Transcription profiling using RNA-Seq demonstrates expression differences in the body walls of juvenile albino and normal sea cucumbers Apostichopus japonicus

Sea cucumbers Apostichopus japonicus are one of the most important aquaculture species in China. Their normal body color is black to fi t their surroundings. Wild albinos are rare and hard to breed. To understand the differences between albino and normal(control) sea cucumbers at the transcriptional level, we sequenced the transcriptomes in their body-wall tissues using RNA-Seq high-throughput sequencing. Approximately 4.876 million(M) and 4.884 M 200-nucleotide-long cDNA reads were produced in the cDNA libraries derived from the body walls of albino and control samples, respectively. A total of 9 561(46.89%) putative genes were identifi ed from among the RNA-Seq reads in both libraries. After fi ltering, 837 signifi cantly differentially regulated genes were identifi ed in the albino library compared with in the control library, and 3.6% of the differentially expressed genes(DEGs) were found to have changed those more than fi ve-fold. The expression levels of 10 DEGs were checked by real-time PCR and the results were in full accord with the RNA-Seq expression trends, although the amplitude of the differences in expression levels was lower in all cases. A series of pathways were signifi cantly enriched for the DEGs. These pathways were closely related to phagocytosis, the complement and coagulation cascades, apoptosis-related diseases, cytokine-cytokine receptor interaction, and cell adhesion. The differences in gene expression and enriched pathways between the albino and control sea cucumbers offer control targets for cultivating excellent albino A. japonicus strains in the future.