Monday, November 13, 2006 - 2:30 PM

The Role of Proteins in the Freeze Tolerance of Zoysiagrass.

Aaron Patton and Zac Reicher. Purdue University, 915 West State Street, West Lafayette, IN 47907-2054

There are considerable differences in the winter survival of zoysiagrass species [Zoysia japonica Steud. and Z. matrella var. matrella (L.) Merr.] and cultivars, but the physiological basis for these differences has only partially been explored. Our objective was to determine the relationship between protein levels with the acclimation status and freeze tolerance of zoysiagrass. Thirteen cultivars of zoysiagrass were selected with contrasting cold hardiness. Cold-acclimation was induced with four weeks of 8/2°C day/night cycles and a 10-h photoperiod of 300 μmol m-2 s-1. Proteins were quantified using SDS-PAGE and immunoblotting with a rabbit anti-dehydrin polyclonal antibody. Total protein concentration was higher among cold-acclimated plants (7.3 mg g-1 dry wt.) than non-acclimated (5.1 mg g-1 dry wt.). Though total protein concentration was similar across species, protein concentration varied among cultivars and ranged from 6.3 to 9.0 mg g-1 dry wt. in cold-acclimated plants. Polyacrylamide gels indicated that cultivar and acclimation did not significantly influence protein composition. Immunoblotting indicated that dehydrins (23 and 25 kDa) increase in response to cold acclimation. Optical density values for the 23 kDa dehydrin was positively correlated (r2 = 0.41) with low freezing tolerance. Our results suggest that dehydrins are associated with both cold-acclimation and freeze tolerance in zoysiagrass.