Insulin receptor substrate influences female caste development in honeybees.

The insulin/insulin-like signalling (IIS) network is conserved among animals and is central to growth and development. In eusocial honeybees (Apis mellifera), IIS is hypothesized to shape female caste fate. We tested this hypothesis via RNA interference (RNAi) knockdown of the insulin receptor substrate (IRS) homologue, a key adaptor protein in IIS. Female larvae naturally develop into queens (reproductives) or workers (helpers) after being fed rich versus limited diets, respectively. Feeding larvae a rich diet mixed with dsRNA (double stranded RNA) targeting irs gene transcript decreased irs mRNA abundance and caused development of worker morphology. Controls receiving rich larval diet and control dsRNA developed queen morphology. Whole-body mass spectrometry profiling of larvae collected 72, 96 and 120 h after dsRNA treatments revealed proteomic differences between irs gene knockdowns and controls, including levels of hexamerin 110, a storage protein connected to natural caste differences.