Jihoon Joa#, Jooseong Oha#, Hyun-Gwan Leeb, Hyun-Hee Honga, Sung-Gwon Leea, Seongmin Cheona, Elizabeth M. A. Kernc, Soyeong Jinc, Sung-Jin Chod*, Joong-Ki Parkc*, Chungoo Parka*
aSchool of Biological Sciences and Technology, Chonnam National University, Gwangju 61186, Republic of Korea
bMarine Ecological Disturbing and Harmful Organisms Research Center, Department of Oceanography, Chonnam National University, Gwangju 61186, Republic of Korea
cDivision of EcoScience, Ewha Womans University, Seoul 03760, Republic of Korea
dDepartment of Biology, College of Natural Sciences, Chungbuk National University, Cheongju, Chungbuk 28644, Republic of Korea
# These authors equally contributed this work.
*Corresponding Authors : Chungoo Park, Joong-Ki Park, Sung-Jin Cho
Background: The Japanese sea cucumber (Apostichopus japonicus Selenka 1867) is an economically important species as a source of seafood and ingredient in traditional medicine. It is mainly found off the coasts of northeast Asia. Recently, substantial exploitation and widespread biotic disease in A. japonicus have generated increasing conservation concern. However, the genomic knowledge base and resources available for researchers to use in managing this natural resource and to establish genetically based breeding systems for sea cucumber aquaculture are still in a nascent stage.
Findings: A total of 312 gigabases (Gb) of raw sequences were generated using the Illumina HiSeq 2000 platform and assembled to a final size of 0.66 Gb which is about 80.5% of the estimated genome size (0.82 Gb). We observed nucleotide-level heterozygosity within the assembled genome to be 0.986%. The resulting draft genome assembly comprising 132,607 scaffolds with an N50 value of 10.5 kb contains a total of 21,771 predicted protein-coding genes. We identified 6.6 - 14.5 million heterozygous SNPs in the assembled genome of the three natural color variants (green, red, and black), resulting in an estimated nucleotide diversity of 0.00146.
Conclusions: We report the first draft genome of A. japonicus and provide a general overview of the genetic variation in the three major color variants of A. japonicus. These data will help provide a comprehensive view of the genetic, physiological, and evolutionary relationships among color variants in A. japonicus, and will be invaluable resources for sea cucumber genomic research.
Keywords: Sea cucumber genome, Apostichopus japonicus, Color variants, Genetic variation, Population genomics