CHARACTERIZATION AND LOCALIZATION OF THE ICE-NUCLEATING ACTIVE AGENTSIN LARVAE OF THE RICE STEM BORER, CHILO-SUPPRESSALIS WALKER (LEPIDOPTERA, PYRALIDAE)

Chemical properties of the ice-nucleating active agents (INAs) distrib uted in the muscle of diapausing larvae of the rice stem borer, Chile suppressalis Walker were studied. Sensitivity to protease indicated th at the INAs were proteinaceous. The INAs were stable at at least 50 de grees C for 5 min, and active over a broad pH range (pH 2.0 to 8.0) an d after delipidation treatments. These results suggest that the chemic al characteristics of the INAs of the muscle in the diapausing larvae are similar to those of the exogenous agents in the nondiapausing ones in Fusarium sp. After differential centrifugation of muscle homogenat e of the diapausing larvae, the crystallization temperature of the 105 ,000g pellet was the highest of all fractions separated, implying that INAs are present in microsome membrane. (C) 1995 Academic Press, Inc.