Gene discovery and functional genomics in Tephritids: a tool for improving pest control.

Using a functional genetics approach, based on Expressed Sequence Tags (ESTs) and microarray technologies, this research programme aims to identify genes involved in biologically important processes such as development, sex determination and mate and host recognition in the model species C. capitata (Mediterranean fruit fly). This gene discovery study will thus represent a unique opportunity to explore the molecular bases of these biological traits in this pest species. We have initiated a gene discovery project to provide information on the expression and regulation of the medfly. To this end, we have created expressed sequence tags (ESTs) and oligonucleotide microarrays for the medfly embryo and adult head. Over 24,000 cDNA clones were partially sequenced from two normalised cDNA libraries resulting in more than 20,000 high quality ESTs with an average length of 700 bp. After assembly, the embryo sequences gave rise to a total of 5201 putative transcripts. BLASTX analyses against the non-redundant (nr) protein database resulted in best-hits (e less than 10-5) in 75% of the assembled sequences. The majority of the best-hits were against arthropod sequences (97%) and in particular Drosophila species (90%). The medfly ESTs were annotated with respect to D. melanogaster. Almost 52% (2699) of the embryonic assembled sequences were assigned a Gene Ontology (GO) classification based on the annotation of the best hit D. melanogaster peptide obtained in BLASTX searches. The embryo ESTs represent a broad range of molecular functions and biological processes. Oligonucleotide microarrays have been constructed to represent over 12,000 embryo and head EST cDNA clones. The genes identified and the analyses of their expression patterns will lead to an increase in the basic knowledge on biology of this invasive pest insect. This knowlege will improve our ability to understand the potential risks associated with spread of this insect. In the long term, the results of the study will aid the development of more efficient strategies for the detection, monitoring and control of this species in the context of programmes such as the Sterile Insect Technique (SIT). Furthermore, as the medfly represents a model species for other true fruit flies of the genera Ceratitis, Bactrocera, Dacus and Anastrepha, many of which are also serious agricultural pests, the extension of the information obtained from this study will be of enormous value not only for the development of control strategies, but also comparative evolutionary studies.