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Division of labour is an important organising principle of complex biological systems that has evolved independently several times and is based on dynamic gene regulation. Eusocial insects exhibit flexible allocation of workers to different tasks. We will investigate the molecular determinants that allow workers to behaviourally specialize but also switch tasks, and uncover the task-specific epigenetic and transcriptomic landscape of T. longispinosus. We will socially manipulate colony demography and elucidate the transcriptional regulation of task switching using a multi-omics approach.

Division of labour in social insects is a well-known example of polyphenism, in which individuals exhibit very different behavioural phenotypes despite being highly genetically related. This behavioural plasticity, evident in brood care or foraging specialists, is associated with differences in gene expression. Therefore, social insects are excellent models for studying the relationship between phenotypic plasticity and the regulation of gene expression. Although plasticity of various social behavioural traits has been demonstrated, the molecular mechanisms underlying these complex social behaviours are still largely unclear. Epigenetic regulation of behavioural plasticity should allow workers to dynamically adapt their behaviour to colony demands and environmental changes, which is critical for colony fitness. 

During my PhD, we will characterize the task-specific epigenetic and transcriptomic landscape of workers of the ant Temnothorax longispinosus. To characterize the transcriptomic and epigenetic changes associated with task reversal, we will use experiments with social manipulation of colony demography. To this end, we will remove nurses and undefined workers to induce a switch to brood care behaviour in at least some of the foragers. We know that task performance and underlying gene expression is largely independent of age or fecundity and is more related to the behaviour itself (Kohlmeier et al. 2019). Thresholds for responding to task-related stimuli vary due to internal (e.g., hormonal) and external (e.g., interactions with workers) factors. Consistent with this individual variation, we expect that some foragers will switch from foraging to brood care (reverted nurses), while others will remain foragers. We will conduct a task-reversal experiment with multiple transition points and examine shifts in gene and epigenetic activity across various time points in nurses, reverted nurses, and stable foragers. In this way, we can determine how long and which steps it takes for a forager to shift its transcriptional regulation and investigate whether there are traces of an epigenetic memory. Using an integrative multi-omics approach, we aim to uncover the regulatory processes that control division of labour. Finally, we propose to functionally validate our results by knockdown experiments. Overall, we aim to contribute to our understanding of the evolution and molecular regulation of division of labour in social insects and beyond.