microRNAs as Cryoprotectants
Freeze tolerance in insects is associated with a variety of adaptations including production of cryoprotectants, specialized proteins that regulate ice formation, and energy-saving mechanisms that strongly suppress the rates of metabolic processes in the oxygen-limited frozen state.
A group of Canadian researchers hypothesized that microRNAs (miRNAs), small non-coding transcripts that bind to mRNA, could play a role in the global regulation of energy-expensive mRNA translation in frozen insects and would be modulated at subzero temperatures.
Expression levels of miRNA species were evaluated in control (5°C) and frozen (-15°C) goldenrod gall fly larvae, Eurosta solidaginis, using LC Sciences’ miRNA microarray service. Levels of several miRNAs were significantly reduced in frozen larvae whereas others rose significantly in frozen larvae. Target prediction for two of the differentially regulated miRNAs, miR-277-3p and miR-284, revealed potential regulation of transcripts involved in translation and the Krebs cycle.
These data constitute the first report that differential expression of miRNAs occurs in a freeze tolerant insect and suggest a mechanism for reversible gene regulation during prolonged periods of freezing over the winter months, a mechanism that can be rapidly reversed to allow renewed translation of mRNA when temperatures rise and insects thaw.
- Courteau LA, Storey KB, Morin PJ. (2012) Differential expression of microRNA species in a freeze tolerant insect, Eurosta solidaginis. Cryobiology [Epub ahead of print]. [abstract]
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