De novo transcriptome Assembly of Four Potential Pierce’s Disease Insect Vectors from Arizona Vineyards

Pierce’s disease (PD) profoundly impacts wine and table grape production, resulting in tens of millions of US dollars lost annually in California alone. The pathogen responsible for PD, Xylella fastidiosa, is a xylem-limited bacterium that is transferred between plants by insects that feed on xylem sap, generally known as sharpshooters. Pierce’s disease is deadly to grape vines and the best preventative measure to mitigate plant infections is to manage the insect vectors. While PD is found in the southeastern United States and Mexico, PD has recently been identified in Arizona’s grape growing regions which span the entire state and include the Verde Valley, Wilcox, and Sonoita. For this study, four potential insect vectors for PD in Arizona were identified: Cuerna arida (desert leafhopper), Graphocephala atropunctata (bluegreen sharpshooter), Homalodisca liturata (smoketree sharpshooter), and Clastoptera arizonana (spittlebug). To gain insight on enzyme production and transcript diversity in these xylem feeding insects, de novo transcriptomes of the four species were assembled using a Trinity based pipeline. The transcriptomes averaged around 97K transcripts, with an average contig length of 1Kb. To measure the robustness of the assembly, BUSCO was used to estimate the completeness of the assemblies and the total complete single-copy BUSCO’s ranged from 60%-82%. The transcriptomes were BLASTed against a bacterial nr database to determine which bacteria are present in each species. The results of our analyses are critical for developing specific, targeted practices to manage these pest species and to prevent the spread of PD in vineyards.