Differential gene expression profiles in the salivary gland of Orius laevigatus

•Sialotranscriptome of a predatory flower bug was analyzed.•Twenty nine salivary gland-specific transcripts were found in the library.•Digestive enzymes, specifically hemolysin, were the major components of the saliva.•Several major contigs encoded secretory proteins with unknown function.

To determine differential gene expression profiles in the salivary gland of a predatory flower bug species, Orius laevigatus (Hemiptera: Anthocoridae), a subtractive cDNA library was constructed by suppression subtractive hybridization. The major transcripts encoding trypsins [30.4% of the total expressed sequence tags (ESTs)] were eliminated from the library in silico, and the remaining salivary gland-specific genes were investigated. A total of 501 ESTs were clustered and assembled into 126 contigs (63 multiple sequences and 63 singletons). Approximately 58% of them were matched to insect genes. In total, 29 contigs (163 ESTs) in the library were determined to be differentially transcribed in the salivary gland. A hemolysin-like protein populated 8.2% (42 ESTs) of the library. Hemolysin is known to destruct cells, including blood cells, by forming pores on the cell membrane, likely facilitating O. laevigatus feeding. Digestive enzymes and antimicrobial proteins were also identified from the salivary gland-specific library. Genes related to homeostasis, antioxidation, anticoagulation and neuropeptide or peptide hormone processing were also found to be transcribed in the O. laevigatus salivary gland. Several major contigs encoded putative secretory salivary proteins, but their functional assignments were not identified in existing protein databases. The discovery of salivary gland-specific genes supports further studies on biologically active components in the saliva of O. laevigatus.

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