Digestive gene expression profiles in the salivary glands and gut of tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae)

Authors: Perera, Omaththage; Shelby, Kent; Pierce, Calvin; Snodgrass, Gordon

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2021
Publication Date: 5/11/2021
Citation: Perera, O.P., Shelby, K., Pierce Iii, C.A., Snodgrass, G.L. 2021. Digestive gene expression profiles in the salivary glands and gut of tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae). Journal of Insect Science. 21:3. https://doi.org/10.1093/jisesa/ieab028.
DOI: https://doi.org/10.1093/jisesa/ieab028

Interpretive Summary: The tarnished plant bug, Lygus lineolaris, feeds on host plants by secreting saliva containing digestive enzymes after probing the tissue. A few salivary gland digestive enzymes have been characterized previously, but complete repertoire of digestive enzymes have not been studied in this insect. In this study, we characterized 126 carbohydrate, protein, and lipid processing enzymes, including 87 novel sequences, by cloning and sequencing. Quantitative evaluation of these digestive genes in the gut and salivary gland of adult tarnished plant bugs indicated that most proteases and all polygalacturonase genes and two xylanase-like genes were exclusively expressed in salivary glands. Six of the proteases were not detected in either gut or salivary gland. Most of the carbohydrate and lipid processing enzymes were differentially expressed in the gut.

Technical Abstract: Host plant preference of agricultural pests may shift throughout the growing season allowing the pests to persist on wild hosts when crops are not available. Lygus Hahn bugs are severe pests of cotton during flowering and fruiting stages but can persist on alternative crops or on weed species. Diversity of digestive enzymes produced by salivary glands and gut tissues play a pivotal role in an organism’s ability to utilize various food sources.Polyphagous insects produce an array of enzymes that can process carbohydrates, lipids, and proteins. In this study, digestive enzyme repertoire of the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), was identified by high-throughput sequencing followed by cDNA cloning and sequencing. This study identified 87 digestive genes including 30 polygalacturonases (PG), one beta galactosidase, three alpha glucosidases, six beta glucosidasesone, 28 trypsin-like proteases, three serine proteases, one apyrase-like protease, one cysteine protease, 12 lipases, and two transcripts with low similarity to a xylanase A-like genes. RNA-Seq expression profiles of these digestive genes in adult tarnished plant bugs revealed that 57 and 12 genes were differentially expressed in the salivary gland and gut (>=5-fold, P<=0.01), respectively. All polygalacturonase genes, most proteases, and two xylanase-like genes were differentially expressed in salivary glands, while most of the carbohydrate and lipid processing enzymes were differentially expressed in the gut. Seven of the proteases (KF208689, KF208697, KF208698, KF208699, KF208700, KF208701, and KF208702) were not detected in either the gut or salivary glands.