Genome-wide analysis of redox-regulated genes in a dinoflagellate

In this study, the effects of 1 mM sodium nitrite, a reactive nitrogen species (RNS) generator, and 0.5 mM paraquat, which produces reactive oxygen species (ROS), on gene expression in the marine dinoflagellate species Pyrocystis lunula were investigated using microarrays containing 3500 complementary DNAs (cDNAs). A total of 246 differentially expressed genes were identified under these treatments: 204 genes were specifically regulated in response to nitrite and 37 genes specifically to paraquat. Only six genes showed a dependence on both nitrite and paraquat, indicating that the two agents act predominantly via distinct pathways. Although many of these redox-regulated genes encode proteins from a diverse range of functional categories, the majority of them (68%) represent novel sequences. Temporary abnormal spherical cells occurred in nitrite-treated cultures, but not in those exposed to paraquat, suggesting that this response involves a specific pathway triggered by RNS. The genes involved include one that encodes a transcription factor unique to dinoflagellates (HPl), and genes encoding proteins similar to those regulating developmental processes in plants and animals such as NYD-SP5, shaggy and calcium-dependent kinases, the COP9 signalosome complex, ubiquitin-related proteases and a metacaspase.