Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2012
Publication Date: 1/9/2013
Citation: Cooper, W.R., Nicholson, S.J., Puterka, G.J. 2013. Salivary proteins of Lygus hesperus (Hemiptera: Miridae). Annals of the Entomological Society of America. 106(1):86-92. DOI: http://dx.doi.org/10.1603/AN12096. Interpretive Summary: Lygus hesperus is a major pest of fruits, vegetables, forages, and cotton in the western United States. Saliva injected into the plant by Lygus bugs digests plant tissues and allows the insects to feed. Researchers at the USDA-ARS laboratories in Shafter, CA and Stillwater, OK analyzed the salivary enzymes discharged into artificial diet by Lygus bugs. They confirmed the presence of previously documented digestive enzymes in Lygus saliva and identified four previously undocumented salivary enzymes that may be involved in the detoxification of plant-defenses. They also identified numerous proteins from two bacterial plant pathogens, Pantoea ananatis and Serratia spp, suggesting that Lygus bugs transmit these disease agents. Results from this study contribute to a better understanding of Lygus salivary constituents and vector potential, which will aid in the development of resistant crops.
Technical Abstract: Lygus hesperus Knight (Hemiptera: Miridae) causes economic damage to a wide-range of crops in the western United States. While stylet-probing, L. hesperus discharge saliva consisting of lytic enzymes that facilitate extraoral digestion of host tissues. L. hesperus saliva primarily consists of polygalacturonases, alpha-amylases, and proteases, but salivary constituents other than these enzymes have not been documented. Improved knowledge of L. hesperus salivary proteins could lead to a better understanding of Lygus – host interactions, and aid in the development of crops that are resistant or tolerant to injury caused by Lygus spp. The objective of our study was to use mass spectrometry to identify salivary proteins of L. hesperus adults. Multiple polygalacturonases and proteases were identified from diet that was stylet-probed and fed upon by L. hesperus. Laccase, alkyl hydroperoxide reductase-like protein, glucose dehydrogenase, and xanthine dehydrogenase were putatively identified in stylet-probed diets using mass spectrometry, and laccase activity was confirmed using a colorimetric assay. This is the first study to identify laccase, alkyl hydroperoxid reductase, glucose dehydrogenase, and xanthine dehydrogenase from L. hesperus saliva; we propose these enzymes target plant-defense compounds. Nearly 100 proteins from the bacterial plant pathogen, Pantoea ananatis and nine proteins from Serratia spp. were identified in stylet-probed diets. These results suggest L. hesperus may vector these plant pathogens. Our study adds to the list of documented L. hesperus salivary proteins, and provides information that will be useful for the further study of L. hesperus saliva and Lygus – microbe interactions.