|COLINET, HERVE - University Of Rennes|
|Rinehart, Joseph - Joe|
|GREENLEE, KENDRA - North Dakota State University|
Submitted to: Journal of Experimental Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2018
Publication Date: 7/23/2018
Citation: Colinet, H., Rinehart, J.P., Yocum, G.D., Greenlee, K.J. 2018. Mechanisms underpinning the beneficial effects of fluctuating thermal regimes in insect cold tolerance. Journal of Experimental Biology. 221: jeb164806. https://doi.org/10.1242/jeb.164806.
Interpretive Summary: Many industries associated with the mass rearing of insects, including biocontrol programs, sterile insect technique programs, pollination services, and the maintenance of research collections, use cold storage techniques to increase the “shelf-life” of their insects. However, low temperature exposure can lead not only to insect mortality but can reduce the quality of the insect as well. A growing number of studies have demonstrated that using a fluctuation thermal regime (FTR), by which cold storage is interrupted by a daily pulse of high temperature, greatly increases stored insect shelf-life and quality. This commentary assesses the current uses of FTR and reviews the current understanding of the underlying physiological mechanisms involved. Although the authors highlight significant areas where increased understanding are needed, we are of the opinion that the current data supports the use of FTR as an important tool in multiple insect rearing industries.
Technical Abstract: Insects exposed to low temperature often have high mortality or exhibit sublethal effects. A growing number of recent studies have shown beneficial effects of exposing insects to recurrent brief warm pulses during low temperature stress (fluctuating thermal regimes, FTR). The physiological underpinnings of the beneficial effects of FTR on cold survival have been extensively studied over the past few years. Profiling with various ‘–omics’ techniques has provided supporting evidence for markedly different physiological responses between insects exposed to FTR and constant low temperature. Evidence from transcriptomic, metabolomic, and lipidomic studies points to system-wide loss of homeostasis at low temperature and complex repair mechanisms under FTR. Although considerable progress has been achieved in understanding the physiological mechanisms underlying the beneficial effects of FTR, many areas still lack clarity, such as the precise role(s) of heat shock proteins, compatible solutes, or the identification of regulators and key players involved in the observed homeostatic responses. FTR can be particularly beneficial in applied settings, such as for model insects used in research, integrated pest management, and pollination services. Although extremely practical, application of FTR techniques in large-scale facilities may require overcoming some logistical and technical constraints. Finally, FTR seems to be the silver bullet for surviving exposures to low temperature, but before FTR can be widely used, the possible fitness and energy costs must be explored sufficiently.