Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Proceedings
Publication Acceptance Date: 12/7/2010
Publication Date: 12/15/2010
Citation: Hunter, W.B., Bextine, B.R., Welch, E.W., Tipping, C., Mizell, R., Katsar, C.S. 2010. Delta-9 Desaturase from Sharpshooters. 2010 Proceedings of the Pierce's Disease Research Symposium, California Food and Agriculture, December 15-17, 2010, San Diego, California. p. 20-23. Interpretive Summary: The leafhopper delta 9 desaturase transcript was identified. The identification of genes which are critical for the survival and reproduction of insect pests opens the door for applications of natural insect management based on gene disruption, such as RNA interference, RNAi. Desaturase enzymes in leafhoppers are needed to digest food, store fats, and produce eggs. Sequencing and identification are the first steps towards development of safe, specific, insect management based upon the genetics of leafhoppers. The glassy-winged sharpshooter causes economic losses to growers by spreading Pierce’s disease of grapevine, which can stop grape production and kill vines. Developments of effective population management strategies are needed. Insecticides although successful to reduce the economic impact of these insects, ultimately will result in resistance and/or resurgence of secondary pests. Thus alternative methods of population suppression are continually being developed. Here we propose the use of gene targeting against the desaturases to reduce the ability of leafhoppers to grow and reproduce.
Technical Abstract: Genomic analyses of several leafhoppers identified the first leafhopper delta-9 desaturase. Identification of important gene transcripts within insect pests permits them to be targeted with RNA interference, RNAi, strategies. The glassy-winged sharpshooter, GWSS (Hemiptera: Cicadellidae; Homalodisca vitripennis) and other leafhoppers are vectors of Xylella fastidiosa, a xylem-limited bacteria that causes economic loss in grapevine and other woody agricultural fruit, nut, and ornamental crops. Management of Pierce’s disease currently depends heavily upon insecticides. To extend current IPM programs alternatives need to be developed which can work within these programs. The GWSS desaturase cDNA encodes a 367 protein with 71% identity to Acheta domesticus desaturase, and greater than 50% identity with other insect delta 9 desaturases. In silico analyses places GWSS delta 9 desaturase in the Family 1 of ProDomain fatty acid desaturases and predicts the protein is a Palmitoyl-CoA delta 9 desaturase-1 (accession number: AY588067). Expression analyses resulted in lack of detection of expression in eggs. All instars, 1-5th, expressed delta 9 desaturase showing a significant increase in the 5th instar and adults which correlated to increased feeding on a widening host plant range to complete development. There was no significant difference in expression levels among 1-4th instars. The 5th instars had significantly increased levels of desaturase from previous instars, while adults expressed significantly greater levels from all other life stages. Adult females showed a greater than 7 fold increase over 1-4th instars, with a greater than 3 fold increase over 5th instars. There was no significant difference to adult males. This is the first desaturase identified from leafhoppers and builds upon our understanding of the biological pathways in leafhopper fitness.