A CARROT LEUCINE-RICH-REPEAT PROTEIN THAT INHIBITS ICE RECRYSTALLIZATION

Many organisms adapted to live at subzero temperatures express antifre eze proteins that improve their tolerance to freezing. Although struct urally diverse, all antifreeze proteins interact with ice surfaces, de press the freezing temperature of aqueous solutions, and inhibit ice c rystal growth. A protein purified from carrot shares these functional features with antifreeze proteins of fish. Expression of the carrot co mplementary DNA in tobacco resulted in the accumulation of antifreeze activity in the apoplast of plants grown at greenhouse temperatures. T he sequence of carrot antifreeze protein is similar to that of polygal acturonase inhibitor proteins and contains leucine-rich repeats.