Discovery of an antifreeze protein in the leaves of Ammopiptanthus nanus

Yu. S., Yin, L. and Mu, S. 2010. Discovery of an antifreeze protein in the leaves of Anitnopiptanthus nanus. Can. J. Plant Sci. 90: 35-40. Overwintering plants produce antifreeze proteins (AFPs) that allow plants to survive under freezing or subfreezing conditions. Ammopiptanthus nanus (M. Pop.) Cheng f. grows in the desert of Xinjiang., P.R. China, and our objective was to determine if its survival was dependent on AFP and to identify the protein. Using anion exchange and gel filtration, the AFP was extracted, isolated and purified from cold-acclimated A. nanus leaves. The thermal hysteresis activity (THA) of the antifreeze proteins was measured by differential scanning calorimetry. The THA of the AFP was 0.46 degrees C when the concentration of the protein was 20 mg mL(-1). The molecular weight of a band was about 119.24 kDa in SDS-PAGE gel. We detected (P < 0.05) the ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit by analyzing the 119.24 kDa protein using the Waters SYNAPT (TM) high definition mass spectrometry (HDMS (TM)) System. Our results indicate that there is an AFP in A. nanus leaves, and that it may play a vital role as a defence against the cold climate, thus increasing the chances for survival of A. nanus in its desert habitat.