Functional Characterization And Genetic Transformation Of Insect Antifreeze Protein Genes

Cold-adapted organisms have evolved several mechanisms to prevent potential cellular damage due to freezing. One such mechanism involves production of antifreeze proteins (AFPs, also known as thermal hysteresis proteins), which protects an organism from freezing at temperatures below 0℃. AFPs have been isolated from a number of fish and plants, and from insects. The proteins are thought to function by inhibiting the growth of small ice crystals, or by masking sites that could act as heterogeneous icenuclei. AFPs inhibit the growth of ice by adsorbing to the surface and forcing the ice to grow in curved fronts, which is an energetically unfavorable process; the melting point of ice, however, remains unaffected. The difference between the lowest temperature at which AFPs are able to prevent ice growth and the melting point of the solution is termed thermal hysteresis, and is used as a measurement of antifreeze activity.Studies on insect antifreeze proteins have focused on several species, so far over twenty antifreeze proteins had been isolated. scientists found that the highest thermal hysteresis activity (THA) tested for all AFPs is from insects, which is 10～100 times higher than the fish AFPs and much higher than plant AFPs . Therefore the insect antifreeze protein might be fully applied to many fields such as the low temperature storage, organ cryopreservation for transplantation, and transform AFP genes into plants to improve plant cold resistance and thus expand their living environment, and raise their productivity.Whether the plant can exist and grow well is partly determined by the environment, with which plant constantly exchanges materials and energy. Adverse environmental conditions, e. g., low or high temperature, draught, salt and toxic gas, can cause the reversible inhibition of metabolic activity and growth, which will become irreversible, even make plant dead when the...