A protein from the salivary glands of the pea aphid, Acyrthosiphon pisum, is essential in feeding on a host plant. Proc Natl Acad Sci U S A

Department of Entomology, Kansas State University, Manhattan, KS 66506, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 08/2008; 105(29):9965-9. DOI: 10.1073/pnas.0708958105
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In feeding, aphids inject saliva into plant tissues, gaining access to phloem sap and eliciting (and sometimes overcoming) plant responses. We are examining the involvement, in this aphid-plant interaction, of individual aphid proteins and enzymes, as identified in a salivary gland cDNA library. Here, we focus on a salivary protein we have arbitrarily designated Protein C002. We have shown, by using RNAi-based transcript knockdown, that this protein is important in the survival of the pea aphid (Acyrthosiphon pisum) on fava bean, a host plant. Here, we further characterize the protein, its transcript, and its gene, and we study the feeding process of knockdown aphids. The encoded protein fails to match any protein outside of the family Aphididae. By using in situ hybridization and immunohistochemistry, the transcript and the protein were localized to a subset of secretory cells in principal salivary glands. Protein C002, whose sequence contains an N-terminal secretion signal, is injected into the host plant during aphid feeding. By using the electrical penetration graph method on c002-knockdown aphids, we find that the knockdown affects several aspects of foraging and feeding, with the result that the c002-knockdown aphids spend very little time in contact with phloem sap in sieve elements. Thus, we infer that Protein C002 is crucial in the feeding of the pea aphid on fava bean.

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    • "Moreover, there are proteins in the saliva of M. persicae and pea aphids, Acyrthosiphon pisum, Harris that affect the metabolism of the host plant and might be involved in the host plant acceptance by aphids (Will et al. 2007; Pitino et al. 2011; Pitino and Hogenhout 2013; Nicholson et al. 2012). Mutti et al. (2008) demonstrated that a salivary protein is crucial in the feeding of Acyrthosiphon . pisum, on fava bean (Vicia faba), and De Vos and Jander (2009) found that M. persicae produces a salivary proteinaceous elicitor that induces defence responses in Arabidopsis thaliana. "
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    • "Aphid effectors are able to promote aphid virulence upon transient and/or transgenic over expression. For example, the effector C002, which was first identified in A. pisum, is an abundant salivary protein that is essential for aphid feeding (Mutti et al. 2008). "
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    • " - down in various insects have been previously documented . Injection of dsRNA directly into the insect hemocoel is the most common method of delivery . For example , injection of C002 dsRNA into the pea aphid , Acyrthosiphon pisum , resulted in down - regulation of the endogenous transcript and in reduced survival of aphids on fava bean plants ( Mutti et al . , 2006 , 2008 ) . Beet armyworm , Spodoptera exigua , injected with chitin synthase dsRNA displayed larval abnormalities such as disorder in the insect cuticle and no expansion of the trachea epithelial wall ( Chen et al . , 2008 ) . Likewise , injection of the red flour beetle , Tribolium casta - neum , with chitin synthase dsRNA resulted in disrupt"
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