Life on hold: a physiological model of a low-temperature clock in a diapausing insect

• Applicant: Professor Dr. Philipp Lehmann
• Subject Area: Animal Physiology and Biochemistry
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 536846905

In seasonal environments, part or the year is generally too harsh or resource-poor for development and reproduction in small ectothermic animals, and is commonly spent in some form of resting stage. One such resting stage is diapause, a deep state of metabolic suppression and developmental arrest. Diapausing insects enjoy a range of benefits, including abiotic stress resistance and energy expenditure and an apparent pause in aging related processes. Diapause is however not a state of complete biological inactivity, but a highly programmed series of sequential physiological states. First diapause is induced, then maintained, and finally is terminated. Throughout these transitions low temperatures are crucial in order for diapause to progress. Low temperatures help insects save energy and maintain appropriate fluxes through metabolic pathways. Importantly, without accumulation of sufficient cold, returning warm conditions in spring are not able to stimulate development. The physiological mechanisms behind this low-temperature counter are however poorly understood, which constitutes a serious knowledge gap, since climate change is associated with warming winters. In this project, I aim to clarify how low temperatures affect diapause physiology in the butterfly species Pieris napi, a typical temperate insect that undergoes pupal diapause during winters. My research group has investigated diapause biology in this species for over a decade and has developed a large methods toolbox that we can access. I aim to address two interconnected questions primarily centered around protein biology, which is a relatively understudied functional level. Utilizing a diverse array of methods, ranging from large-scale "omics" techniques to functional assays of protein activity states and targeted manipulations of peptide hormone receptors and pathways, I seek to understand (i) how diapausing insects maintain the correct balance between metabolic inactivity (i.e., metabolic suppression) and activity, and (ii) the mechanisms behind cold-counting during diapause. The central assumption behind these questions is that synthesizing proteins de novo at low temperatures is not ideal, and instead, that the transitions are predominantly governed by changes in activity states of proteins synthesized before winter, such as phosphorylation and acetylation of transcription factors, or by relocating proteins from storage sites to areas of activity, such as the cell membrane. In conclusion, this project aims to provide a comprehensive investigation into how P. napi effectively manages complex metabolic transitions at low temperatures and utilizes low temperatures as a time-keeping mechanism during winter. By shedding light on the intricate mechanisms underlying diapause in this butterfly species, I hope to contribute significantly to our understanding of how insects adapt to changing environmental conditions, particularly in the context of ongoing climate change.

• DFG Programme: Research Grants
• Co-Investigators: Professorin Dr. Dörte Becher; Professor Dr. Michael Lalk