Explore the vast range of titles available.

Angiotensin-I-converting enzyme (ACE) inhibitory peptides derived from natural products have shown a blood pressure lowering effect with no side effects. In this study, two novel ACE inhibitory peptides (His-Leu-His-Thr, HLHT and Gly-Trp-Ala, GWA) were purified from pearl oyster (Pinctada fucata martensii) meat protein hydrolysate with alkaline protease by ultrafiltration, polyethylene glycol methyl ether modified immobilized metal ion affinity medium, and reverse-phase high performance liquid chromatography. Both peptides exhibited high ACE inhibitory activity with IC50 values of 458.06 ± 3.24 μM and 109.25 ± 1.45 μM, respectively. Based on the results of a Lineweaver-Burk plot, HLHT and GWA were found to be non-competitive inhibitor and competitive inhibitor respectively, which were confirmed by molecular docking. Furthermore, the pearl oyster meat protein hydrolysate exhibited an effective antihypertensive effect on SD rats. These results conclude that pearl oyster meat protein is a potential resource of ACE inhibitory peptides and the purified peptides, HLHT and GWA, can be exploited as functional food ingredients against hypertension.

The Akoya pearl oyster ( Pinctada fucata (Gould)) is the most important species for pearl cultivation in Japan. Mass mortality of 0-year-old juvenile oysters and anomalies in adults, known as summer atrophy, have been observed in major pearl farming areas during the season when seawater temperatures exceed about 20 °C since 2019. In this study, we identified a novel birnavirus as the pathogen of summer atrophy and named it Pinctada birnavirus (PiBV). PiBV was first presumed to be the causative agent when it was detected specifically and frequently in the infected oysters in a comparative metatranscriptomics of experimentally infected and healthy pearl oysters. Subsequently, the symptoms of summer atrophy were reproduced by infection tests using purified PiBV. Infection of juvenile oysters with PiBV resulted in an increase in the PiBV genome followed by the atrophy of soft body and subsequent mortality. Immunostaining with a mouse antiserum against a recombinant PiBV protein showed that the virus antigen was localized mainly in the epithelial cells on the outer surface of the mantle. Although the phylogenetic analysis using maximum likelihood method placed PiBV at the root of the genus Entomobirnavirus, the identity of the bi-segmented, genomic RNA to that of known birnaviruses at the full-length amino acid level was low, suggesting that PiBV forms a new genus. The discovery of PiBV will be the basis for research to control this emerging disease.

Pinctada fucata martensii ( P. f. martensii ) is one of the main pearl oysters cultured in artificial seawater in China. However, it is highly susceptible to pathogen infection under intensive cultivation near the coast. MicroRNAs (miRNAs), as an innovative and potent regulator of immune function, play a pivotal role in the immune response of pearl oysters to external stimuli and are a potent marker for the response of P. f. martensii to infection. This study identified two novel miRNAs, novel-13 and novel-44 , from the whole transcriptome of the P. f. martensii hemocyte before and after infection with Vibrio parahaemolyticus . The dual luciferase results showed that novel-13 negatively regulated LAAO and novel-44 negatively regulated ILK . The activity of antioxidant-related enzymes increased significantly in the synthetic miRNA ( novel-13 and novel-44 ) inhibitors and decreased significantly in the synthetic miRNA mimics. In the challenge experiment, injection with miRNA inhibitor increased the relative survival percentage by 10% compared with the control group. In conclusion, the overexpression of novel-13 and novel-44 can decrease the activity of immune and antioxidant-related enzymes, possibly affecting immune regulation in P. f. martensii by negatively regulating the LAAO and ILK target genes.

Despite its economic importance, we have a limited understanding of the molecular mechanisms underlying shell formation in pearl oysters, wherein the calcium carbonate crystals, nacre and prism, are formed in a highly controlled manner. We constructed comprehensive expressed gene profiles in the shell-forming tissues of the pearl oyster Pinctada fucata and identified novel shell formation-related genes candidates. We employed the GS FLX 454 system and constructed transcriptome data sets from pallial mantle and pearl sac, which form the nacreous layer, and from the mantle edge, which forms the prismatic layer in P. fucata. We sequenced 260477 reads and obtained 29682 unique sequences. We also screened novel nacreous and prismatic gene candidates by a combined analysis of sequence and expression data sets, and identified various genes encoding lectin, protease, protease inhibitors, lysine-rich matrix protein, and secreting calcium-binding proteins. We also examined the expression of known nacreous and prismatic genes in our EST library and identified novel isoforms with tissue-specific expressions. We constructed EST data sets from the nacre- and prism-producing tissues in P. fucata and found 29682 unique sequences containing novel gene candidates for nacreous and prismatic layer formation. This is the first report of deep sequencing of ESTs in the shell-forming tissues of P. fucata and our data provide a powerful tool for a comprehensive understanding of the molecular mechanisms of molluscan biomineralization.

Among the anthropogenic stresses that marine ecosystems face, biological invasions are one of the major threats. Recently, as a result of increasingly intense anthropogenic disturbance, numerous marine species have been introduced to their non-native ranges. However, many introduced species have uncertain original sources. This prevents the design and establishment of methods for controlling or preventing these introduced species. In the present study, genomic sequencing and population genetic analysis were performed to detect the geographic origin of the introduced Pinctada fucata population in the Mischief Reef of the South China Sea. The results of population genetic structure analysis showed a close relationship between the Mischief Reef introduced population and the Lingshui population, indicating that Lingshui may be the potential geographical origin. Furthermore, lower heterozygosity and nucleotide diversity were observed in the introduced population in Mischief Reef, indicating lower genetic diversity than in other native populations. We also identified some selected genomic regions and genes of the introduced population, including genes related to temperature and salinity tolerance. These genes may play important roles in the adaptation of the introduced population. Our study will improve our understanding of the invasion history of the P. fucata population. Furthermore, the results of the present study will also facilitate further control and prevention of invasion in Mischief Reef, South China Sea.

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression via the recognition of their target messenger RNAs. MiR-10a-3p plays an important role in the process of ossification. In this study, we obtained the precursor sequence of miR-10a-3p in the pearl oyster Pinctada fucata martensii (Pm-miR-10a-3p) and verified its sequence by miR-RACE technology, and detected its expression level in the mantle tissues of the pearl oyster P. f. martensii. Pm-nAChRsα and Pm-NPY were identified as the potential target genes of Pm-miR-10a-3p. After the over-expression of Pm-miR-10a-3p, the target genes Pm-nAChRsα and Pm-NPY were downregulated, and the nacre microstructure became disordered. The Pm-miR-10a-3p mimic obviously inhibited the luciferase activity of the 3′ untranslated region of the Pm-NPY gene. When the interaction site was mutated, the inhibitory effect disappeared. Our results suggested that Pm-miR-10a-3p participates in nacre formation in P. f. martensii by targeting Pm-NPY. This study can expand our understanding of the mechanism of biomineralization in pearl oysters.

DNA methylation is a type of epigenetic modification that alters gene expression without changing the DNA sequence and mediates some cases of phenotypic plasticity. In this study, we identified six DNA methyltransferase (DNMT) genes and two methyl-CpG binding domain protein2 (MBD2) gene from Pinctada fucata martensii. We also analyzed the genome-wide DNA methylation levels of mantle edge (ME) and mantle central (MC) from P. f. martensii via methylated immunoprecipitation sequencing (MeDIP-Seq). Results revealed that both ME and MC had 122 million reads, and had 58,702 and 55,721 peaks, respectively. The obtained methylation patterns of gene elements and repeats showed that the methylation of the protein-coding genes, particularly intron and coding exons (CDSs), was more frequent than that of other genomic elements in the pearl oyster genome. We combined the methylation data with the RNA-seq data of the ME and MC of P. f. martensii and found that promoter, CDS, and intron methylation levels were positively correlated with gene expression levels except the highest gene expression level. We also identified 313 differential methylation genes (DMGs) and annotated 212 of them. These DMGs were significantly enriched in 30 pathways, such as amino acid and protein metabolism, energy metabolism, terpenoid synthesis, and immune-related pathways. This study comprehensively analyzed the methylomes of biomineralization-related tissues and helped enhance our understanding of the regulatory mechanism underlying shell formation.

Microplastics (MPs), particularly polyvinyl chloride microplastics (PVC MPs) have become a notable environmental pollutant that affect various marine organisms such as Pinctada fucata martensii . As filter feeders, these bivalves consume significant volumes of water containing MPs, leading to contact with and ingestion of MPs. Moreover, given the ecological and economic importance of P. f. martensii in artificial pearl production, investigating the effects of PVC MPs exposure is crucial. This study aimed to investigate the effects of PVC MPs exposure on nucleus retention, pearl formation, oxidative stress by examining superoxide dismutase (SOD) activity, catalase (CAT) activity, lipid peroxidation (LPO), and total antioxidant capacity (TAOC) of P. f. martensii , while also exploring transcriptomic changes at different concentrations and exposure time points, including a recovery period. The pearl oysters were exposed to PVC MPs at concentrations of 1-, 2.5-, and 5-mg PVC MPs/L for 10 d followed by 6 d of recovery. After 1-, 4-, 10-d of exposure, and additional 6 d of recovery, samples were taken and analyzed. Findings revealed that only prolonged exposure (10 d) to PVC MPs affected SOD activity, while CAT activity, LPO, and TAOC remained unaffected throughout the experiment. Notably, SOD activity was restored during the 6-d recovery phase. Transcriptome analysis highlighted significant gene alterations linked to various pathways, affecting cellular processes, environmental information processing, genetic information processing, metabolism, and organismal systems, with an increase in pathway-related genes during recovery, implying a potential role of PVC MPs as gene inhibitors. This study provided insights into the effects of PVC MPs on P. f. martensii , shedding light on pearl retention, oxidative systems, and molecular pathways influenced by PVC MPs. Additionally, it contributed novel information on potential MPs exposure biomarkers, particularly relevant to marine organisms like P. f. martensii .

Ammonium (NH4+) plays a crucial role in the reproductive processes of key biotic groups in aquatic ecosystems—bivalves. This study aims to elucidate the effects of three different ammonium ion concentrations on sperm vitality, swimming kinematics, and morphology of Mimachlamys nobilis, Pinctada fucata martensii, and Saccostrea mordax. The results indicate that the sperm vitality and motility rates of M.nobilis and S. mordax are inversely proportional to the ammonium concentration, especially in the treatment group with an ammonium concentration of 3 mmol/L, where the decrease in sperm vitality and motility is most significant. In contrast, the sperm of P. fucata martensii reacted differently to increasing ammonium concentrations. After the addition of 2 mmol/L of ammonium, the sperm vitality and motility of P. fucata martensii reached a peak, showing a significant stimulatory effect. Additionally, as the ammonium concentration increased, the curling of the sperm flagella in M.nobilis and S. mordax increased. However, sperm flagella curling in P. fucata martensii showed no change compared to the control group. This study provides insights into the effects of ammonium concentrations on the sperm vitality and motility of three marine bivalve species and highlights the importance of sperm flagella curling as a factor affecting sperm.

Recently, a new pearl oyster Pinctada fucata martensii strain has begun to be cultured as seafood. In the present study, the seasonal variation (February and June) in biochemical composition and flavor compounds in two P. f. martensii strains (strain for pearl production was abbreviated to PP, and seafood was abbreviated to PE) were detected to compare the nutritional and flavor differences between them, and to provide a reference for the seasonal preference of consumers for eating P. f. martensii. The ratio of soft tissues in PE-Feb was significantly higher than that in PP-Feb (p < 0.05). The contents of ash, crude protein, and crude lipid were higher in PP than those in PE in the same season, while significantly higher contents of glycogen in the PE strain were observed compared to the PP strain in the same season (p < 0.05). The major amino acids (such as Glu and Asp) and PUFA (such as DHA and EPA) were almost the same in two P. f. martensii strains in the same season, while the contents of these nutrients were significantly higher in February compared to June (p < 0.05). Taurine content in PE-Feb was the highest (19.58 mg/g wet weight), followed by PP-Jun, PP-Feb, and PE-Jun. The umami and sweet FAA contents of the same P. f. martensii strain in February were significantly higher than those in June (p < 0.05). The AMP content in PP-Jun was the highest (64.17 mg/100 g wet weight), followed by PP-Feb, PE-Jun, and PE-Feb. Succinic acid was the major organic acid, and its content in February was significantly higher than in June (p < 0.05). The betaine content in PP-Feb was the highest (23.02 mg/g of wet weight), followed by PE-Feb (20.43 mg/g of wet weight), PP-Jun (16.28 mg/g of wet weight), and PE-Jun (12.33 mg/g of wet weight), and significant differences were observed among these four groups (p < 0.05). In conclusion, the edible P. f. martensii strain harvest in February is rich in protein, glycogen, PUFA (DHA and EPA), taurine, succinic acid, and betaine, which could provide healthy nutrition and a good flavor for humans.