Gonadal transcriptomic analysis and identification of candidate sex-related genes in Mesocentrotus nudus

The edible sea urchin, Mesocentrotus nudus, is both an economically important mariculture species and an excellent model for studying reproductive development. The gonads are the only edible parts of sea urchins and increasing market demand for high-quality gonads has prompted increasing amounts of research into the molecular mechanisms of reproduction. Using a high-throughput sequencing technology, we performed transcriptome sequencing on the gonads of females and males, sampled before the spawning season, to identify genes involved in sex determination, sex differentiation and gametogenesis. Through a de novo transcriptome assembly approach, we obtained 104,039 unigenes, of which 40,471 (38.90%) showed homologies with known proteins in public databases. By comparing the expression levels of these unigenes in females and males, 15,368 differentially-expressed unigenes (DEGs) were identified. Compared with males, 9473 were up-regulated and 5895 were down-regulated in females. Multiple candidate genes were identified that may play important roles in spermatogenesis, oogenesis, and germ cell development. Furthermore, we identified and characterized several genes involved in sex determination and sex differentiation, such as dmrt1 and foxl2. The current study provides valuable molecular resources for studying the underlying mechanisms of reproduction in sea urchins.