Insulin signaling in the long-lived reproductive caste of ants

In most organisms, reproduction is correlated with shorter lifespan. However, the reproductive queen in eusocial insects exhibits much longer lifespan than workers. In Harpegnathos ants, when the queen dies, workers can undergo an adult caste switch to reproductive pseudo-queens (gamergates) exhibiting a 5X prolonged lifespan. To explore the relation between reproduction and longevity, we compared gene expression during caste switching. Insulin expression is increased in the gamergate brain that correlates with increased lipid synthesis and production of vitellogenin in the fat body, both transported to the egg. This results from activation of the mitogen-activated protein kinase (MAPK) branch of the insulin signaling pathway. In contrast, the production in the gamergate developing ovary of anti-insulin Imp-L2 leads to decreased signaling of the AKT/FOXO branch in the fat body, consistent with their extended longevity. Samples were collected from three tissues of the Harpegnathos saltator ants. Tissue-specific gene expression profiles were generated from three different ant castes (workers[W], gamergates[G] and revertants[R]). Three different tissues consist of abdominal fat body, ovary, and non-visual brain from each individuals (total of four individuals).