Altered insulin signaling in ant queens may endow them with their characteristic longevity, despite being the only reproductives in a colony, researchers report. In most living organisms, there is a trade-off between reproduction and lifespan. This is largely because animals that have many offspring often devote significant nutritional and metabolic resources to reproduction at the expense of their own longevity. The insulin and insulin-like growth factor signaling pathway is thought to underlie the anti-correlation between reproduction and shortened lifespan. Ants are an exception to this pattern, however. In any colony, reproductive activity is limited to one or a few queens. Reproductive queens can live decades, many lifetimes beyond the non-reproductive workers of a colony, and lay millions of eggs. In some ant species, such as Harpegnathos saltator, workers can change castes and become reproductive pseudoqueens, or gamergates, when a queen dies or is removed. Despite being born as workers, gamergates can live up to five times longer than their previous counterparts. Additionally, gamergates can revert to workers (reverters) when placed in a colony with an established worker caste, returning to a shortened lifespan. It is not clear how this longevity associated with reproduction is regulated in these animals, especially during active reproduction. To assess the relationship between reproduction and longevity, Hua Yan and colleagues performed bulk RNA sequencing on tissues important for reproduction and metabolism of worker ants, gamergate, and reverted H. saltator and compared the ‘gene expression during caste change. As expected, Yan et al. found that insulin was regulated to promote oogenesis in gamergates, however, this did not lead to a shorter life span as it does in other animals. The authors propose that part of the insulin signaling pathway (the branch that activates the protein kinase AKT) is inhibited in the fat body of gamergates and that this may be mediated by an Imp-L2 protein. According to the authors, decreased AKT activity may allow H. saltator queens and pseudoqueens to live longer.
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