Effects of RNAi-based silencing of chitin synthase gene on moulting and fecundity in pea aphids (Acyrthosiphon pisum)

Abstract

The pea aphid, Acyrthosiphon pisum , is an important agricultural pest and an ideal model organism for various studies. Chitin synthase (CHS) catalyses chitin synthesis, a critical structural component of insect exoskeletons. Here, we identified a CHS gene from A . pisum , ApisCHS . The ApisCHS expression profiles showed that ApisCHS was expressed in various developmental stages and in all tested tissues of A . pisum , including the epidermis, embryo, gut and haemolymph. Notably, ApisCHS exhibited peak expression in the middle of each nymphal period and was extremely highly expressed in the epidermis and embryo. RNA interference (RNAi) showed that ~600 ng of dsRNA is an effective dose for gene silencing by injection for dsRNA delivery; moreover, 1200 ng·μL −1 dsRNA induced CHS gene silencing by a plant-mediated feeding approach. A 44.7% mortality rate and a 51.3% moulting rate were observed 72 h after injection of ds ApisCHS into fourth-instar nymphs, compared with the levels in the control (injected with ds GFP ). Moreover, a longer period was required for nymph development and a 44.2% deformity rate among newborn nymphs was obtained upon ingestion of ds ApisCHS . These results suggest that ApisCHS plays a critical role in nymphal growth and embryonic development in pea aphids, and is a potential target for RNAi-based aphid pest control.

Expression Dynamics of Core RNAi Machinery Genes in Pea Aphids Upon Exposure to Artificially Synthesized dsRNA and miRNAs

“…We believe the expressions of 25 core genes upon the dsRNA treatment are dose-dependent as well as in sufficient dose presenting a time points-based dynamics. For instance, the response of core machinery was detected in both 24 h [36] and 36 h in the current study. In addition, the RNAi efficiency of the targeted gene was the highest at the 36 h [36].…”

“…This trend occurred in the dsGFP treated sample but not in the dsHB treated sample. We previously observed that the induction of these three genes occurred 24 h after dsRNA injection (600 ng per aphid) [36], implying that the variation of gene expression level induction is associated with the time of sample collection and the physiological stage of the aphids. We believe the expressions of 25 core genes upon the dsRNA treatment are dose-dependent as well as in sufficient dose presenting a time points-based dynamics.…”

“…After injection, aphids were put on broad bean seedlings and 36 h, the aphids were collected for RNA extraction. We choose 36 h to collect samples based on our previous study [36]. The RNAi efficiency of the targeted gene was optimal at this time point.…”

Evaluation of a cuticle protein gene as a potential RNAi target in aphids

“…This method was also used in the brown citrus aphid, Aphis citricidus , for silencing genes encoding insulin receptors, vitellogenin, 3‐ketoacyl‐CoA thiolase, and glycogen phosphorylase . In Acyrthosiphon pisum , silencing of the chitin synthase 1 gene through leaf‐based dsRNA delivery disrupted nymph molting and embryo development …”

“…2,12,13 In Acyrthosiphon pisum, silencing of the chitin synthase 1 gene through leaf-based dsRNA delivery disrupted nymph molting and embryo development. 14 Insect cuticle is the primary protective barrier against environmental stresses. 15,16 The main structural components of the cuticle are chitin, lipids, catecholamines, minerals, and cuticle proteins (CPs).…”