Thermal hysteresis antifreeze proteins have been well studied in animals, especially marine teleost fishes and terrestrial arthropods, and recently thermal hysteresis proteins were reported in several plants, all angiosperms, collected in winter. This study shows for the first time that thermal hysteresis protein activity is also present in nonangiosperm plants, fungi, and bacteria.
In addition to six species of angiosperms (Dicentra cucularia, Dutchman's breeches, tubers; Daucus carota, carrot, both cultivated and wild; Hemerocallis fulva, day-dily, bulbs; Populus deltoides, eastern cottonwood; Quercus alba, white oak, acorns; and Triticum aestivum, winter wheat), thermal hysteresis activity (THA) was demonstrated in the evergreen Christmas fern (Polystichum acrostichoides), a horsetail (Equisetum hymenale), a club moss (Lycopodium dendroideum), the ginko tree (Gynko biloba), and three mosses (Mnium cuspidatum, Polytrichum ohioense and Brachythecium salcbrosum). Thus, THA is present in phylogenetically diverse plants. Thermal hysteresis protein activity was also identified for the first time in two additional kingdoms, the fungi and bacteria. Fungi included fruiting bodies of the winter mushroom (Flammulina velupites) and the oyster mushroom (Pleurotus ostreatus) and two bracket fungi (Coriolus versicolor and a Stereum sp.). In addition, two bacteria (Rhodococus erythropolis and Micrococcus cryophilus) acclimated at 3°C had THA. In plants and fungi THA was only present during winter and in bacteria when cold acclimated. Treatment of samples of certain of these organisms with protease eliminated the THA, demonstrating that the activity was due to the presence of thermal hysteresis proteins.
