A high-density genetic linkage map and QTL mapping for growth and sex of yellow drum (Nibea albiflora).

A high-density genetic linkage map is essential for the studies of comparative genomics and gene mapping, and can facilitate assembly of reference genome. Herein, we constructed a high-density genetic linkage map with 8,094 SNPs selected from 113 sequenced fish of a F1 family. Ultimately, the consensus map spanned 3818.24 cM and covered nearly the whole genome (99.4%) with a resolution of 0.47 cM. 1,457 scaffolds spanning 435.15 Mb were anchored onto 24 linkage groups, accounting for 80.7% of the draft genome assembly of the yellow drum. Comparative genomic analyses with medaka and zebrafish genomes showed superb chromosome-scale synteny between yellow drum and medaka. QTL mapping and association analysis congruously revealed 22 QTLs for growth-related traits and 13 QTLs for sex dimorphism. Some important candidate genes such as PLA2G4A, BRINP3 and P2RY1 were identified from these growth-related QTL regions. A gene family including DMRT1, DMRT2 and DMRT3 was identified from these sex-related QTL regions on the linkage group LG9. We demonstrate that this linkage map can facilitate the ongoing marker-assisted selection and genomic and genetic studies for yellow drum.

Transcriptome-wide identification and functional investigation of circular RNA in the teleost large yellow croaker (Larimichthys crocea).

Circular RNA (circRNA) was first reported over thirty years ago. With the development of high-throughput sequencing technologies, circRNA has been identified in an increasing number of species. However, few studies on circRNA have been reported in teleost fish. Accumulating transcriptome and phenotype data enable us to probe the biological functions of circRNA in fish species. Here, we report the identification of circRNAs from RNA sequencing (RNA-seq) data in large yellow croaker (Larimichthys crocea), a commercially important marine fish in China and East Asia. Using the computational identification, 975 circular RNAs were detected, of which three were validated by experiments. GO and KEGG analyses revealed the biological functions of genes hosting the circRNAs were enriched in the progression of translation initiation, macromolecule metabolism and binding. Notably, we found that many circRNAs in large yellow croaker had abundant microRNA-binding sites. A total of 363 the identified circRNAs had more than five miRNA-binding sites, among which twenty-two had more than ten binding sites for the miRNA-430 and the let-7 family. Our study confirmed the presence of circRNAs in large yellow croaker for the first time, providing a valuable reference for circRNA identification in fish species. Meanwhile, this work confirmed that the RNA-seq data from the traditional linear transcriptome library could be used for preliminary circRNA identification, which may offer an important reference for preliminary circRNA investigations in other species.