Hexamerin contributes to nutrient-driven metamorphosis in Anopheles stephensi

The mosquito life cycle involves a rapid transition from aquatic larvae to non-feeding pupae, requiring precise synchronization between nutrient allocation and development. While macronutrients are known to drive metamorphosis, the molecular mechanisms that link amino acids to this transition remain poorly understood. This study investigates the impact of branched-chain amino acid (BCAA) supplementation on the growth and metamorphosis of Anopheles stephensi . We found that BCAA supplementation to standard insectary food accelerated larval growth, enabling larvae to reach the pupal stage approximately 1.5 days earlier than unsupplemented controls. This transition was accompanied by a marked upregulation of Hexamerin ( AsHex ), a dedicated amino acid storage protein, during the late larval (L4) stage. Notably, RNAi-mediated silencing of AsHex significantly impaired pupation, a defect that could not be rescued by BCAA supplementation, suggesting that AsHex -associated nutrient storage contributes to the successful progression of metamorphosis. Next, we evaluated a possible association between AsHex and the nutrient-sensing TOR pathway. Rapamycin treatment delayed the larval-to-pupal transition, similar to AsHex knockdown, suggesting a possible association between AsHex and TOR-dependent developmental regulation. Collectively, our results indicate that AsHex plays a role in coordinating nutritional status with developmental progression during the larval-to-pupal transition. This discovery provides new insights into mosquito growth regulation and identifies AsHex as a potential physiological target for innovative vector control strategies.