Apolipoprotein D3 is required for long‐chain cuticular hydrocarbon accumulation and water retention in Acyrthosiphon pisum

Abstract BACKGROUND The pea aphid, Acyrthosiphon pisum , is a damaging phloem‐feeding pest of legume crops, and RNA interference (RNAi)‐based targeting of stress‐adaptation genes offers a promising route for target‐specific pest management. Apolipoprotein D (ApoD) proteins are putative lipid carriers in insects, but the function of the chromosome‐3 paralog ApApoD3 in aphid cuticular waterproofing remains unknown. We investigated whether ApApoD3 regulates cuticular hydrocarbon (CHC) accumulation and desiccation tolerance in A. pisum using RNAi, GC–MS‐based CHC profiling, water‐balance and survival assays, fecundity assessment, and RNA sequencing. RESULTS Injection of ds ApApoD3 significantly suppressed ApApoD3 expression, producing 47.47% knockdown at 48 h and maintaining significant silencing through 96 h. ApApoD3 depletion reduced total CHC abundance by 28.69% and significantly reduced long‐chain n ‐alkanes, specifically n ‐C 25 – n ‐C 30 and n ‐C 32 . This disruption of the cuticular lipid barrier was accompanied by a 19.44% reduction in body water content and an approximately 2.05‐fold increase in water loss rate. Under severe desiccation, no ApApoD3 ‐silenced aphids survived at 36 h, whereas 26.67% of controls remained alive. Separately, cumulative fecundity was significantly reduced at all observation times from 12 to 120 h after ApApoD3 silencing. Transcriptome analysis identified 187 differentially expressed genes and revealed enrichment of neuropeptide signaling, hormone activity, and G protein‐coupled receptor binding, indicating a broad transcriptional response to ApApoD3 silencing. CONCLUSION ApApoD3 is required for long‐chain CHC homeostasis, water retention, desiccation tolerance, and reproductive fitness in A. pisum . These findings identify ApApoD3 as a mechanistically supported RNAi candidate for stress‐sensitization‐based aphid management. © 2026 Society of Chemical Industry.