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Hedgehog signaling pathway participates in a chain of necessary physiological activities and dysregulation of the hedgehog signaling has been implicated in birth defects and diseases. Although substantial studies have uncovered that the hedgehog pathway is both sufficient and necessary for patterning vertebrate muscle differentiation, limited knowledge is available about its role in molluscan myogenesis. Here, the present study firstly identified and characterized the key genes (CgHh, CgPtc, CgSmo, CgGli) in the hedgehog pathway of the Pacific oyster Crassostrea gigas , and investigated the function of this pathway in embryonic myogenesis of C. gigas. Bioinformatics analysis revealed that the functional domains of the key genes were highly conserved among species. Quantitative analysis indicated that CgHh, CgPtc, CgGli mRNA began to accumulate during the blastula to gastrulation stages and accumulated throughout trochophore and into the D-shaped stage. RNA localization patterns by whole-mount in situ hybridization revealed that the key genes own the strongest specific staining in gastrulation, trochophore, and D-shaped stage. Hedgehog pathway genes showed a high expression level in myogenesis stage including trochophore and D-shaped stages, suggesting that the hedgehog pathway would be involved in myogenesis of C. gigas. In adult oysters, the key genes were expressed at various tissues, indicating that hedgehog pathway governed a series of development events. To further examine the role of hedgehog signaling in C. gigas myogenesis, we used cyclopamine treatment in C. gigas larvae to inhibit the signaling pathway. The quantification of the expression of the key genes in hedgehog pathway showed that expressions of key genes were severely down-regulated in treated larvae compared with normal larvae. The velum retractors, ventral retractors, anterior adductor, and posterior adductor muscles of larvae treated with cyclopamine at 4–6 μM for 6–12 h were severely destroyed, suggesting that the hedgehog pathway took part in the myogenesis of C. gigas. These findings provide a foundation for uncovering the molecular mechanisms of hedgehog signaling in molluscan physiological activity and enable us to better understand the signaling pathway involving in molluscan physiological activity. [ABSTRACT FROM AUTHOR]

Pacific oyster is one of the leading species in world aquaculture, but heritability estimation applying mixed-family approach has not been actively pursued. In this study, heritability for growth-related traits in the Pacific oyster was first estimated by creating a single cohort of 45 families in a full-factorial mating design consisting of nine sires and five dams. A total of 270 offspring were analysed and parentage assignment inferred by six microsatellite markers achieved 100% success. All parents contributed to the spawn and a total of 42 full-sib families were represented. Using an animal model, heritability estimates at 12 months of age were 0.49 ± 0.25 for shell height, 0.36 ± 0.19 for shell length, 0.45 ± 0.23 for shell width and 0.35 ± 0.17 for wet weight. Genetic correlation between shell height and wet weight was quite high (0.79 ± 0.25), suggesting that direct selection of shell height, which is an easily measurable trait, also improves wet weight. The results obtained in this study indicate that growth-related traits could be improved by exploiting additive genetic effects through selective breeding. [ABSTRACT FROM AUTHOR]

Shell coloration in many molluscs is highly variable. A shell color segregation study with progenies from a full factorial cross generated among Pacific oysters exhibiting distinct shell colors (golden, white and black) was conducted to investigate the inheritance of the golden shell color and its correlation with dark pigmentation. Random samples from twenty-three full-sib families were obtained and the shell coloration of offspring within each family was recorded. Results revealed that golden coloration was inherited in a different pattern from dark pigmentation, indicating its different genetic basis. Dark pigmentation was identified as a foreground color while golden or white color were background ones. The locus controlling background colors has two alleles with the allele for golden background being dominant to the allele for white background. In addition, the overlying foreground pigmentation of shells with a golden background was significantly lighter than that of shells with a white background, which suggested an epistatic effect of background color on shell foreground pigmentation. All these findings will facilitate the selection of elite oyster lines with desired shell coloration for aquaculture. [ABSTRACT FROM AUTHOR]

The Pacific oyster ( Crassostrea gigas ) is one of the most important farmed oysters worldwide. To improve breeding progress, research was done to identify molecular markers linked to shell pigmentation, which has been viewed as a key factor for product value. An F 1 -segregating population exhibiting a bimodal distribution of shell pigmentation intensity was obtained by crossing two wild oysters with opposite shell pigmentation. Genomic DNA from nine individuals with lightest shell pigmentation and nine individuals with darkest shell pigmentation were equally pooled for amplified fragment length polymorphism (AFLP) screening. In bulked segregant analysis, six out of 225 selective primer pair combinations produced seven polymorphic fragments tightly associated with shell pigmentation across the segregating population. The seven AFLP markers were mapped onto a single linkage group, and 80% of phenotypic variance could be explained by this locus. In conversion of the seven fragments into sequence-characterized amplified region (SCAR) markers, only one was successfully converted into a co-dominant SCAR marker, named SP-170. The SCAR marker was integrated into a previously constructed linkage map. The SCAR marker obtained in this study will be useful for marker-assisted selection of the Pacific oyster. [ABSTRACT FROM AUTHOR]

Paramyosin is a key component of thick filaments in invertebrate muscles. In this study, we isolated the full length cDNA of paramyosin from Pacific oyster (Crassostrea gigas) , and determined its pattern of expression during myogenesis. The full length paramyosin (CgPM) cDNA contains an open reading frame (ORF) of 2586 bp encoding a 861-amino acid protein. Sequence analysis revealed an assembly competence domain (ACD) and a heptad repeat (d-e-f-g-a-b-c) with 28-residue repeat zones in the CgPM primary structure, a characteristic of coiled-coil protein. Quantitative analysis of CgPM expression revealed a sharp increase in trochophore stage, and peaked at the D-shaped stage. Strong CgPM expression was found in smooth adductor muscle, followed by striated adductor muscle and mantle tissue. Whole-mount in situ hybridization (WISH) showed a restricted pattern of CgPM expression in adductor muscle, larval velum retractor and foot muscles at the umbo and eyed larval stages. These data indicate that CgPM is strongly expressed during larval myogenesis in C. gigas , which provides the basis for further functional studies of paramyosin in oyster to better understand the molecular and cellular mechanisms of muscle formation in mollusks. [Display omitted] • Here, the sequence characteristics and expression profiles of paramyosin in Crassostrea gigas (CgPM) were investigated. The main results are as follows: • Sequence analysis of CgPM revealed an assembly competence domain (ACD) and a heptad repeat (d-e-f-g-a-b-c) with 28-residue repeat zones in the CgPM primary structure, a characteristic of coiled-coil protein. • Quantitative analysis of CgPM expression revealed a sharp increase in trochophore stage, and peaked at the D-shaped stage. • Strong CgPM expression was found in smooth adductor muscle, followed by striated adductor muscle and mantle tissue. • Whole-mount in situ hybridization (WISH) showed a restricted pattern of CgPM expression in adductor muscle, larval velum retractor and foot muscles at the umbo and eyed larval stages. [ABSTRACT FROM AUTHOR]

The Pacific oyster (Crassostrea gigas) is one of the most important species which has the largest production among all cultured shellfish. Recently, several shell color strains of C. gigas have been developed to improve the commercial values, however the inheritance of shell pigmentation is still unclear. A total of 29 families cross-mated between different pigmented oysters were produced to investigate the inheritance of the shell pigmentation and purple pigmentation. Random samples from each family were obtained and their shell pigmentation were recorded. Results revealed that shell pigmentation was controlled by two genetic locus, among which one is responsible for secretion of pigmentation and the other is responsible for distribution mode of pigmentation. The locus controlling the secretion of pigmentation has two alleles with the allele for the presence of pigmentation being dominant to the allele for the absence of pigmentation. Similarly, another locus controlling the distribution mode of pigmentation has two alleles with the allele for striped distribution being dominant to the allele for solid distribution. In addition, one independent locus with two alleles was suggested to control the purple-striped pigmentation, which one allele for shell devoid of purple pigmentation is dominant to another allele for shell with purple pigmentation. The findings will provide valuable information for the efficient selective breeding of shell color strains in the Pacific oyster. • A two-locus model for inheritance of shell pigmentation were demonstrated. • The allele for secretion of pigmentation is dominant to the other allele for absence of pigmentation. • The allele for striped distribution of pigmentation is dominant to the allele for solid distribution of pigmentation. • An indenpendent loci was found to control the inheritance of purple striped pigmentation. [ABSTRACT FROM AUTHOR]

The pacific oyster ( Crassostrea gigas ) is one of the most widely farmed aquatic animal species and of great economic importance. Mantle edge color in C . gigas is highly variable and considered as a new potential trait for a better commercial value. In this study, heritability for mantle edge pigmentation and its correlation with shell pigmentation were explored in the white-shell strain of C . gigas with mixed-family method. A total of 460 offspring raised under communal conditions were successfully assigned to their parents using four multiplex PCR protocols based on 11 microsatellite loci. Mantle edge pigmentation was measured through assay of melanin content using spectrophotometric analysis. Animal model heritability estimate were 0.215 ± 0.092 for mantle edge pigmentation. The genetic and phenotypic correlations between two pigment traits were 0.980 ± 0.094 and 0.423 ± 0.042, respectively. Pearson analyses for average mantle edge and shell pigmentation of family also showed strong and significant correlation ( r = 0.729, P = 0.000, n = 29). Chi-square analyses showed that mantle edge pigmentation of family 7 segregated into “lighter” and “darker” groups in a 3:1 ratio ( P = 0.833), suggesting that a major locus might control mantle edge pigment trait. The results obtained in this study will benefit selective breeding of C . gigas with desired mantle and shell pigmentation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Triploids represent advantages to oyster industry. [•] We develop a molecular tool using genomic resources for triploid identification. [•] Eight of highly polymorphic and centromere-distant microsatellites were used. [•] This molecular tool was cost-effective, versatile and accurate for triploidy detection. [ABSTRACT FROM AUTHOR]