Gap-free telomere-to-telomere genome assembly of marbled flounder (Pseudopleuronectes yokohamae).

Marbled flounder (Pseudopleuronectes yokohamae) is becoming a commercially important flatfish species in Northeast Asia due to its strong environmental adaptability and excellent nutritional value. However, no high-quality marbled flounder reference genome was reported to date, which greatly limits the studies of evolutionary and functional genomics. Here, we reported the first gap-free T2T genome in flatfish (marbled flounder), with length of 582.73 Mb (contig N50: 26.29 Mb) combing short reads, PacBio HiFi long reads, ONT ultra-long reads, and Hi-C data. All of the genome sequences were assembled onto 24 chromosomes, and 48 telomeres were identified on both ends of all chromosomes. 99.29% complete BUSCOs were identified, demonstrating a high level of completeness. The average mapping ratio of short reads, PacBio HiFi reads, and ONT ultra-long reads aligned to the genome was more than 99.89%. 121.02 Mb repeating elements and 22,778 protein-coding genes were identified in the genome assembly. These results provide valuable resources for the evolutionary genomics research and the identification of key candidate genes for economic traits in marbled flounder.