EL) of leaves and roots were analyzed every 7 d. Fv/Fm decreased significantly for two Kentucky bluegrass genotypes under heat stress. At long-term heat stress, EL of leaves and roots decreased. And compared with leaves, the effects of heat stress on EL of roots were more severe. It was found that the extent of changes in Fv/Fm and EL of leaves and roots for ‘Brilliant’ was more pronounced than those for ‘Midnight’.Total soluble proteins of leaves and roots were extracted from control treatment and heat-stressed plants, and separated by two-dimensional gel electrophoresis. 37 differentially expressed proteins were identified in leaves. 16 proteins were up-regulated, 12 proteins down-regulated in ‘Midnight’ and 8 proteins up-regulated and 8 proteins down-regulated in ‘Brilliant’. 28 differentially expressed proteins were identified in roots. Among them, 10 proteins were up-regulated, 2 proteins down-regulated in ‘Midnight’ and 15 proteins up-regulated and 8 proteins down-regulated in ‘Brilliant’. Founctional analysis of heat-responsive proteins between two cultivars suggested that the superior heattolrance in ‘Midnight” could be associated with high abundance of proteins involved in amino acid synthase in leaves and antioxidant enzymes and small molecular heat shock protein in roots.2. Related physiological index and metabolite accumulations were analyzed at 0 d, 7 d and 28 d under heat stress with two Kentucky Bluegrass genotypes heat-tolerant ‘Midnight’ and heat-sensitive ‘Briliant’. It was found that compared with 7 d of heat stress, the effects on physiological index was more pronounced at 28 d of heat stress. 76 and 82 metabolites were identified with gas chromatography-mass spectrometry analysis in leaves and root, respectively. These compounds include amino acids, amino acids, sugar and sugar alcohols and polyamines. The differential metabolic accumulation pattern at 7 d and 28 d of heat stress between two cultivars differing in heat tolerance demonstrated that the superior heat tolerance in ‘Midnight’ could be related to the accumulation of a series of metabolites, including pyruvic acid, butanedioic acid, glyceric acid, 2-ketoglutaric acid, gluconic acid, citric acid, isocitric acid, sucrose, galactinol, cysteine, valine, isoleucine, phenylalanine, ascorbic acid, glycerol, mannitol, myo-inositol, propylamine and cadaverine, etc. These metabolites could be related with heat-tolerant of heat-tolerant Kentucky bluegrass genotypes by protecting integrality of cell membrane, accelerating signal transduction, strengthening antioxidant capacity, osmotic regulation and detoxifying function in plant cell. |
PDF Full Text Request