Aphid wing plasticity: hormonal and epigenetic control mechanisms.

Insect polyphenisms are an extreme form of phenotypic plasticity that arises when environmental cues are transduced into endocrine signals that redirect development, producing discrete morphs from a single genome. Aphid wing polyphenisms have been important to establishing this framework. In asexual females, stress-inducing conditions result in winged daughters, whereas benign environments yield wingless offspring. Classic work emphasized juvenile hormone, but recent evidence points to a causal role for ecdysone. Upstream neurotransmitter pathways, including glutamate and possibly dopamine, translate tactile crowding into endocrine responses, while downstream processes such as autophagy, Transforming growth factor (TGF-β) signaling, and insulin signaling shape wing development. Epigenetic mechanisms, including microRNAs and chromatin modifiers, stabilize morph-specific transcriptional states. Collectively, these studies outline a multi-step process, from environmental sensing to neuroendocrine integration, hormonal signaling, and epigenetic maintenance, that governs aphid wing plasticity. Emerging genomic and chromatin profiling tools now position aphids as a powerful model for dissecting environmentally induced developmental plasticity.