Submitted to: XXI International Congress of Entomology, Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/14/2008
Publication Date: 7/6/2008
Citation: Backus, E.A., Morgan,, D. 2008. Time course of colonization of the glassy-winged sharpshooter precibarium by Xylella fastidiosa provides evidence for two types of egestion during inoculation. Abstract No. 1584. In: Proceedings of the XXIII International Congress of Entomology CD, in Durban, South Africa, July 6-12, 2008. Interpretive Summary:
Technical Abstract: Introduction of the glassy-winged sharpshooter (GWSS) into California has caused an increase in incidence of Pierce’s Disease in grape-growing regions. Although host plant resistance to the causative bacterium, Xylella fastidiosa, and/or its GWSS vector is being sought, research is hampered by lack of understanding of the acquisition and inoculation process. X. fastidiosa (Xf) is acquired into and colonizes the anterior foregut of the vector (the precibarium and cibarium), and is inoculated back into the plant from this area during a part of the feeding process previously unknown. To study the location of acquisition (from which inoculation occurs), we developed a confocal laser scanning microscopy method to visualize in situ green fluorescent protein (GFP)-transformed Xf within the undissected foregut of the vector. Fine structure of the colonies was then examined via scanning electron microscopy. We performed a time course study of GFP-Xf acquisition by GWSS, across acquisition access periods (AAP) ranging from 1 to 14 days. Bacterial colonies form in the cibarium within the first 24 hrs of AAP; at the same time, they begin to move forward from this cibarial reservoir into the precibarium. By AAP day 3, bacteria line the length of the precibarium except the area of the D-sensilla field (below the precibarial valve), which is almost always kept free of bacteria. By AAP day 5, this large accumulation of bacteria has disappeared, and evidence suggests that the precibarium was physically swept clear of biofilm. After day 5, this cycle of loading above the valve then discharging starts again. We hypothesize that there are two types of egestion (injection of material from the anterior foregut back into the plant): rinsing egestion (continuously occurring from below the valve) and discharging egestion (sporadically [every 3 to 5 days] occurring from above the valve).