Identification of ovarian gene expression patterns during oocyte growth in Atlantic cod (Gadus morhua)

Although the United States is a major seafood consumer, we grow only a fraction of what we consume, and the U.S. trade deficit in seafood ranks second behind oil at over ;To further characterize the expression patterns throughout oocyte growth, genes from cod vitellogenic growth stage libraries were also combined with previously identified genes during early growth in coho salmon (Oncorhynchus kisutch) in a 50 gene QPCR survey, ranging from the onset of primary growth (oocyte differentiation) to late vitellogenesis. Most expression patterns could be grouped into three major clusters, consisting of oocyte-derived (cluster 1) and likely follicle cell (clusters 2 and 3) genes. Oocyte genes were elevated during primary growth, while many follicle cell transcripts were abundant during oocyte differentiation and vitellogenesis. Few expression changes previously identified in coho salmon were evident in cod, which is likely due to differences in reproductive strategies. The novel expression patterns identified in the present studies provide new information on teleost oocyte growth, that may be used in the development of future genetic markers for evaluating egg quality in aquaculture.