Fucata Martensii Research Articles

Molecular cloning, expression pattern of β-carotene 15,15-dioxygenase gene and association analysis with total carotenoid content in pearl oyster Pinctada fucata martensii.

β-carotene-15,15-dioxygenase is an enzyme involved in carotenoid metabolism to catalyze oxidative cleavage of β-carotene at its central double bond to two molecules of retinal in intestinal cells of vertebrate. In this study, we cloned and characterized β-carotene-15,15-dioxygenase in pearl oyster Pinctada fucata martensii (PmβCDOX). The full length of PmβCDOX gene was 1802 bp, including 1554 bp of the open reading frame (ORF) that encoded 517 amino acids, a 5'UTR of 134 bp and a 3' UTR of 114 bp. PmβCDOX was expressed at various tissues with highest level in hepatopancreas. Eighteen and fifteen single nucleotide polymorphisms (SNPs) were separately obtained in the exon and promoter of PmβCDOX. Eight SNPs (six SNPs in the exon and two SNPs in the promoter region) were significantly associated to total carotenoid content (TCC) (P < .05). The eight SNPs of significantly associated TCC were divided three haploblocks. Haplotypes CCTT had larger TCC than other haplotypes. The present results suggest that PmβCDOX is involved in carotenoid metabolism in pearl oyster. Our study will be helpful for development gene marker in selective breeding programs for TCC trait of the species.

Towards a better understanding of allograft-induced stress response in the pearl oyster Pinctada fucata martensii: Insights from iTRAQ-based comparative proteomic analysis

Implantation of a spherical nucleus into a recipient oyster is a critical step in artificial pearl production. The implanted nucleus is known to trigger cellular stress responses at several levels, yet the molecular mechanism underpinning physiological adaptation of the pearl oysters to nucleus implantation is still poorly understood. In this study, we took advantage of the iTRAQ-based proteomics and LC-MS/MS approach to look into allograft induced gene regulation at the protein expression level in the pearl oyster Pinctada fucata martensii, across a period of 30 days following nucleus implantation. A wide variety of proteins, including a group of immune-related proteins such as E3 ubiquitin-ligase and heat shock proteins, exhibited differential expression in response to the surgical operation. Further comparisons between different sampling points revealed that GO terms including “translation” and “oxidation-reduction process” and KEGG pathways including “glycolysis/gluconeogenesis” and “pyruvate metabolism” were significantly enriched at several time points, indicating the important roles of these molecular events in the stress response of pearl oysters to nucleus implantation. In addition, considerable discrepancy between protein expression level and gene transcript abundancy was identified, as only a few genes showed at least 2-fold expression changes at both proteomic and transcriptomic levels. The result implies that post-transcriptional gene regulation for the key proteins may represent an important aspect of allograft-induced stress response in the pearl oysters. Taken together, the data obtained would contribute to a deeper understanding of the molecular mechanisms enabling stress adaptation of the pearl oysters in response to nucleus implantation.

Transcriptome analysis of growth heterosis in pearl oyster Pinctada fucata martensii.

Heterosis improves growth and survival of shellfish species. Although breeders have widely exploited heterosis, its underlying molecular mechanisms remain unclear. In this study, a 2 × 2 complete diallel cross was facilitated between two full‐sib families to produce two inbred families (A and D) and their reciprocal hybrid families (B and C) of pearl oyster Pinctada fucata martensii. Growth traits of the four families were compared at the adult stages. Transcriptome analysis was conducted on the four families using an Illumina sequencing platform. The results revealed that the growth traits of the four families significantly varied (P < 0.05). The mid‐parent heterosis values of shell length, shell height, shell width, shell weight, and total weight were 12.9%, 14.9%, 18.2%, 17.2%, and 33.2%, respectively. The B‐ and C‐inbred (A and D) triads had 79 and 68 differentially expressed genes (DEGs), respectively, which were dominantly nonadditive, including overdominance, underdominance, and low‐parent dominance. Gene ontology term analysis showed that the DEGs in the B‐ and C‐inbred triads were enriched for metabolic process, cellular process cell part, binding, and catalytic activity. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis indicated that the DEGs in the B‐ and C‐inbred triads were involved in focal adhesion, the P13K‐Akt signaling pathway, the mRNA surveillance pathway, and the focal adhesion pathway. The reliability of the sequencing data was confirmed by real‐time polymerase chain reaction analysis of six growth‐related genes. The findings of this study provide new insights into heterosis for growth traits and the design of genetic breeding programs for this species.

Molecular and functional analysis of PmCHST1b in nacre formation of Pinctada fucata martensii.

Keratan sulfate possesses considerable amounts of negatively charged sulfonic acid groups and participates in biomineralization. In the present study, we investigated characteristics and functions of a CHST1 gene identified from the pearl oyster Pinctada fucata martensii (PmCHST1b) which participated in the synthesis of keratan sulfate. PmCHST1b amino acid sequence carried a typical sulfotransferase-3 domain (sulfotransfer-3 domain) and belonged to membrane-associated sulfotransferases. Homologous analysis of CHST1 from different species showed the conserved motif (5' PSB motif and 3' PB motif) which interacted with 3'-phosphoadenosine-5'-phosphosulfate (PAPS). Structure analysis of sulfotransferase domain indicted that PmCHST1b showed the conserved catalytic structure character and the relationships presented in the phylogenetic tree conformed to that of traditional taxonomy. Expression pattern of PmCHST1b in different tissues and development stages showed that PmCHST1b widely expressed in all the detected tissues and development stages and showed the highest expression level in the central zone of mantle (MC). PmCHST1b expressed highly in the trochophore, D-stage larvae and spat which corresponded to prodissoconch and dissoconch shell formation, respectively. RNA interference (RNAi) successfully inhibited expression level of PmCHST1b in MC (P<0.05), and sulfate polymer content in the extrapallial fluid significantly reduced (P<0.05). Crystallization of shell nacre became irregular. Results above indicated that PmCHST1b may affect nacre formation by participating in synthesis of keratan sulfate in extrapallial fluid. This study provided fundamental materials for further research on the role of sulfotransferases and keratan sulfate in nacre formation.

Molecular cloning and characteristics analysis of Pmtgfbr1 from Pinctada fucata martensii

Pinctada fucata martensii is cultured for pearl production. Growth improvement has received considerable research interest. Transforming growth factor β type Ⅰ receptor (TβR-I), which is involved in signals transmission of transforming growth factor beta (TGF-β), participates in cell proliferation and growth. In this study, we characterized a Tgfbr1 gene which encoded TβR-I from P. fucata martensii (Pmtgfbr1). Pmtgfbr1 cDNA contains an open reading frame of 1569 bp and encodes a polypeptide of 522 amino acids (aa). Pmtgfbr1 possesses a typical TβR-I structure (extracellular receptor ligand domain, transmembrane domain, and cytoplasmic tyrosine kinase catalytic domain). Pmtgfbr1 is expressed in all the studied tissues and exhibited the highest expression level in the adductor muscle. Moreover, Pmtgfbr1 exhibited the lower expression level in the larger group (L) than that in the smaller group (S) and is negatively correlated with growth traits (P < 0.01). Our results indicated that Pmtgfbr1 is a candidate functional gene associated with growth traits.

Adaptive response of pearl oyster Pinctada fucata martensii to low water temperature stress

The pearl oyster Pinctada fucata martensii is a warm-water shellfish that is sensitive to cold environments. To investigate its potential adaptation to low-temperature stress, the selected line (SL) and based population (BP) were sampled to undergo transcriptome sequence. Results of transcriptome analysis showed 572 significant differentially expressed genes. The typical HSP70 and HSP40 exhibited the polar expression model in the two groups. Meanwhile, the related genes that involved in energy release mediated by oxidative phosphorylation and the biosynthesis of unsaturated fatty acid were increased in the SL. The apparent enrichment of different expressed genes in amino acid metabolism indicated that the small molecule system with amino acids was one of the main regulator for low-temperature stress. The different expressions of immune-related and lysosome protein encoding genes also reflected the variation of immunity in the two groups and indicated that it could affect the adaptation ability in different temperature. In addition, the similar trends of different expression of typical genes between two groups were obtained by using RNA-seq and qRT-PCR. These results suggested that multi-system adjustments are involved in the processes of low water temperature stress in pearl oyster, providing insights into the response systems of shellfish to acclimatise with ambient environment change.

The effects of cryoprotectants on sperm motility of the Chinese pearl oyster, Pinctada fucata martensii

Cryopreservation has been widely employed to preserve genetic material of aquatic animals. Although of common use in bivalves, resulting effects due to the toxicity of the cryoprotectants dimethyl sulfoxide (DMSO), propanediol (PG), methanol (MET) and ethylene glycol (EG), upon sperm motility in the Chinese pearl oyster, Pinctada fucata martensii, has remained undocumented. This study endeavors to identify the least toxic among the effective cryoprotectant agents by observing and comparing their toxic effects on sperm motility under varying concentrations and duration of exposure. Sperm samples were exposed during controlled experiments, for 1, 3, 6, 9, 12 and 15 min durations, to each of the listed cryoprotectants at 5, 10, 15, and 20% (volume:volume) concentrations. Sperm motility was observed to diminish when exposed to all cryoprotectant solutions, and observations demonstrated that toxicity increased relative to both concentration and equilibration time. After 6 min of exposure to the cryoprotectants, sperm motility was seen to have diminished significantly in DMSO at just 5% concentration, and in MET, PG and EG at 10% concentrations, respectively (the values of the lowest observed effect concentrations). The relationship between the quantity of immotile sperm and the cryoprotectant concentration was described using the logarithmic regression equation. MET exhibited the lowest effective concentration required to inhibit sperm motility by 50% (EC50), followed by EG, PG and DMSO, in order. Therefore, MET proved most toxic under the test conditions for sperm of P. fucata martensii, whereas DMSO, PG and EG were observed as comparatively safer, suggesting that DMSO, PG and EG warrant further study in the application of cryopreservation of Chinese P. fucata martensii sperm.

Growth and survival of host pearl oyster Pinctada fucata martensii (Dunker, 1880) treated by different biofouling-clean methods in China

Pearl oyster Pinctada fucata martensii is an economically important species farmed to produce round nucleated pearl in China. However, pearl oyster shells are commonly exposed to biofouling, which is manually cleaned. This study experimentally evaluates the effects of biofouling cleaning by Siganus fuscescens (Houttuyn, 1782) foraging on growth performance and pearl traits of host pearl oyster P. fucata martensii. Three groups designated as EG1, EG2 and EG3 were set in the experiment. In EG1, biofouling was manually cleaned every 2 weeks and oysters were cultured in natural sea conditions. In EG2, biofouling was cleaned by foraging behavior of S. fuscescens every 2 weeks and oysters were cultured in natural sea conditions. In EG3, oysters were farmed in the net cage where S. fuscescens were stored. The survival rate of EG2 was higher than those of EG1 and EG3 and the daily growth rates of length and weight of shell and the thickness and weight of pearl of EG3 were significantly larger than those of EG1 and EG2. The survival rate, daily growth rates of the length and weight of shell, and thickness and weight of pearl were not significantly different between EG1 and EG2. This study suggested S. fuscescens foraging could evidently improve survival of host pearl oyster, which is promising to improve pearl yield in pearl oyster farms in China.

Deleterious Effects of Harmful Dinoflagellates and Raphidophytes on Egg Viability and Spermatozoa Swimming Velocity in the Japanese Pearl OysterPinctada fucata martensii

Several species of harmful algal blooms (HAB) exert inimical effects on bivalve molluscs, with mass mortalities and pathologies reported worldwide. Information on the effects of HAB on the reproduction of bivalve molluscs, however, remains very limited. The Japanese pearl oyster Pinctada fucata martensii is an important economic species cultured in Japan. In previous studies, harmful dinoflagellates and raphidophytes were shown to affect embryos and larvae of Japanese pearl oyster. In the present study, quantitative deleterious effects of Alexandrium catenella, Alexandrium affine, Heterosigma akashiwo, and Chattonella marina on egg viability and spermatozoa swimming velocity are reported. All four HAB species significantly reduced the swimming velocity of spermatozoa. Egg viability was affected only after exposure to A. catenella and A. affine. An additional cytotoxicity test using Vero cells showed that bioactive exudates are associated with the deleterious effects and these effects are more prominent during the death phase of the algal culture. The results of the present study warrant further research on the effects of HAB species on gamete quality of bivalves, further characterization of bioactive compounds secreted by Alexadnrium spp., and highlight the role of physical activation of the toxic mechanism of harmful raphidophytes suggested in a previous study and confirmed in the present study.

Association between Five Expressed Sequence Tag–Simple Sequence Repeat Markers and Four Growth Traits in Pinctada fucata martensii

AbstractThis study aimed to investigate the correlation between marker polymorphism and growth traits in Pinctada fucata martensii. Five microsatellite markers (2PM206, 3PM10, 4PM34, 4PM50, and PM6) derived from expressed sequence tags were selected and were applied in a total of 339 pearl oysters. Observed heterozygosity and expected heterozygosity of the five microsatellite loci ranged from 0.360 to 0.681 and 0.429 to 0.672, respectively. Four loci (2PM206, 4PM34, 4PM50, and PM6) deviated from Hardy–Weinberg equilibrium (P &gt; 0.05). Four growth traits, including shell height (SH), shell length (SL), shell width, and total weight (TW) were measured in all 339 samples. After Bonferroni correction, markers 2PM206, 4PM34, and 4PM50 were correlated with all four growth traits. Marker PM6 was significantly correlated with SH, SL, and TW, and marker 3PM10 was associated with SH and SL traits (P &lt; 0.05). These results provide useful information for marker‐assisted breeding programs in P. fucata martensii.

A novel toll-like receptor from the pearl oyster Pinctada fucata martensii is induced in response to stress.

Graft rejection due to immune incompatibility is a common occurrence in pearl culture, which often cause death to the host oyster. To improve cultured pearl production, host mortality and bead rejection rates must be reduced. Toll-like receptor 4 (TLR4) plays an important role in innate immunity, and may be related to allograft rejection. Here, we cloned the TLR4 cDNA from the pearl oyster Pinctada fucata martensii (PmTLR4). PmTLR4 cDNA was 3138bp, including a 2625bp open reading frame encoding 874 amino acids. The predicted PmTLR4 protein was structurally typical of the TLR family. PmTLR4 had relatively high sequence similarity and identity to the TLR4 of the Cyclina sinensis (48.1% and 27.6%, respectively). Multiple alignment of TLR4 sequences across species indicated that the Toll/interleukin-1 (IL-1) receptor domain was conserved among species. PmTLR4 mRNA was expressed in all tissues tested, with the most abundant mRNA expression in hepatopancreas and gill in P. fucata martensii. After being stressed by either lipopolysaccharide (LPS) exposure or the nucleus insertion operation, PmTLR4 mRNA expression increased significantly in the hemocytes as compared to controls. Peak level of PmTLR4 mRNA was observed 6h after the LPS injection, and 2d after the nucleus insertion operation. These data suggest that PmTLR4 may play a vital role in the induction of innate immunity and is therefore associated with allograft immunity in the pearl oyster P. fucata martensii.

The pearl oyster Pinctada fucata martensii genome and multi-omic analyses provide insights into biomineralization.

Nacre, the iridescent material found in pearls and shells of molluscs, is formed through an extraordinary process of matrix-assisted biomineralization. Despite recent advances, many aspects of the biomineralization process and its evolutionary origin remain unknown. The pearl oyster Pinctada fucata martensii is a well-known master of biomineralization, but the molecular mechanisms that underlie its production of shells and pearls are not fully understood. We sequenced the highly polymorphic genome of the pearl oyster and conducted multi-omic and biochemical studies to probe nacre formation. We identified a large set of novel proteins participating in matrix-framework formation, many in expanded families, including components similar to that found in vertebrate bones such as collagen-related VWA-containing proteins, chondroitin sulfotransferases, and regulatory elements. Considering that there are only collagen-based matrices in vertebrate bones and chitin-based matrices in most invertebrate skeletons, the presence of both chitin and elements of collagen-based matrices in nacre suggests that elements of chitin- and collagen-based matrices have deep roots and might be part of an ancient biomineralizing matrix. Our results expand the current shell matrix-framework model and provide new insights into the evolution of diverse biomineralization systems.

Effects of replacing microalgae with an artificial diet on pearl production traits and mineralization-related gene expression in pearl oyster Pinctada fucata martensii

The effects of replacing dietary microalgae with artificial diet on pearl production traits and biomineralization-related gene expression were investigated in pearl oyster (Pinctada fucata martensii). Three experiment groups (EG1, EG2 and EG3) were set. EG1 and EG3 were separately fed Platymonas subcordiformis and artificial diet (D4), respectively, and EG2 was fed with mixed P. subcordiformis and D4. A control group (CG) was cultured in natural sea. All groups were continuously fed for 150 days. The results showed that the survival rates of EG1, EG2 and EG3 were significantly higher than that of CG. No significant differences in retention rate and pearl thickness were observed among the four groups, but CG had the lowest values of both parameters. The relative expression levels of EGFR and FGF18 mRNA did not significantly differ among EG1, EG2 and EG3. Moreover, the relative expression levels of GHITM and TβR I mRNA significantly varied among the groups and EG3, and EG1 had the highest and lowest relative expression levels of GHITM and TβR I mRNA respectively. The relative expression levels of nacrein and chitin-binding mRNA significantly differed among the groups, and EG1 had the lowest expression levels of nacrein and chitin-binding mRNA. No significant differences in the relative expression levels of MSI60 and TIMP mRNA were observed among the groups. The results suggested that D4 can replace part of microalgae, which is helpful for further studies on developing artificial diet of pearl oyster.

Structure-based function prediction of the expanding mollusk tyrosinase family

Tyrosinase (Ty) is a common enzyme found in many different animal groups. In our previous study, genome sequencing revealed that the Ty family is expanded in the Pacific oyster (Crassostrea gigas). Here, we examine the larger number of Ty family members in the Pacific oyster by high-level structure prediction to obtain more information about their function and evolution, especially the unknown role in biomineralization. We verified 12 Ty gene sequences from Crassostrea gigas genome and Pinctada fucata martensii transcriptome. By using phylogenetic analysis of these Tys with functionally known Tys from other molluscan species, eight subgroups were identified (CgTy_s1, CgTy_s2, MolTy_s1, MolTy-s2, MolTy-s3, PinTy-s1, PinTy-s2 and PviTy). Structural data and surface pockets of the dinuclear copper center in the eight subgroups of molluscan Ty were obtained using the latest versions of prediction online servers. Structural comparison with other Ty proteins from the protein databank revealed functionally important residues (HA1, HA2, HA3, HB1, HB2, HB3, Z1–Z9) and their location within these protein structures. The structural and chemical features of these pockets which may related to the substrate binding showed considerable variability among mollusks, which undoubtedly defines Ty substrate binding. Finally, we discuss the potential driving forces of Ty family evolution in mollusks. Based on these observations, we conclude that the Ty family has rapidly evolved as a consequence of substrate adaptation in mollusks.

Effects of replacement of dietary microalgae with microencapsulated diet on pearl production traits, gene expression related to growth and mineralization in pearl oyster Pinctada fucata martensii

PDF HTML阅读 XML下载 导出引用 引用提醒 微胶囊饲料对马氏珠母贝育珠性能、生长基因和矿化基因表达的影响 DOI: 作者: 作者单位: 1. 广东海洋大学 水产学院, 广东 湛江 524088;2. 广东省珍珠养殖与加工工程技术研究中心, 广东 湛江 524088 作者简介: 王庆恒,副教授.E-mail:wangqingheng@163.com 通讯作者: 中图分类号: S963 基金项目: 广东省科技计划项目（2014A020208122）；国家贝类产业体系专项（CRAS-048）；广东省海洋渔业科技与产业发展专项（Z2014009；A201308A06） Effects of replacement of dietary microalgae with microencapsulated diet on pearl production traits, gene expression related to growth and mineralization in pearl oyster Pinctada fucata martensii Author: Affiliation: 1. Fisheries College, Guangdong Ocean University, Zhanjiang 524088, China;2. Pearl Breeding and Processing Engineering Technology Research Center of Guangdong Province, Zhanjiang 524088, China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:本研究分析了自主研发的微胶囊饲料替代微藻对马氏珠母贝（）育珠性能、生长相关基因和矿化相关基因表达的影响。共设置了3个实验组，其中，EG1组投喂亚心形扁藻（），EG2组投喂微胶囊饲料+亚心形扁藻，EG3组投喂微胶囊饲料。养殖170 d后，比较马氏珠母贝的育珠性能、闭壳肌生长相关基因、>0.05），所采收珍珠的珍珠层厚度及平均质量也不存在显著性差异（TβR I的相对表达量不存在显著性差异（>0.05），EG2和EG3组在EG3组中的表达量显著性高于EG1和EG2组（的相对表达量差异不显著（<0.05）。研究结果说明，该微胶囊饲料可以替代部分微藻进行育珠生产，为进一步研发马氏珠母贝的人工配合饲料及开展工厂化育珠积累了参考资料。 Abstract:The effects of replacement of a dietary microalgae with a microencapsulated diet on gene expressionrelated to pearl production traits, growth and biomineralization were studied in the pearl oyster . Three experimental groups were set up: EG1 was fed the marine green alga ; EG2 was fed a mixed diet of the microcapsules and the algae; and EG3 was fed only the microcapsules. The expression level of the growth-related genes in the adductor muscle (A), and the biomineralization-related genes in the mantle central (MC) and mantle edge (ME), were detected and compared among the three treatments after a 170-day indoor farming period. The results showed that survival rate, retention rate, the pearl nacre thickness, and average mass of the harvested pearls did not significantly differ (EGFR, I in the A did not significantly differ among the three treatments (N19 in the MC did not significantly differ among the three treatments ( was higher in EG2 and EG3 than in EG1, and the expression level of <0.05). No significant differences were detected in the relative expression levels of in the ME among the three treatments ( was higher in EG2 and EG3 than in EG1 (<0.05). These results suggest that the microencapsulated diet can replace part of the microalgae diet, which may be helpfully applied in future studies of artificial feed development for pearl oyster . 参考文献 相似文献 引证文献

Development of SSR marker by RNA-seq and its application in genotyping pearl sac in pearl oyster Pinctada fucata martensii

Background: Pearl oyster Pinctada fucata martensii is cultured for producing round nucleated pearls. Pearl production involves a surgical operation, where a mantle tissue graft from a donor oyster and a round nucleus are implanted in the gonad of a host oyster. Whether the mantle graft implanted in the gonad of a host oyster contribute to the formation of a pearl sac that secretes pearl nacre to form pearl should be determined. In April 2012, two full-sib families were used separately for donor and host oysters for a nucleus insertion operation. The pearl sac was sampled from the host oysters at day 60 after nucleus operation. A large number of simple sequence repeat (SSR) markers were developed by using Illumina HiSeq TM 2000 platform. The two full-sib families were also used to mine diagnostic SSR markers for genotyping donor oyster, host oyster and pearl sac. Results: A total of 3,168 microsatellite loci were identified in 39,078unigenes, and 1,977 SSR primers were designed by Primer 3.0. Forty-seven SSR primers were validated, and the rate of successful amplification was 72.3%. Two diagnostic SSR primers could successfully genotyped pearl sac, donor oyster and host oyster. Donor and host oysters were both homogenous and the alleles in pearl sac were identical to those in donor and host oysters. Conclusions: The present results confirmed that the mantle graft implanted in the gonad of host oyster contributed to the formation of the pearl sac in pearl oyster P . fucata martensii . Normal 0 21 false false false EN-US ZH-CN X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabla normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Times New Roman,serif; mso-ansi-language:EN-US; mso-fareast-language:ZH-CN;}

Association between novel EST-SNPs and commercial traits in Pinctada fucata martensii

To facilitate marker-assisted selection for genetic improvement of the pearl oyster Pinctada fucata martensii, two novel single nucleotide polymorphism (SNP) markers (A376C and A316C) were screened from two shell matrix genes (prismalin-14 and N19 gene), and genotyped to investigate their correlations to five commercial traits, including shell width (SW), shell length (SL), shell height (SH), hinge length (HL) and total weight (TW) in 160 pearl oysters. Both of the two loci showed AC heterozygous. The highest trait values of the five commercial traits measured were the CC genotype in the A316C SNP locus and the AC genotype in the A376C SNP locus, respectively. Significant differences in the trait values were detected between AA- and AC-type individuals (P=0.005 for SW, P=0.037 for SH, P=0.031 for HL and P=0.007 for TW), but not for SL (P=0.057) in the A376C locus. These results indicated that AC-type at locus A376C from prismalin-14 gene could be used as a preferred genotype for future selection in breeding program of pearl oyster.

Evaluation of genetic characteristics of wild and cultured populations of the Japanese pearl oyster Pinctada fucata martensii by using AFLP markers

Genetic characteristics of four wild (Mie, Fukui, Shimane and Nagasaki) and five cultured populations (selectively bred for 12 years with an origin of Ehime population) of the Japanese pearl oyster, Pinctada fucata martensii, were evaluated by using AFLP markers. Six primer pairs generated 1019 loci in total, among which 45.2–55.1 % was polymorphic among populations. Although there was no significant difference in gene diversity between wild (0.170–0.174) and cultured (0.158–0.173) populations, genetic relatedness in cultured populations (0.316–0.450) was about three times higher than that in wild populations (0.110–0.165). In addition, genetic differentiation was about twenty times larger in cultured populations (Nei’s distance: 0.0111) than in wild populations (Nei’s distance: 0.0005). These results mean that selective breeding can cause marked inbreeding as well as large genetic differentiation among cultured populations in a short period. On the other hand, it was suggested that genetic homogenization in the wild, probably due to a large-scale transport of cultured oysters, had progressed in the sea around Japan. In conclusion, it is necessary to prevent inbreeding by the reconsideration of the style of selective breeding in cultured populations, while the escape of gametes or spats of cultured strains in the wild should be avoided for the preservation of genetic characteristics in native populations of P. f. martensii.

Expression profiles of nine biomineralization genes and their relationship with pearl nacre thickness in the pearl oyster,Pinctada fucata martensiiDunker

Pinctada fucata martensii is an ideal animal for study of biomineralization. Although dozens of genes have been identified, the molecular mechanism of biomineralization remains still unclear. The purpose here was to discover the expression profiles of nine biomineralization genes in related tissues: mantle edge (ME), mantle centre (MC) and pearl sac (PS), and to explore the relationships between expression level and nacre thickness. The expression levels of seven genes (ACCBP, aspein, CaM, EFCBP, KRMP, nacrein and prismalin-14) showed no significant difference between ME and MC, but were significantly higher than those in PS. The expression level of N19 was the same in ME and PS, significantly higher than that in MC. However, msi60 in ME, MC and PS showed no significant differences in expression level. In addition, the correlations of expression levels between ME, MC and PS were highly significant, indicating that there are some similar function and mechanism among the three tissues. Also the nine genes had significant correlation of expression levels between one another. Furthermore, no other genes from oysters which produced pearls of different grades showed significant difference in the expression level, except CaM in MC, which had significantly higher expression level in the medium pearl grade than in the plain nucleus grade. Moreover, the expression level of msi60 in MC of host oyster was significantly correlated with produced pearl layer thickness, suggesting that msi60 might play an important role in pearl formation and host oyster may also participate in the development of pearl.

The Influence of Saibo Donor and Host on the Nacre Deposits of Pearls Produced fromPinctada Fucata Martensii

The pearl oyster Pinctada fucata martensii is the dominant species for production of marine pearls in China. To explore the relative contributions of donor and host oysters to nacre deposition in cultured pearls, donors of 3 size groups—large, medium, and small—and hosts of different sizes were used for pearl production. Resulting pearls were numbered to allow tracing of donor and host. Results showed that pearls developed from the 3 different groups of donors showed no significant difference in diameter, weight, and nacre thickness; however pearls cultured in different-size hosts differed significantly with regard to these parameters. Specifically, pearl size, weight, and nacre thickness correlated positively with the size and weight of host oysters, with coefficients ranging from 0.22–0.34. It is suggested that in selection of host oysters used for pearl production, if other conditions are equal, those of larger size and weight are more preferable, for they will presumably produce pearls of larger size and nacre thickness.