Aminergic regulation of honeybee flight muscles in the context of thermoregulation

• Applicant: Dr. Markus Thamm
• Subject Area: Animal Physiology and Biochemistry ; Sensory and Behavioural Biology
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 418729949

Honey bees (Apis mellifera) have the fascinating ability to actively regulate both their body temperature and the temperature in the bee hive. Heating (thermogenesis) and cooling play a central role in this. For both, the flight muscle in the thorax is of outstanding importance. It is not only used for the purpose of flying. If it gets too warm, they fan with their wings to provide cooling. If it gets too cold, the workers actively produce heat (thermogenesis). This makes honey bees relatively independent of the outside temperature, because it ensures survival in winter and guarantees the best breeding conditions. Thermogenesis can also be used to fight predators. In our past project we could show that octopamine is crucially involved in thermogenesis. Octopamine and its receptors are present in the flight muscle of the honeybee. If this system is disturbed, hypothermia inevitably occurs. Most likely, it is a β-octopamine receptor that promotes thermogenesis. Its activation leads via an intracellular signaling cascade (increase in intracellular cAMP concentration) to an increase in glycolysis output, which is the basis for the energy-hungry work of muscle proteins. Our results also show that cold stress strongly increases transcriptional output. This also includes the genes AmOARβ2 (octopamine receptor gene) or AmGAPDH (important function in glycolysis). In this follow-up project, we want to investigate three larger aspects in more detail. First, thermal stress is the focus here. We want to find out which genes are differentially regulated by cold or heat stress to keep the flight muscle system running. An important part of this will be to work out which genes are up- or down-regulated by octopamine signaling. Second, we want to find out what factors influence thermogenesis performance. Important candidates for this are cold stress and diet. Third, we have been able to detect large amounts of dopamine in flight muscle. Moreover, its concentration varies in interesting ways: In newly hatched bees it is very high, in young bees it is very low and then slowly increases again. Nothing is yet known about the function of dopamine in muscles in general or in the flight muscle of honeybees in particular. We will therefore perform a series of descriptive as well as functional analyses to narrow down the possible function of dopamine.

• DFG Programme: Research Grants
• Co-Investigator: Dr. Markus Ankenbrand