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Title: Comparative Genomics- Identifying similarities and differences across three leafhopper vectors of Xylella fastidiosa

Author
item Hunter, Wayne
item Shelby, Kent
item HUNNICUTT, L - NC STATE UNIVERSITY
item MIZELL, R - UNIV. OF FLORIDA
item TIPPING, C - DELAWARE VALLEY COLLEGE
item Dang, Phat

Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Proceedings
Publication Acceptance Date: 11/12/2008
Publication Date: 12/15/2008
Citation: Hunter, W.B., Shelby, K., Hunnicutt, L.E., Mizell, R.F., Tipping, C., Dang, P.M. 2008. Comparative Genomics- Identifying similarities and differences across three leafhopper vectors of Xylella fastidiosa. In: Symposium Proceedings of the 2008 Pierce's Disease Control Program Research Symposium. December 15-18, 2008, San Diego, California, p. 16-21.

Interpretive Summary: Using comparative genomics permitted us to identify genes which are important to insect survival and reproduction. Leafhoppers are the second most important vectors of agricultural diseases, thus we examined the gene expression across three leafhopper leafhoppers, Homalodisca vitripennis, Graphocephala atropunctata, and Oncometopia nigricans, are vectors of the plant-infecting bacterium, Xylella fastidiosa. This bacterium causes Pierce’s disease of grapes and Scorch diseases in many other woody crops. Genomic data provides a new way to examine insect biology and also provides basic data to conduct evolutionary studies while expanding basic genetic information across members of the Hemiptera, plant sucking insects. Comparative approaches also advanced the specific understanding of leafhopper immunity, pathology, and development. The importance of these leafhoppers as vectors of Pierce’s disease, necessitates the development of abundant genetic sesquences for each. We produced and analyzed several cDNA libraries made from leafhopper adults, nymphs, salivary gland and midgut tissues, providing a genetic resource totaling approximately. 50,000 ESTs. When assembled we obtained approximately 5,000 specific transcripts for each species for comparison. This is approximately one-third of all the predicted active genes as proposed from other insect genomes which demonstrated approximately 15,000 total predicted genes. Examination of serine proteases, aminopeptidases, and cathepsins plus other enzymes showed significant homologies among and to other insects, further supporting previous phylogenetic analyses. Results showed a greater number of significant homology matches between the Homalodisca and Oncometopia leafhoppers than to Graphocephala. Analyses between these species to other known insect genomes demonstrated that the top 6 species homologies to insects whose genomes had been completed: Fruit Fly, two species of Mosquitoes, the stored grain beetle-Tribolium, and a parasitoid wasp-Nasonia, and the Honey bee. These genetic datasets provide the foundation for applications of gene disruption methodologies such as RNA interference. These new approaches will depend on the availability of genetic information to design highly specific and effective management tools to reduce either leafhopper populations and/or leafhopper-transmitted diseases.

Technical Abstract: Leafhoppers are the second most important vectors of agricultural diseases, thus we examined the gene expression across three leafhopper leafhoppers, Homalodisca vitripennis, Graphocephala atropunctata, and Oncometopia nigricans, which are vectors of the plant-infecting bacterium, Xylella fastidiosa. This bacterium causes Pierce’s disease of grapes and Scorch diseases in many other woody crops. Genomic data provides a new way to examine insect biology and also provides basic data to conduct evolutionary studies while expanding basic genetic information across members of the Hemiptera. Comparative approaches also advance specific understanding of leafhopper immunity, pathology, and development. The importance of these leafhoppers as vectors of Pierce’s disease, the abundance of ESTs produced for each, and their differences in host plant preferences, provide an excellent opportunity to conduct comparative examinations. We produced and analyzed several cDNA libraries made from leafhopper adults, nymphs, salivary gland and midgut tissues, providing a genetic resource totaling approximately. 50,000 ESTs. When assembled we obtained approximately 5,000 specific transcripts for each species for comparison. This is approximately one-third of all the predicted active genes as proposed from other insect genomes which demonstrated approximately 15,000 total predicted genes. Examination of serine proteases, aminopeptidases, and cathepsins plus other enzymes showed significant homologies among and to other insects, further supporting previous phylogenetic analyses. Results showed a greater number of significant homology matches between the Homalodisca and Oncometopia leafhoppers than to Graphocephala. Analyses between these species to other known insect genomes demonstrated that the top 6 species homologies to insects whose genomes had been completed: Drosophila melanogaster, Aedes aegyptii, Tribolium castaneum, Anopheles gambiae, Nasonia vitripennis, and Apis mellifera. A distribution across molecular functions of the transcripts gave the greatest number within: catalytic activity = 1,945; binding = 1,731; and transporter activity = 505 (Blast2GO analysis). These EST datasets provide the foundation for applications of gene disruption methodologies such as RNAi. These new approaches will depend on the availability of genetic information to design highly specific and effective management tools to reduce either leafhopper populations and/or leafhopper-transmitted diseases.