- 12-EXPRESSED SEQUENCE TAGS FROM THE BLACK-WINGED SHARPSHOOTER : APPLICATION TO BIOLOGY AND VECTOR CONTROL Project

The black-winged sharpshooter, Oncometopia nigricans Walker, is considered a highly competent vector of several strains of the xylem-inhabiting bacterium Xylella fastidiosa (Xf), the causal agent of a number of economically important plant diseases including Pierce’s disease, phony peach disease, plum leaf scald and periwinkle wilt. To better understand the biology of the this leafhopper on a molecular level, our lab undertook a large-scale 5' end expressed sequence tag (EST) sequencing project of cDNA clones derived from O. nigricans adults. Similar EST sequencing projects from other insect pests have definitively proven their worth in answering biological questions relating to organismal behavior, development and physiology. These data enables the identification of target genes with potential for development of novel genomics-based management strategies to reduce leafhopper impacts on agricultural crops. To that end, we report on our advances on leafhopper genomic research involving a vector of Pierce’s disease, the sharpshooter, O. nigricans. We produced a dataset containing 4,411 high-quality ESTs, representing a set of 3,301 transcripts. Assembly identified 14 full length transcripts which have important biological functions. Research centering around the annotation, characterization, and application of the genomic information is demonstrated by work on a delta 9 desaturase and an Imaginal Disc Growth Factor, IDGF, isolated from O. nigricans. The sequences reported in this paper have been submitted to NCBI’s dbEST under the following accession numbers: DR755012DR759538 INTRODUCTION Sharpshooter leafhoppers (Cicadellidae) are vectors of a number of destructive plant diseases. Although the glassy-winged sharpshooter, GWSS, Homalodisca vitripennis Germar, is the most notorious of these vectors due to its detrimental impacts to commercial crops in California, a second leafhopper commonly referred to as the black-winged sharpshooter, Oncometopia nigricans Walker, has also been associated with pathogen transmission. Like GWSS, O. nigricans is a highly polyphagous xylem-feeding leafhopper present throughout the southeastern United States (Tipping et al., 2004). Upon feeding, bacteria are taken up into the insect’s mouthparts where they attach to the walls of the cibarium (Brlansky et al., 1983). During subsequent feedings, the bacteria are released into the plant. The transfer of xylem-inhabiting bacteria, including various Xf Wells pathotypes, is the cause of several economically important diseases including Pierce’s disease (PD) of grape, phony peach disease, plum leaf scald, and periwinkle wilt. In addition, O. nigricans has the ability to vector citrus variegated chlorosis (CVC) Xylella sp. to citrus with a transmission rate of 20.3%, a much greater efficiency than most other species tested to date (Brlansky et al., 2002). These findings demonstrate the importance of O. nigricans as a vector species with significant implications for the sustainability of Florida’s citrus industry. The importance of having genomic information generated from expressed sequence tag, EST, studies has been definitively demonstrated through such studies as Drosophila, Honey bee, and other organisms. Production of genomic information on O. nigricans which is now available (Hunter et al., NCBI) which was derived from single-pass sequencing of cDNA clones prepared from this sharpshooter and provides an invaluable resource for the identification of genes associated with the biology of the adult life stage. Annotation of the resultant dataset will also help in the identification of the gene/enzyme pathways involved in processes such as insect pathogen and insect-plant interactions. The availability of genomic data on O. nigricans provides the scientific community a foundation for future studies in functional genomics, and provides the genetic basis for tool development to advance creation of novel genomics-based management strategies for this and other leafhopper vectors of plant diseases. To that end, herein we report on full-length transcripts of 14 putative proteins, and the annotation of a dataset produced from O. nigricans and show their potential for quantification of global gene expression patterns, functional and comparative genomics studies.