Identification of proteins associated with water-deficit tolerance in C4 perennial grass species, Cynodon dactylon×Cynodon transvaalensis and Cynodon dactylon.

The study was conducted to examine differential proteomic responses to water-deficit stress in hybrid bermudagrass [Cynodon dactylon (L.) Pers. ×Cynodon transvaalensis Burtt Davy, cv. Tifway] and common bermudagrass (C. dactylon, cv. C299). Plants were exposed to water-deficit stress for 15 days by withholding irrigation in a growth chamber. Leaf electrolyte leakage increased and photochemical efficiency and relative water content declined under water-deficit stress, but the extent of changes in each of the physiological parameters for 'Tifway' was less pronounced than those for 'C299'. Total proteins of leaves were extracted from well-watered and water-deficit plants and separated by two-dimensional gel electrophoresis. Of the 750 protein spots reproducibly detected, 32 proteins had increases in the abundance and 22 proteins exhibited decreases in the abundance in at least one genotype under water-deficit stress. A significantly higher number of proteins were found to accumulate in 'Tifway' than in 'C299' and 16 proteins with increasing abundance were detected only in 'Tifway' under water-deficit stress. All stress-responsive proteins were subjected to mass spectrometry analysis, which were mainly involved in metabolism, energy, cell growth/division, protein synthesis and stress defense. Functional analysis of differential drought-responsive proteins between the two genotypes suggests that the superior water-deficit tolerance in 'Tifway' bermudagrass could be mainly associated with less severe decline in the abundance level of proteins involved in photosynthesis (chlorophyll a-b, ATP synthase subunit alpha, phosphoribulokinase and ribulose-1,5-bisphosphate carboxylase/oxygenase) and greater increase in the abundance level of antioxidant defense proteins (superoxide dismutase, ascorbate peroxidase, dehydroascorbate reductase and peroxiredoxin), demonstrating that maintaining photosynthesis and active antioxidant defense mechanisms may play a critical role in C(4) grass adaptation to water-deficit stress.