RESUMEN
Hypoxic events affecting aquatic environments have been reported worldwide and the hypoxia caused by eutrophication is considered one of the serious threats to coastal marine ecosystems. To investigate the molecular-level responses of marine organisms exposed to oxygen depletion stress and to explore the differentially expressed genes induced or repressed by hypoxia, differential display polymerase chain reaction (DD-PCR) was used with mRNAs from the marine mussel, Mytilus galloprovincialis, under oxygen depletion and normal oxygen conditions. In total, 107 cDNA clones were differentially expressed under hypoxic conditions relative to the control mussel group. The differentially expressed genes were analyzed to determine the effects of hypoxia. They were classified into five functional categories: information storage and processing, cellular processes and signaling, metabolism, predicted general function only, and function unknown. The differentially expressed genes were predominantly associated with cellular processing and signaling, and they were particularly related to the signal transduction mechanism, posttranslational modification, and chaperone functions. The observed differences in the DD-PCR of 10 genes (encoding elongation factor 1 alpha, heat shock protein 90, calcium/calmodulin-dependent protein kinase II, GTPase-activating protein, 18S ribosomal RNA, cytochrome oxidase subunit 1, ATP synthase, chitinase, phosphoglycerate/bisphosphoglycerate mutase family protein, and the nicotinic acetylcholine receptor) were confirmed by quantitative RT-PCR and their transcriptional changes in the mussels exposed to hypoxic conditions for 24-72 h were investigated. These results identify biomarker genes for hypoxic stress and provide molecular-level information about the effects of oxygen depletion on marine bivalves.