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.