Characterization of antifreeze activity in Antarctic plants

• Published in: Journal of experimental botany 2005-04, Vol.56 (414), p.1189-1196
• Main Authors: Bravo, León A, Griffith, Marilyn
• Format: Article
• Language: English
• Subjects: acclimation; Acclimatization; ambient temperature; Antarctic plants; Antarctic Regions; antifreeze activity; Antifreeze proteins; Antifreeze Proteins - physiology; Antifreezes; apoplastic proteins; Biological and medical sciences; Caryophyllaceae; Caryophyllaceae - physiology; cell walls; cold; cold acclimation; cold stress; Cold Temperature; cold tolerance; Colobanthus quitensis; Crystals; Deschampsia; Deschampsia antarctica; Enzymes; Freezing; freezing tolerance; Fundamental and applied biological sciences. Psychology; Ice; intercellular spaces; Leaves; Metabolism; molecular weight; plant adaptation; Plant Physiological Phenomena; Plant physiology and development; plant proteins; Plant Proteins - physiology; Plants; Poaceae - physiology; proteolysis; RESEARCH PAPER; seasonal variation; Vascular plants
• ISSN: 0022-0957; 1460-2431; 1460-2431
• DOI: 10.1093/jxb/eri112

Deschampsia antarctica and Colobanthus quitensis are the only vascular plants to have colonized the Maritime Antarctic, which is characterized by its permanently low temperature and frequent summer frosts. To understand how the plants survive freezing temperatures year-round, antifreeze activity was assayed in apoplastic extracts obtained from both non-acclimated and cold-acclimated Antarctic plants. By observing the shape of ice crystals grown in dilution series of the extracts, it was found that D. antarctica had antifreeze activity, but C. quitensis did not. D. antarctica exhibited antifreeze activity in the non-acclimated state and this activity increased after cold acclimation. The antifreeze activity in D. antarctica was labile to proteolysis and high temperature, active over a wide pH range, and associated with molecules greater than 10 kDa in molecular weight. These results show that D. antarctica produces antifreeze proteins that are secreted into the apoplast. When examined by SDS-PAGE, the apoplastic extracts from cold-acclimated D. antarctica exhibited 13 polypeptides. It is concluded that D. antarctica accumulates AFPs as part of its mechanism of freezing tolerance. Moreover, this is the first plant in which antifreeze activity has been observed to be constitutive.