Dopamine pathway characterization during the reproductive mode switch in the pea aphid

Abstract

AbstractAphids are major pests of most of the crops worldwide. Such a success is largely explained by the remarkable plasticity of their reproductive mode. They reproduce efficiently by viviparous parthenogenesis during spring and summer generating important damage on crops. At the end of the summer, viviparous parthenogenetic females perceive the photoperiod shortening and transduce this signal to their embryos that change their reproductive fate to produce sexual individuals: males and oviparous females. After mating, those sexual oviparous females lay cold-resistant eggs. Previous studies based on large-scale transcriptomic analyses suggested dopamine pathway might be a key player in the integration of the autumnal photoperiod shortening signal to promote the reproductive mode switch. In this study, we investigated the role of dopamine pathway in the photoperiodic response of the pea aphid Acyrthosiphon pisum. We first analysed the level of expression of ten genes of this pathway in embryos and larval heads of aphids reared under long days (asexual producers) or short days (sexual producers) conditions. We then performed in situ hybridization experiments to localize in embryos the ddc and pale transcripts that are coding for two key enzymes in dopamine synthesis. Finally, Using CRISPR-Cas9 mutagenesis in eggs produced after the mating of sexual individuals, we targeted the ddc gene. We could observe strong melanization defaults in ddc mutated eggs, which confidently mimicked the Drosophila ddc phenotype. Nevertheless, such a lethal phenotype did not allow us to investigate the precise role of ddc in photoperiod shortening signal integration leading to the reproductive mode switch.