The Role of Akt Signaling in Regulating Developmental Plasticity in Horned Beetles

ABSTRACT Developmental plasticity in response to nutrition is widespread across taxa and has been the subject of numerous studies, yet the molecular mechanisms underlying tissue‐specific plasticity remain poorly understood. The insulin/insulin‐like signaling (IIS) pathway regulates growth in many insects, including the horned beetle Digitonthophagus gazella , a species characterized by male head horn polyphenism. Here, we investigate the role of Akt, a central protein that acts directly upstream of the IIS transcription factor FOXO, a known regulator of horn development. We hypothesized that Akt contributes to nutrition‐responsive trait development, acting in concert with FOXO and other members of the IIS. Using RNA interference (RNAi), we knocked down Akt and assessed its effects on traits that differ in a sex‐ and nutrition‐specific manner. Akt RNAi resulted in a reduction in growth across multiple traits, including overall body size, foretibia, female prothoracic protrusions and male head horns. Transcriptomic analyses of horn tissue across nutrition conditions further showed differential expression of Akt ‐interacting genes, suggesting that complex interactions across IIS pathway components and additional regulatory networks coordinate nutrition‐responsive growth. Together, these results identify Akt as a key regulator of context‑dependent, trait‑ and sex‑specific plasticity in D. gazella , and highlight the complexity of plastic responses and the need for further investigation.