Proteomic Analysis of Cold Acclimation in Zoysiagrass.

Zoysiagrasses (Zoysia spp.) are warm season perennial turfgrasses primarily grown in the southern and transition zones of the United States. Varying levels of winter injury have been observed among zoysiagrass genotypes and cold-acclimation has been shown to have a significant effect on winter injury in these species. An understanding of the physiological changes that zoysiagrasses undergo during cold acclimation may shed light on phenotypic traits useful in selection of more cold tolerant varieties. To investigate the relationship between cold acclimation, protein expression, and freeze tolerance, crown tissues of freeze tolerant ‘Meyer’ and freeze susceptible ‘Victoria’ (Z. japonica Steud.) were harvested for proteomic analysis after a four week acclimation period. Additionally, cold-acclimated and non-acclimated cone-tainers of ‘Meyer’ and ‘Victoria’ were evaluated in four controlled freezing chambers reaching -6, -8, -10, and -12ºC to compare the impact of cold acclimated and non-acclimated treatments on freeze tolerance. Results of freeze testing indicated that cold acclimation has a significant influence on the freeze response of these cultivars. The interaction between cultivar and acclimation treatment was highly significant (p=0.0037). While significant differences in cultivar response were recorded for acclimated plants (p=0.0300), there were no significant differences among cultivars for non-acclimated plants (p>0.05). Proteomic analysis identified 9 and 23 unique protein spots for Meyer and Victoria, respectively, with increased abundance or decreased abundance in response to cold acclimation. In addition, we found 32 protein spots differentially expressed among the two cultivars in response to cold acclimation. These cold acclimation responsive proteins were identified for biological functions and found to be involved in carbohydrate, lipid, and amino acid metabolism, energy production, signal transduction and stress defense, which could contribute to the differences in freezing tolerance among the zoysiagrass cultivars evaluated in this study.