Identification and expression of nuclear receptor genes during nutritive phagocyte development in sea urchin Mesocentrotus nudus gonads

The role of the endocrine system during synthesis of the nutrients (e.g., proteins, lipids, polysaccharides) in the gonad in sea urchins is imperfectly understood. We identify genes encoding nuclear receptors (NRs) involved in the development of nutritive phagocytes of the sea urchin Mesocentrotus nudus, and investigate their gene expression patterns during this time. RNA-seq analysis was performed on immature gonads using a next-generation sequencer. A total of 7,651,421 quality-controlled reads obtained using an Ion PGM sequencer were assembled into 175,092 contigs. BLASTn analysis identified 20 NR genes potentially involved in the development of nutritive phagocytes. Expression analyses revealed levels of four NR genes to increase during the development of nutritive phagocytes. These results indicate that these 20 NR genes have physiological functions in gonadal growth, and that 4 NR genes mainly control the expression of genes involved in the synthesis and metabolism of proteins, lipids, and polysaccharides during cellular proliferation in sea urchin gonads.