Expressed sequence tag (est)-based characterization of gene regulation in artemia larvae

Sequencing of cloned cDNAs to produce expressed sequence tag (EST) libraries is an efficient method for gene identification and analysis of transcription status within organisms. In this context, an EST library containing 609 sequences was constructed using cDNA from emerged larvae of the brine shrimp, Artemia franciscana, a developmental stage within this crustacean that has received limited attention at the molecular level. Three hundred and forty-eight ESTs exhibited similarity to database sequences of known function. Twenty sequences matched hypothetical open reading frames of unknown function, while 163 clones were unlike any archived database sequences and some of these may represent unidentified genes. Of the ESTs that encode proteins of known function, those participating in metabolic activities and protein/gene expression were the most numerous. Proteins involved in mitochondrial function and ribosome assembly were particularly prominent within these two functional categories. Other ESTs with multiple representatives in the library included those encoding actin, a selection of ion transporters, and proteins used in exoskeleton construction. Transcripts encoding proteins required for cell division were rare, suggesting that the number of dividing cells in emerged larvae is small. The data generated in this study significantly increase the scope of Artemia cDNA sequences in the public domain, and furnish a qualitative assessment of functional and biosynthetic activities within emerged Artemia larvae.