Comparative Behavioral and Protein Study of Salivary Secretions in Homalodisca spp. Sharpshooters (Hemiptera: Cicadellidae: Cicadellinae)

Abstract

A novel brush-induced method to physically stimulate salivation was applied to the glassy-winged and smoke tree sharpshooters (Hemiptera: Cicadellidae: Cicadellinae). This technique enabled the direct observation of salivary secretion processes, solidification of saliva, and 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 brushinduced saliva collection method has merit for future biochemical analyses of saliva. The implications of this work could potentially include illuminating the mechanism of inoculation by the Pierce's disease bacterium, Xylella fastidiosa.

Formation of Stylet Sheaths in āere (in air) from Eight Species of Phytophagous Hemipterans from Six Families (Suborders: Auchenorrhyncha and Sternorrhyncha)

“…As referenced previously, prior work has implied in āere solidified sheath material occurring in sharpshooters [29]. In this prior study, the authors indicate specific protein differences between the profiles of brush induced sheath materials and sheath materials harvested by differing methods (parafilm collected over diet, direct gland removal saliva harvest, and filter paper extracts ‘milking’).…”

“…In this prior study, the authors indicate specific protein differences between the profiles of brush induced sheath materials and sheath materials harvested by differing methods (parafilm collected over diet, direct gland removal saliva harvest, and filter paper extracts ‘milking’). Their data indicated the necessity of protein factors for full stylet sheath formation to occur [29]. Other hypotheses suggest that oxygen specific interactions are needed for proper sheath gelling [11] and support for this has recently been indicated for aphid stylet sheaths [10].…”

“…This is subsequently followed by a thicker sheath ‘trunk’ having a continuous sequential bulbous structure as it traverses the tissue to the target vascular region (phloem or xylem) where the sheath may remain as a single channel or branch laterally throughout the vascular tissue, also in a continuous sequential bulbous form [22], [27], [28]. Recently, sheath material was induced using a brushing technique in sharpshooter [29]; however, the shape of this induced solidified sheath material differs from those formed naturally [30], [31].…”

Sharpshooters: a review of what moves Xylella fastidiosa

“…Gelling saliva is composed of lipoproteins and phospholipids that are in liquid phase when initially secreted but harden rapidly to form a salivary sheath that encases the stylets (Alhaddad et al . ). The second type of saliva is watery (or digestive) saliva.…”

Lessons from One Fastidious Bacterium to Another: What Can We Learn about Liberibacter Species from Xylella fastidiosa

“…The authors speculate that this protein may be trafficked from the hemolymph to the salivary glands and subsequently the salivary sheath. Future research should focus on identifying these proteins via modern proteomics techniques and targeting them to inhibit H. vitripennis feeding [143].…”