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The orange-spotted grouper, Epinephelus coioides, is one of the most popular fish in China and Southeast Asian countries because of its important economic value. However, molecular mechanism underlying the growth of orange-spotted grouper has never been fully understood. Herein, we performed a genome-wide association study (GWAS) on a natural population of 198 individuals aiming to screen the whole genome of orange-spotted grouper for identification of growth-related loci by restrictionsite associated DNA sequencing. In this research, 261,366 single nucleotide polymorphisms (SNPs) were developed, in which 110 SNPs were identified to be correlated with growth and 20 SNPs were further confirmed to be associated with both body weight and total length. From these identified SNPs, we annotated a total of 34 genes, including adgrb2, csnkza1, cers5, col22a1, creb5, dnd1, dzank1, dnai1, npy2r, fat3, lrrk2, lrp5, map3k9, and so on. Among these candidate genes, npy2r (neuropeptide Y receptor Y2) was reported to play a critical role in growth of the orange-spotted grouper. In addition, population structure, principal component analysis, kinship matrix and linkage disequilibrium were examined to verify the accuracy and reliability of our GWAS results. Our data will also provide a valuable genetic resource for further marker-assisted selection program to improve growth quality in groupers.

The tomato hind, Cephalopholis sonnerati, is a bottom-dwelling coral reef fish, which is widely distributed in the Indo-Pacific and Red Sea. C. sonnerati also features complex social structures and behaviour mechanisms. Here, we present a high-quality, chromosome-level genome assembly for C. sonnerati that was derived using PacBio sequencing and Hi-C technologies. A 1043.66 Mb genome with an N50 length of 2.49 Mb was assembled, produced containing 795 contigs assembled into 24 chromosomes. Overall, 97.2% of the complete BUSCOs were identified in the genome. A total of 26,130 protein-coding genes were predicted, of which 94.26% were functionally annotated. Evolutionary analysis revealed that C. sonnerati diverged from its common ancestor with E. lanceolatus and E. akaara approximately 41.7 million years ago. In addition, comparative genome analyses indicated that the expanded gene families were highly enriched in the sensory system. Finally, we found the tissue-specific expression of 8108 genes. We found that these tissue-specific genes were highly enriched in the brain. In brief, the high-quality, chromosome-level reference genome will provide a valuable genome resource for studies of the genetic conservation, resistance breeding, and evolution of C. sonnerati.

The red-spotted grouper (Epinephelus akaara) is one of the most commercially important aquatic species in China. However, its seedstock has low larval survival rates, and its stability is confronted with the danger of overexploitation. In this study, a high-density genetic map was constructed using 3435 single nucleotide polymorphisms (SNPs) from 142 first generation (F1) full-sib offspring and two parents of a red-spotted grouper population. The total genetic length of the map was 2300.12 cM with an average intermarker distance of 0.67 cM. Seventeen genome-wide significant quantitative trait loci (QTLs) for growth-related traits were detected on 24 linkage groups, including 5 QTLs for full length, 7 QTLs for body length, and 5 QTLs for body weight. The contribution values of explained phenotypic variance ranged from 10.7% to 12.9%. Moreover, 13 potential candidate genes for growth-related traits were identified. Collectively, these findings will be useful for conducting marker-assisted selection of the red-spotted grouper in future studies.