Grant: Discovery Grants Program - Individual

Insect species represent more than 70% of all animal species and have colonized just about every habitat on earth. As a result, they are confronted to a large range of temperature changes, and the scope of their thermal tolerance is thus crucial for their geographic distribution, even more so in the context of climate change. We recently showed that the type of fuel used by mitochondria (the powerhouse of the cell) to produce ATP (the cellular energy currency) is drastically changed at high temperatures in a comparative model of fruit flies (drosophila), and that this change is highly correlated with heat thermal tolerance. The causes and consequences of this switch is however still unknown. Moreover, insects have developed different strategies to cope with variation in environmental temperatures. For example, some flying insects perform pre-flight thermogenesis which enables them to maintain a high thorax temperature in order to fly at relatively low ambient temperature. Eusocial insects such as the domesticated honeybee, Apis mellifera, also display behavioral strategies to keep the queen inside the hive at around 35°C during winter through shivering thermogenesis, even when ambient temperatures are below 10°C (temperature at which individual honeybees are falling into a coma). Recently, we demonstrated that in mitochondria of winter shivering honeybees, the same switch of fuel observed at high temperature in Drosophila is occurring, suggesting that the type of substrate used by mitochondria might also be important for maintaining an adequate temperature inside the hive during winter. However, the underlying mechanisms of this change and its significance on the physiology of honeybees have yet to be determined. The general objective of this research program is thus to understand the implication of mitochondrial fuel changes in the different mechanisms underlying metabolic flexibility, thermal tolerance, thermogenesis and adaptation to temperature in insects. For this purpose, I will use state of the art techniques to measure mitochondrial oxygen consumption at several steps of the electron transport system with different fuel types, site specific reactive oxygen species generation (a metabolic by-product of mitochondrial respiration), ATP production, activities and transcript abundance of key metabolic enzymes, as well as metabolomics and proteomics analyses. Combined with powerful genetic tools such as the UAS/Gal4 system in Drosophila allowing to perform specific targeted knock-down as well as chemical tools such as reserpine which inhibits thermogenesis in honeybees, this research program will shed light on the fundamental mechanisms underlying thermal tolerance and adaptation to temperature in insects. This knowledge is absolutely needed considering the socio-economic importance of insects that serve important ecosystem services such as pollination and the recent exacerbated impacts of climate change.