Primary genome scan for complex body shape-related traits in the common carp Cyprinus carpio

Genome-Wide Association Study of Body Shape-Related Traits in Large Yellow Croaker (Larimichthys crocea)

Large yellow croaker (Larimichthys crocea) is one of the most important cultured marine fish on the southeast coast of China. Its body shape is important for the aquaculture industry since it affects the behavior such as swimming, ingesting, and evading, as well as customer preference. Due to the greater consumer demand of small head, slender body large yellow croaker, selecting and breeding of slender individuals with the assistance of genetic markers will benefit the industry quickly. In this study, several traits were employed to represent body shape, including body depth/body length (BD/BL), body thickness/body length (BT/BL), caudal peduncle depth/caudal peduncle length (CPDLR), tail length/body length (TL/BL), and body area/head area (BA/HA). Genome-wide association study was conducted with a panmictic population of 280 individuals to identify SNP and genes potentially associated with body shape. A set of 20 SNPs on 12 chromosomes were identified to be significantly associated with body shape-related traits. Besides, 5 SNPs were identified to be suggestive associated with CPDLR and BT/BL. Surrounding these SNPs, we found some body shape-related candidate genes, including fabp1, acrv1, bcor, mstn, bambi, and neo1, which involved in lipid metabolism, TGF-β signaling, and BMP pathway and other important regulatory pathways. These results will be useful for the understanding of the genetic basis of body shape formation and helpful for body shape controlling of large yellow croaker by using marker-assisted selection.

A high-resolution genetic linkage map and QTL fine mapping for growth-related traits and sex in the Yangtze River common carp (Cyprinus carpio haematopterus)

Background

A high-density genetic linkage map is essential for QTL fine mapping, comparative genome analysis, identification of candidate genes and marker-assisted selection for economic traits in aquaculture species. The Yangtze River common carp (Cyprinus carpio haematopterus) is one of the most important aquacultured strains in China. However, quite limited genetics and genomics resources have been developed for genetic improvement of economic traits in such strain.

Results

A high-resolution genetic linkage map was constructed by using 7820 2b-RAD (2b-restriction site-associated DNA) and 295 microsatellite markers in a F2 family of the Yangtze River common carp (C. c. haematopterus). The length of the map was 4586.56 cM with an average marker interval of 0.57 cM. Comparative genome mapping revealed that a high proportion (70%) of markers with disagreed chromosome location was observed between C. c. haematopterus and another common carp strain (subspecies) C. c. carpio. A clear 2:1 relationship was observed between C. c. haematopterus linkage groups (LGs) and zebrafish (Danio rerio) chromosomes. Based on the genetic map, 21 QTLs for growth-related traits were detected on 12 LGs, and contributed values of phenotypic variance explained (PVE) ranging from 16.3 to 38.6%, with LOD scores ranging from 4.02 to 11.13. A genome-wide significant QTL (LOD = 10.83) and three chromosome-wide significant QTLs (mean LOD = 4.84) for sex were mapped on LG50 and LG24, respectively. A 1.4 cM confidence interval of QTL for all growth-related traits showed conserved synteny with a 2.06 M segment on chromosome 14 of D. rerio. Five potential candidate genes were identified by blast search in this genomic region, including a well-studied multi-functional growth related gene, Apelin.

Conclusions

We mapped a set of suggestive and significant QTLs for growth-related traits and sex based on a high-density genetic linkage map using SNP and microsatellite markers for Yangtze River common carp. Several candidate growth genes were also identified from the QTL regions by comparative mapping. This genetic map would provide a basis for genome assembly and comparative genomics studies, and those QTL-derived candidate genes and genetic markers are useful genomic resources for marker-assisted selection (MAS) of growth-related traits in the Yangtze River common carp.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4613-1) contains supplementary material, which is available to authorized users.

Mapping of quantitative trait loci associated with size, shape, and parr mark traits using first- and second-generation backcrosses between European and North American Atlantic salmon (Salmo salar)

Little is known about the genetic architecture of traits important for salmonid restoration ecology. We mapped quantitative trait loci (QTL) using single nucleotide polymorphisms (SNPs) for juvenile body length, weight, shape, and vertical skin pigmentation patterns (parr marks) within three hybrid backcross families between European and North American subspecies of Atlantic salmon. Amounts of variation in skin colour and pattern quantified in the two second-generation transAtlantic families exceeded the ranges seen in purebred populations. GridQTL analyses using low-density female-specific linkage maps detected QTL showing experiment-wide significance on Ssa02, Ssa03, Ssa09, Ssa11, Ssa19, and Ssa26/28 for both length and weight; on Ssa04 and Ssa23 for parr mark number; on Ssa09 and Ssa13 for parr mark contrast; and on Ssa05, Ssa07, Ssa10, Ssa11, Ssa18, Ssa23, and Ssa26/28 for geometric morphometric shape coordinates. Pleiotrophic QTL on Ssa11 affected length, weight, and shape. No QTL was found that explained more than 10% of the phenotypic variance in pigmentation or shape traits. Each QTL was approximately positioned on the physical map of the Atlantic salmon genome. Some QTL locations confirmed previous studies but many were new. Studies like ours may increase the success of salmon restoration projects by enabling better phenotypic and genetic matching between introduced and extirpated strains.

Quantitative trait loci for morphometric traits in multiple families of common carp (Cyprinus carpio)

Quantitative trait locus (QTL) mapping is frequently used to understand the genetic architecture of quantitative traits. Herein, we performed a genome scan for QTL affecting the morphometric characters in eight full-sib families containing 522 individuals using different statistical methods (Sib-pair and half-sib model). A total of 194 QTLs were detected in 25 different regions on 10 linkage groups (LGs). Among them, 37 QTLs on five LGs (eight, 13, 24, 40 and 45) were significant (5% genome-wide level), while the remaining 40 (1% chromosome-wide level) and 117 (5% chromosome-wide level) indicated suggestive effect on those traits. Heritabilities for most morphometric traits were moderate to high, ranging from 0.21 to 0.66, with generally strong phenotypic and genetic correlations between the traits. A large number of QTLs for morphometric traits were co-located, consistent with their high correlations, and may reflect pleiotropic effect on the same genes. Biological pathways were mapped for possible candidate genes on QTL regions. One significantly enriched pathway was identified on LG45, which had a P-value of 0.04 and corresponded to the "regulation of actin cytoskeleton pathway". The results are expected to be useful in marker-assisted selection (MAS) and provide valuable information for the study of gene pathway for morphometric and growth traits of the common carp.

QTL variations for growth-related traits in eight distinct families of common carp (Cyprinus carpio)

BACKGROUND

Comparing QTL analyses of multiple pair-mating families can provide a better understanding of important allelic variations and distributions. However, most QTL mapping studies in common carp have been based on analyses of individual families. In order to improve our understanding of heredity and variation of QTLs in different families and identify important QTLs, we performed QTL analysis of growth-related traits in multiple segregating families.

RESULTS

We completed a genome scan for QTLs that affect body weight (BW), total length (TL), and body thickness (BT) of 522 individuals from eight full-sib families using 250 microsatellites evenly distributed across 50 chromosomes. Sib-pair and half-sib model mapping identified 165 QTLs on 30 linkage groups. Among them, 10 (genome-wide P <0.01 or P < 0.05) and 28 (chromosome-wide P < 0.01) QTLs exhibited significant evidence of linkage, while the remaining 127 exhibited a suggestive effect on the above three traits at a chromosome-wide (P < 0.05) level. Multiple QTLs obtained from different families affect BW, TL, and BT and locate at close or identical positions. It suggests that same genetic factors may control variability in these traits. Furthermore, the results of the comparative QTL analysis of multiple families showed that one QTL was common in four of the eight families, nine QTLs were detected in three of the eight families, and 26 QTLs were found common to two of the eight families. These common QTLs are valuable candidates in marker-assisted selection.

CONCLUSION

A large number of QTLs were detected in the common carp genome and associated with growth-related traits. Some of the QTLs of different growth-related traits were identified at similar chromosomal regions, suggesting a role for pleiotropy and/or tight linkage and demonstrating a common genetic basis of growth trait variations. The results have set up an example for comparing QTLs in common carp and provided insights into variations in the identified QTLs affecting body growth. Discovery of these common QTLs between families and growth-related traits represents an important step towards understanding of quantitative genetic variation in common carp.

Molecular characterization and expression of three preprosomatostatin genes and their association with growth in common carp (Cyprinus carpio)

Somatostatins (SSs) are a structurally diverse family of peptides that play important roles in the regulation of growth, development and metabolism in vertebrates. In this study, three preprosomatostatin genes (PSSs) in the common carp, Cyprinus carpio (Cc) were identified and characterized. Based on cloned sequences and genome BLAST, six isoforms of the PSS gene in C. carpio (CcPSS) were identified and included CcPSS1a and CcPSS1b, CcPSS2a and CcPSS2b, and finally, CcPSS3a and CcPSS3b. The open reading frames (ORF) of CcPSS1a, CcPSS2a and CcPSS3a consist of 345, 336 and 363 nucleotides. During embryonic development, the expressions of CcPSS2 and CcPSS3 were first observed at the stage of optic vesicle, and CcPSS1 mRNA was initially detected at the stage of muscular effect. The highest mRNA levels of CcPSS1, CcPSS2 and CcPSS3 were observed at 1-day post-hatch (dph), 2-dph and the stage of heart beating, respectively. In the adult brain, the distributions of three CcPSS mRNAs were differential but overlapping in the hypothalamus, telencephalon and medulla oblongata. For peripheral tissues, all three CcPSS mRNAs were detected in the mid-intestine, and CcPSS1 and CcPSS3 mRNAs were also expressed in the liver. Owing to the importance of somatostatins on regulating growth, functional mutations of CcPSSs were identified in a C. carpio population. A total of 23 polymorphic sites were detected in CcPSS1a and CcPSS3a. Of them, two SNPs (CcPSS1a-g.922C>T, and CcPSS3a-g.1125C>A) were significantly associated with growth traits, indicating their potential applications in gene (marker)-assisted selective breeding in C. carpio.

Mapping QTLs for swimming ability related traits in Cyprinus carpio L

Body height (BH), head length (HL), snout length (SL), and tail length (TL) are important traits related with swimming ability of fish. Therefore, improving these traits will increase the production which is the basic goal of aquaculture breeding. To understand the genetic basis of swimming ability related traits in Cyprinus carpio L., a high-density linkage map spanning 3,301 cM in 50 linkage groups was utilized for quantitative trait locus (QTL) mapping. Mapping family comprised 190 offspring and 627 molecular markers were genotyped with average distance of 5.6 cM. A total of 15 QTLs including four (qBH13, qBH30, qBH33, qBH48) for BH, four (qHL10, qHL18, qHL29, qHL48) for HL, three (qSL24, qSL27, qSL45) for SL, and four (qTL15, qTL17, qTL18, qTL44) for TL were detected on 13 linkage groups LG10, LG13, LG15, LG17, LG18, LG24, LG27, LG29, LG30, LG33, LG44, LG45, and LG48. Each LG consisted on single QTL except LG18 and LG48. LG18 was found with two QTLs associated with HL and TL. While LG48 was comprised, the QTLs related with BH and HL. The phenotype variance was recorded from 12.6 to 40.6 %. Five QTLs, qHL48, qSL45, qTL15, qTL18, and qTL44, explained phenotype variance of >20 % with a significant levels of 0.047, 0.049, 0.037, 0.025, and 0.023, respectively. The neighbored loci of these QTLs were considered as main region of chromosomes controlling the traits. These identified genetic regions will be the main source of discovering gene(s) associated with swimming ability related traits in C. carpio L.

Microsatellite-centromere mapping in common carp through half-tetrad analysis in diploid meiogynogenetic families

Gene-centromere (G-C) mapping provides insights into the understanding of the composition, structure, and evolution of vertebrate genomes. Common carp (Cyprinus carpio) is an important aquaculture fish and has been proposed to undertake tetraploidization. In this study, we selected 214 informative microsatellite markers across 50 linkage groups of a common carp genetic map to perform gene-centromere mapping using half-tetrad analysis. A total of 199 microsatellites were segregated under the Mendelian expectations in at least one of the three gynogenetic families and were used for G-C distance estimation. The G-C recombination frequency (y) ranged from 0 to 0.99 (0.43 on average), corresponding to a fixation index (F) of 0.57 after one generation of gynogenesis. Large y values for some loci together with significant correlation between G-C distances and genetic linkage map distances suggested the presence of high interference in common carp. Under the assumption of complete interference, 50 centromeres were localized onto corresponding linkage groups (LGs) of common carp, with G-C distances of centromere-linked markers per LG ranging from 0 to 10.3 cM (2.9 cM on average). Based on the information for centromere positions, we proposed a chromosome formula of 2n = 100 = 58 m/sm + 42 t/st with 158 chromosome arms for common carp, which was similar to a study observed by cytogenetic method. The examination of crossover distributions along 10 LGs revealed that the proportion of crossover chromatids was overall higher than that of non-crossover chromatids in gynogenetic progenies, indicating high recombination levels across most LGs. Comparative genomics analyses suggested that the chromosomes of common carp have undergone extensive rearrangement after genome duplication. This study would be valuable to elucidate the mechanism of genome evolution and integrate physical and genetic maps in common carp.

Appearance traits in fish farming: progress from classical genetics to genomics, providing insight into current and potential genetic improvement

Appearance traits in fish, those external body characteristics that influence consumer acceptance at point of sale, have come to the forefront of commercial fish farming, as culture profitability is closely linked to management of these traits. Appearance traits comprise mainly body shape and skin pigmentation. Analysis of the genetic basis of these traits in different fish reveals significant genetic variation within populations, indicating potential for their genetic improvement. Work into ascertaining the minor or major genes underlying appearance traits for commercial fish is emerging, with substantial progress in model fish in terms of identifying genes that control body shape and skin colors. In this review, we describe research progress to date, especially with regard to commercial fish, and discuss genomic findings in model fish in order to better address the genetic basis of the traits. Given that appearance traits are important in commercial fish, the genomic information related to this issue promises to accelerate the selection process in coming years.

QTL mapping for economically important traits of common carp (Cyprinus carpio L.)

Quantitative trait loci (QTL) were analyzed for three economically important traits, i.e., body weight (BW), body length (BL), and body thickness (BT), in an F1 family of common carp holding the 190 progeny. A genetic linkage map spanning 3,301 cM in 50 linkage groups with 627 markers and an average distance of 5.6 cM was utilized for QTL mapping. Sixteen QTLs associated with all three growth-related traits were scattered across ten linkage groups, LG6, LG10, LG17, LG19, LG25, LG27, LG28, LG29, LG30, and LG39. Six QTLs for BW and five each for BL and BT explained phenotypic variance in the range 17.0-32.1%. All the nearest markers of QTLs were found to be significantly (p ≤ 0.05) related with the trait. Among these QTLs, a total of four, two (qBW30 and qBW39) related with BW, one (qBL39) associated with BL, and one (qBT29) related to BT, were found to be the major QTLs with a phenotypic variance of >20%. qBW30 and qBW39 with the nearest markers HLJ1691 and HLJ1843, respectively, show significant values of 0.0038 and 0.0031, correspondingly. QTLs qBL39 and qBT29 were found to have significant values of 0.0047 and 0.0015, respectively. Three QTLs (qBW27, qBW30, qBW39) of BW, two for BL (qBL19, qBL39), and two for BT (qBT6, qBT25) found in this study were similar to populations with different genetic backgrounds. In this study, the genomic region controlling economically important traits were located. These genomic regions will be the major sources for the discovery of important genes and pathways associated with growth-related traits in common carp.

Mapping quantitative trait loci (QTL) for body weight, length and condition factor traits in backcross (BC1) family of Common carp (Cyprinus carpio L.)

Body weight and length are economical important traits in aquaculture species influenced by quantitative trait loci (QTL) and environmental factors. In this study, a backcross (BC1) common carp family, with 86 progeny, was utilized to construct genetic map for preliminary QTL mapping. The genetic map was constructed with 366 markers, including 191 SNP from gene, coverage 50 linkage groups with an average marker distance of 18.5 cM. A total of fourteen QTLs associated with body weight (BW), body length (BL) and condition factor (K) were detected on ten linkage groups (LGs). Among these QTLs detected, three (qBW8, qBL8 and qK8) were associated with BW, BL and K respectively, were mapped on LG8. qBW8 and qK8 were identified on similar interval neared locus HLJ2394 explained 14.9 and 20.9 % of the phenotype variance, while qBL8 was identified on separate nearby locus HLJ571 with 30.8 % of phenotype variance. Two QTLs, qBW13 and qK13, related with BW and K separately, were found on LG13 at different locus with phenotype variance of 25.3 and 20.9 %. Other two QTLs, qBW19 and qBL19, associated to BW and BL were mapped on same region near SNP0626 on LG19, and explained 10.3 and 15.6 % of phenotype variance. While other seven QTLs related with BW and BL were located on different LGs. Confidential interval was ranged from 1.1 to 10 cM in the present study. These markers, with lower QTL interval, have great influence on the body weight and length. Therefore, these QTLs will be helpful to find out the genes related with specific trait.