A carrot leucine-rich-repeat protein that inhibits ice recrystallization

Many organisms adapted to live at subzero temperatures express antifreeze proteins that improve their tolerance to freezing. Although structurally diverse, all antifreeze proteins interact with ice surfaces, depress the freezing temperature of aqueous solutions, and inhibit ice crystal growth. A protein purified from carrot shares these functional features with antifreeze proteins of fish. Expression of the carrot complementary DNA in tobacco resulted in the accumulation of antifreeze activity in the apoplast of plants grown at greenhouse temperatures. The sequence of carrot antifreeze protein is similar to that of polygalacturonase inhibitor proteins and contains leucine-rich repeats

Isolation and characterization of a novel antifreeze protein from carrot (Daucus carota)

A modified assay for inhibition of ice recrystallization which allows unequivocal identification of activity in plant extracts is described. Using this assay a novel, cold-induced, 36 kDa antifreeze protein has been isolated from the tap root of cold-acclimated carrot (Daucus carota) plants, This protein inhibits the recrystallization of ice and exhibits thermal-hysteresis activity. The polypeptide behaves as monomer in solution and is N- glycosylated, The corresponding gene is unique in the carrot genome and induced by cold, The antifreeze protein appears to be localized within the apoplast