A single gene associated with insulin signaling likely drove the evolutionary rise of an ant queen's reproductive royalty, researchers suggest. Their findings hint that development of one of the more complex animal societies on Earth is strongly influenced, if not determined by, expression of a single gene. All ants are thought to be eusocial insects, with most individual ants within a colony foregoing their own reproductive potential to support an egg-laying queen. According to the new study, this behavior is regulated through insulin signaling and expression of the gene insulin-like peptide 2 (ilp2). The strict reproductive roles common to eusocial ants are thought to mirror an ancestral subsocial lifecycle when common ancestors of ants alternated between reproductive and brood care phases. Eventually, this cyclic reproductive behavior adapted to reflect the fixed roles of egg-bearing queens and brood-caring workers of eusocial colonies seen today. However, the origin of eusociality and its genetic underpinnings remain unclear, leaving open questions about what allows queens to lay eggs but prevents workers from doing so, among others. Here, using a transcriptomic approach, Vikram Chandra and colleges searched for differentially expressed genes in the brains of reproductive and non-reproductive ants from several ant species, members of which exhibited a range of reproductive strategies. In reproductive ants, the gene insulin-like peptide 2 (ilp2) was consistently highly expressed, the authors report. The authors investigated the role of ilp2 on the reproductive cycles of clonal raider ants, which exhibit a less clear division of labor. In these ants, they found that the presence of larvae reduced expression of ilp2. Boosting the levels of the peptide associated with ilp2, however, could override these larval signals and establish a more strict split between worker and queen. Combined, Chandra et al.'s findings implicate insulin signaling in the regulation of any eusociality and provide a model for the origins of their behavior through increased nutritional differences amplified by larval signaling in subsocial ancestors.
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Journal
Science