Vitellogenin and its receptor play essential roles in the development and reproduction of the brown citrus aphid, Aphis (Toxoptera) citricidus

Abstract

Vitellogenin (Vg) and its receptor (VgR) play a key role in the reproductive process and development of insects. Aphids are a group of high-fecundity insect species with pseudoplacental viviparity, but the roles of their Vg and VgR genes have not been investigated yet. The brown citrus aphid, Aphis (Toxoptera) citricidus, is a major insect pest of citrus and the main vector of Citrus tristeza closterovirus. In this study, we identified and characterized these two genes, designated as AcVg and AcVgR, from the brown citrus aphid. We found that AcVg has lost the DUF1943 domain that is present in other insect Vgs. Silencing of AcVg and AcVgR led to a delay in the nymph-adult transition, a prolonged prereproductive period, and a shortened reproductive period, which in turn resulted in slower embryonic development and fewer new-born nymphs. Interestingly, silencing of AcVg decreased the transcript level of AcVgR, but silencing of AcVgR resulted in increased transcript levels of AcVg. In addition, silencing of Vg/VgR had similar phenotypes between alate and apterous morphs, suggesting that the functions of these two genes are the same in the two wing morphs of the aphid. Our results demonstrate that Vg and VgR are involved in various aspects of aphid development and reproduction. Further studies on the synthesis of Vg could help to elucidate the reproductive mechanism and provide information that will be useful for developing new pest control strategies.

Topical dsRNA delivery induces gene silencing and mortality in the pea aphid

“…pisum , Acβact and AcEF1α for Ap. citricidus , and Mpactin and Mppara for M. persicae (Table ), were included to normalize the qPCR data, and the relative expression levels of the tested genes were calculated following the framework of qBase +…”

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

“…The RNAi bioassay was performed by feeding dsRNA through a citrus leaf (for A. citricidus ), bean leaf (for Ac. pisum ), or Brassica leaf (for M. persicae ) as described previously . Briefly, a stem with a fresh leaf was inserted into a 1.5 Ml centrifuge tube containing 1.0 mL of dsRNA (1500 ng μL –1 ).…”

“…pisum), or Brassica leaf (for M. persicae) as described previously. 13 Briefly, a stem with a fresh leaf was inserted into a 1.5 Ml centrifuge tube containing 1.0 mL of dsRNA (1500 ng μL -1 ). The tube was then transferred to a plastic tube.…”

“…Alternatively, dsRNA uptake through a plant leaf has been effective in the silencing of the ecdysone receptor gene in the whitefly, Bemisia tabaci , and causing nymph mortality . 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 …”

“…11 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. 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.…”