Parental silencing of a horizontally transferred carotenoid desaturase gene causes a reduction of red pigment and fitness in the pea aphid

Abstract BACKGROUND Aphids obtained carotenoid biosynthesis genes via horizontal gene transfers from fungi. However, the roles of these genes in the contributions of in aphids’adaptation and whether these genes could be used as RNAi‐based pest control targets are not yet clear. Thus, in this study we used parental RNAi to analyze the potential function of a carotenoid desaturase gene ( CdeB ) by combined molecular and chemical approaches in the pea aphid ( Acyrthosiphon pisum ). RESULTS Transcriptional analyses showed that CdeB was significantly more highly expressed in the red morphs compared to the green ones and was associated with the production of red carotenoid. Co‐transferring of pET28a‐ CdeB (the CdeB gene was cloned into pET28a) and pACCRT‐EIB (produced lycopene) showed a deep red color in the bacterial precipitate and produced more of a red pigment, lycopene, in vitro . Parental gene‐silencing of CdeB resulted in a lower body color intensity in the treated aphids and following generations in vivo . Interestingly, the ds CdeB treatment also reduced aphid performance as reflected by a delay in nymphal developmental duration, lower weight, smaller number, and altered age structure of the population. CONCLUSION Our results demonstrate that CdeB is involved in red color formation and the silencing of this gene by parental RNAi reduced fitness in the pea aphid. The results enhance our understanding of the biosynthesis of carotenoid in aphids and provide insights into the potential ecological significance of carotenoids in the adaptation of the aphid's biology to the environment and developing environmentally friendly control strategies for this pest.