Abstract
The present review discusses the molecular mechanisms of injury caused by low temperatures and/or freezing. The review is intended mainly for insect environmental physiologists who focus on the effects of low temperatures. The review successively discusses (1) the effects of low temperatures on the structure and function of macromolecules; (2) the effects of freezing on cells and macromolecules and (3) the mechanisms of damage during thawing and post-thaw. The review shows that injury primarily occurs at the molecular level in terms of damage to proteins, nucleic acids and biological membranes. The damage to macromolecular structures occurs as a result of the interaction between the effects of temperature, ice formation and resulting secondary effects such as osmotic stress, increased concentration of solutes, cellular freeze dehydration, disruption of ionic balance and oxidative stress. The present review attempts to identify gaps in our knowledge on the mechanisms of cold injury in organisms and proposes possible future directions that could contribute to filling the gaps.
Highlights
Temperature affects every aspect of the life of insects and other organisms, from the rate of biochemical reactions, to activity, growth, development and reproduction
The present review shows that contrary to the common perception, the mechanisms of cold injury in organisms are largely known, if we change our perspective and focus on the molecular level
The formation of ice causes injury either directly by mechanical forces exerted by growing ice crystals or indirectly through various physico-chemical effects
Summary
Temperature affects every aspect of the life of insects and other organisms, from the rate of biochemical reactions, to activity, growth, development and reproduction. The present review will focus mostly on the damaging effects of subzero temperatures and of freezing (“cryothermia”), mainly at the molecular level. The effects of “low” temperatures above CTmin mostly result from “impaired processes”, causing no physical damage to the organism and they may include for example decreased metabolism, growth, reproduction, development rate, or chill coma. The research on cold injury in insects and other organisms is often only indirect, limited to a search for the conditions such as temperature or duration of exposure at temperatures under which mortality (an ultimate result of cold injury) starts to occur (e.g. Boychuk et al, 2015; Stephens et al, 2015; Rozsypal et al, 2018a). The present review shows that contrary to the common perception, the mechanisms of cold injury in organisms are largely known, if we change our perspective and focus on the molecular level. The last section of the review will focus on the mechanisms of damage during thawing and post-thaw
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