Abstract:  The pea aphid, Acyrthosiphon pisum, is an important piercingsucking pest. The secreted saliva plays roles in feeding host plants and virus transmission. In order to explore the function of saliva proteins, we cloned an unknown protein family that is highly expressed in salivary glands of the pea aphid. The family consists of 13 genes, which encode 14 proteins, and four of them are highly expressed in salivary glands. The family is unique to aphids and enriched in cysteine. Fourteen cysteines are conserved, 6 of which form three CXXC domains. Genes of this family have no introns and are distributed in 9 scaffolds of the aphid genome. Semi-quantitative reverse transcription PCR showed that there was no stage-specific expression for this family. We speculate that the expression of this family may be tissue-specific and this protein family probably has the functions of oxidoreductases or DNA methyltransferases.

Key words: Acyrthosiphon pisum, protein family, saliva proteins, developmental stage, gene cloning, gene expression