Submitted to: Journal of Applied Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/27/2015
Publication Date: 2/13/2016
Citation: Rogers, E.E. 2016. Deep 16sRNA sequencing of anterior foregut microbiota from the blue-green sharpshooter (Graphocephala atropunctata). Journal of Applied Entomology. 140:801-805. Interpretive Summary: Xylella fastidiosa (Xf) is a bacterium that causes a number of different leaf-scorching diseases of agronomically important plants, including Pierce’s disease of grapevine, almond leaf scorch disease, and citrus variegated chlorosis. The Xf bacterium is transmitted from one plant to another by sharpshooter insects. If a sharpshooter ingests fluid from an infected plant, bacteria will also be taken up and can stick in the sharpshooter’s oral cavity and multiply. Any sharpshooter already containing Xf can deposit bacterial cells into a previously healthy plant during feeding, thereby spreading Xf and increasing disease incidence. The principal native vector in coastal California is the blue-green sharpshooter (BGSS). Very little is known about the details of how Xf bacterial cells stick to the BGSS oral cavity. It is possible that other bacteria, ones that do not cause disease in plants, are also present in the oral cavity and may either help Xf cells stick or keep Xf cells from sticking. A DNA-sequence based method was used to inventory all bacterial species present in and around the oral cavity of 24 individual colony-raised BGSS. A large number of bacterial species previously known to be associated with insects, plants, and/or soils were detected; many, but not all, of these bacteria were also previously reported to be present in glassy-winged sharpshooters. This work is a necessary first step before testing for positive and negative interactions between Xf and other oral cavity bacteria.
Technical Abstract: Graphocephala atropunctata (Signoret) (Hemiptera: Cicadellidae) or the blue-green sharpshooter (BGSS) has been long recognized as the principal native vector of Xylella fastidiosa in coastal, wine-grape growing areas of California. X. fastidiosa is the causative agent of Pierce’s disease of grapevine and numerous other leaf-scorching diseases of agronomically important plants. X. fastidiosa has been shown to colonize the cibarium and pre-cibarium (anterior foregut) of sharpshooters, where it may encounter other naturally-occurring bacterial species. Here, deep 16S rRNA sequencing was used to survey the microbiota associated with the BGSS anterior foregut. DNA was extracted from dissected cibaria and pre-cibaria; a portion of the 16S rRNA gene was amplified and sequenced using Illumina MiSeq technology. An average of approximately 32,000 sequence reads per insect was obtained. Agrobacterium was the most common genus detected; additional sequencing of the full-length 16S rRNA gene further identified this as Agrobacterium tumefaciens or A. fabrum. A number of additional plant-associated bacterial genera were also detected (Pseudomonas, and Ensifer), along with genera known to be associated with insects (Baumannia) and soil (Stenotrophomonas, Caulobacter, Delftia, Achromobacter, Acinetobacter, and Novosphingobium). Approximately half of the genera reported here have been previously reported to be prevalent in the cibarium and pre-cibarium of glassy-winged sharpshooter (GWSS; Homalodisca vitripennis). Development of this comprehensive list is a necessary first step before evaluating interactions between X. fastidiosa and other bacteria present in sharpshooter cibarium and pre-cibarium.