Submitted to: Annals of the Entomological Society of America
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/31/2011
Publication Date: 5/1/2011
Citation: Alhaddad, H., Coudron, T.A., Backus, E.A., Schreiber, F. 2011. Comparative behavioral and protein study of salivary secretions in Homalodisca spp. sharpshooters (Hemiptera: Cicadellidae: Cicadellinae). Annals of the Entomological Society of America. 104:543-552. Interpretive Summary: Insects can be responsible for spreading plant diseases by picking up the microbial that causes the disease while feeding on an infected plant and then delivering the microbial to the next plant that it feeds on. The mouth parts and saliva of the insect are thought to be involved in the transmission process but that involvement is not well understood. This study investigated three insects that have similar mouth parts but differ in their ability to vector a devastating disease of grapes. A novel method was discovered for stimulating salivation in these insects which allowed for the collection of saliva in its natural form. The insects that transmit the disease produced both a liquid and gel form of saliva while insects that do not transmit the disease produced only a gel form of saliva. Additionally, a unique set of proteins were found associated with those insects that were able to transmit the disease. These findings indicate that the liquid form and specific proteins of insect saliva may be prerequisites to insects spreading plant diseases. That information is valuable to producers and agribusinesses in understanding insect transmission of plant diseases and also to researchers in designing methods to control the spread of these diseases by insects.
Technical Abstract: A novel brush-induced method to physically stimulate salivation was applied to the glassy-winged and smoke tree sharpshooters. This technique enabled the direct observation of salivary secretion processes, solidification of saliva and for collection of salivary secretions. For both species, brush-induced saliva was first secreted in liquid form, a portion of which gradually solidified to form the salivary sheath for both sharpshooter species. Proteins of similar molecular weight were obtained from brush-induced saliva extracts from both sharpshooters. Extracts from dried sheaths collected from parafilm membranes over artificial diet had a different protein profile from brush-induced saliva extracts. The latter contained fewer proteins than extracts of the liquid content of salivary glands. Two proteins appeared in all three of the extracts from hemolymph, salivary glands, and brush-induced saliva, one of which also appeared in dried sheath extracts. Our findings support previous research by others, that there is a limited flow of protein from hemolymph to salivary glands and brush-induced saliva. There is also some protein modification associated with saliva solidification. The quantity and composition of proteins suggest the brush-induced saliva collection method has merit for future biochemical analyses of saliva. The implications of this work could potentially include illuminating the inoculation process by the Pierce’s disease bacterium, Xylella fastidiosa.