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Insect cold survival has drawn increased attention in recent years, prompting a new classification of survival phenotypes that reflect the ecological and physiological differences in the manner in which insects survive the winter. In addition, more is known about the nature of cold injury and its effects on an insect system from the whole body to the subcellular level, although much remains to be discovered. Other than the detection of misfolded protein by the heat shock response, signal transduction of low temperatures by insects is largely unexplored. Recent advances in Drosophila and a few vertebrate systems reveal the potential importance of transient receptor potential ion channels in low temperature signal transduction, and membrane fluidity also possibly plays a role in the detection of low temperatures by insects. Physiological changes that occur in insect cells as a result of low temperatures or in anticipation of low temperatures include the induction of a suite of heat shock proteins, metabolic polyol synthesis, antifreeze protein production, and the induction of extracellular ice nucleation. In addition, a variety of new genes are now known to be induced upon cold exposure, but the roles of these molecules in cold survival are still largely unknown. |
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