Cuticular proteins and seasonal photoperiodism in aphids.

For poikilotherm animals such as insects, extreme temperatures can be a severe issue in continental regions. Aphids, which reproduce in spring and summer by viviparity, are prone to death in hard winter conditions. These species exhibit reproductive plasticity adapted to winter by producing oviparous females in autumn, which lay overwintering eggs. This switch is driven by photoperiodism, and long nights are sufficient to trigger the change in reproductive mode. Global transcriptomic analyses applied to the pea aphid Acyrthosiphon pisum for which genomic resources are now available have allowed the identification of several genetic programs regulated by photoperiod shortening. Unexpectedly, one of these genetic programs concerns cuticle proteins and cuticle structure. This opens new tracks for investigations and poses new hypotheses on the link between cuticle modification and neuronal signalisation of photoperiod in aphids in response to seasonal photoperiodism. This review focuses on the description of cuticular protein genes in the pea aphid and their regulation during the change of reproductive mode.