Abstract
BackgroundThe medfly, Ceratitis capitata, is a highly invasive agricultural pest that has become a model insect for the development of biological control programs. Despite research into the behavior and classical and population genetics of this organism, the quantity of sequence data available is limited. We have utilized an expressed sequence tag (EST) approach to obtain detailed information on transcriptome signatures that relate to a variety of physiological systems in the medfly; this information emphasizes on reproduction, sex determination, and chemosensory perception, since the study was based on normalized cDNA libraries from embryos and adult heads.ResultsA total of 21,253 high-quality ESTs were obtained from the embryo and head libraries. Clustering analyses performed separately for each library resulted in 5201 embryo and 6684 head transcripts. Considering an estimated 19% overlap in the transcriptomes of the two libraries, they represent about 9614 unique transcripts involved in a wide range of biological processes and molecular functions. Of particular interest are the sequences that share homology with Drosophila genes involved in sex determination, olfaction, and reproductive behavior. The medfly transformer2 (tra2) homolog was identified among the embryonic sequences, and its genomic organization and expression were characterized.ConclusionThe sequences obtained in this study represent the first major dataset of expressed genes in a tephritid species of agricultural importance. This resource provides essential information to support the investigation of numerous questions regarding the biology of the medfly and other related species and also constitutes an invaluable tool for the annotation of complete genome sequences. Our study has revealed intriguing findings regarding the transcript regulation of tra2 and other sex determination genes, as well as insights into the comparative genomics of genes implicated in chemosensory reception and reproduction.
Highlights
The medfly, Ceratitis capitata, is a highly invasive agricultural pest that has become a model insect for the development of biological control programs
Generation and assembly of medfly embryo and head expressed sequence tag (EST) Two unidirectional, normalized cDNA libraries were constructed from embryos ranging in age from 30 min to 36 hr after oviposition and from adult male and female heads of flies ranging from 30 min to 8 days after emergence
EST libraries represent a rich source of polymorphic markers, be they SSRs or SNPs, that can be employed in high-throughput genotyping methods for population genetics and ecological studies [67]
Summary
The medfly, Ceratitis capitata, is a highly invasive agricultural pest that has become a model insect for the development of biological control programs. Its success as an invasive species is partially due to its unusually wide host range and its ability to adapt to a wide range of climatic conditions and habitats [1] As such, it has become the target of extensive control programs and a model organism for the sterile insect technique (SIT), a method considered to be among the most efficient and environmentally friendly control procedures [2,3]. Molecular genetics studies of the medfly began in the early 1990s, at present (January 2008) only 182 putative coding sequences are known, almost half of which are fragmentary [5] This lack of molecular data is in sharp contrast to the mass of data that has been accrued on the classical and population genetics of this model insect
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