Comprehensive EST analysis of Atlantic halibut (Hippoglossus hippoglossus), a commercially relevant aquaculture species

Background: An essential first step in the genomic characterisation of a new species, in this case Atlantic halibut ( Hippoglossus hippoglossus), is the generation of EST information. This forms the basis for subsequent microarray design, SNP detection and the placement of novel markers on genetic linkage maps. Results: Normalised directional cDNA libraries were constructed from five different larval stages ( hatching, mouth- opening, midway to metamorphosis, premetamorphosis, and postmetamorphosis) and eight different adult tissues ( testis, ovary, liver, head kidney, spleen, skin, gill, and intestine). Recombination efficiency of the libraries ranged from 91 - 98% and insert size averaged 1.4 kb. Approximately 1000 clones were sequenced from the 5'- end of each library and after trimming, 12675 good sequences were obtained. Redundancy within each library was very low and assembly of the entire EST collection into contigs resulted in 7738 unique sequences of which 6722 ( 87%) had matches in Genbank. Removal of ESTs and contigs that originated from bacteria or food organisms resulted in a total of 7710 unique halibut sequences. Conclusion: A Unigene collection of 7710 functionally annotated ESTs has been assembled from Atlantic halibut. These have been incorporated into a publicly available, searchable database and form the basis for an oligonucleotide microarray that can be used as a tool to study gene expression in this economically important aquacultured fish.