Transcriptomic and metabonomic analyses reveal roles of VPS 29 in carotenoid accumulation in adductor muscles of QN Orange scallops

Integration of histopathology, transcriptomics and non-targeted metabolomics reveals toxic effects of thiamethoxam under acute stress in mirror carp (Cyprinus carpio var. Longke-11 mirror)

In recent years, the increasing application of thiamethoxam (THM), coupled with its high leaching and solubility in water, has led to growing concerns regarding THM residues in aquatic environments, which may pose toxic effects on aquatic organisms, particularly fish. However, the toxicological mechanisms of THM in freshwater fish remain unclear. In this study, using histopathology, transcriptomics, and non-targeted metabolomics, the toxic effects of different concentrations of THM under acute stress (96 h) were investigated in mirror carp (Cyprinus carpio var. Longke-11 mirror). The results showed that under acute THM stress, liver tissues of the mirror carp exhibited vacuolation, cellular degeneration, and enhanced cytoplasmic eosinophilia, while gill tissues displayed epithelial structure loss, epithelial cell detachment, degeneration, and vacuolation, with the severity of lesions increasing with exposure concentration. Transcriptomic analysis revealed that the number of differentially expressed genes (DEGs) increased with the concentration of THM. Genes related to immune response and antioxidant stress were mostly downregulated, while genes related to inflammation and apoptosis were predominantly upregulated. The downregulation of common DEGs (SLC7A11, ITLN, CDH17) further confirmed these results. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed significant enrichment in pathways related to inflammation and oxidative stress, with the NF-kappa B signaling pathway identified as the key pathway affected. Metabolomic analysis showed that differentially expressed metabolites (SCMs) associated with amino acid and lipid metabolism were significantly downregulated. The downregulation of SCM acetylcysteine further affected the antioxidant capacity of mirror carp. Moreover, different concentrations of THM affected phenylalanine metabolism, cysteine and methionine metabolism, and biosynthesis of unsaturated fatty acids in the liver of mirror carp. Integrated analysis of apoptosis-related factors (TP53INP1, PRF1, Sphingosine) upregulation and anti-apoptotic factors (Bcl2l1) downregulation suggested that THM induces apoptosis in mirror carp cells. These results indicate that THM stress affects the immune system, amino acid, and lipid metabolism in mirror carp, leading to inflammation, oxidative stress, and apoptosis. This study provides preliminary insights into the toxic mechanisms of THM in fish and can serve as a scientific basis for THM risk assessment and environmental protection.

The roles of a MiRNA and its targeted methyltransferase 3 in carotenoid accumulation in adductor muscles of QN orange scallops

BACKGROUND

QN Orange scallops are interspecific hybrids with orange adductor muscles that are rich in carotenoids. In this study, analysis of miRNA expression profiles was performed to explore possible regulatory patterns involved in carotenoid accumulation in adductor muscles of QN Orange scallops.

RESULTS

A total of 91 differentially expressed miRNA between the white and orange adductor muscles were identified. GO and KEGG analysis of target genes of differentially expressed miRNAs revealed enrichments in the transmembrane transporter activity-related pathways, kinase activity-related pathways, signal transduction-related pathways, ATP binding cassette transporters (ABC transporters), retinol metabolism, lipid-related metabolism, and calcium signaling pathway. In particular, miRNA Contig1462_36180, which was shown to negatively regulate the activity of methyltransferase 3 (METTL3) by dual-luciferase reporter assay, may play a pivotal role in the accumulation of carotenoids. Furthermore, METTL3 interference seemed to reduce the pectenoxanthin content and m6A level.

CONCLUSION

It is thus speculated that Contig1462_36180 may regulate m6A methylation by regulating METTL3, which in turn affects pectenoxanthin accumulation in QN Orange scallops.

Transcriptomic and Physiological Analysis Reveal Melanin Synthesis-Related Genes and Pathways in Pacific Oysters (Crassostrea gigas)

Shell color is one of the shell traits of molluscs, which has been regarded as an economic trait in some bivalves. Pacific oysters (Crassostrea gigas) are important aquaculture shellfish worldwide. In the past decade, several shell color strains of C. gigas were developed through selective breeding, which provides valuable materials for research on the inheritance pattern and regulation mechanisms of shell color. The inheritance patterns of different shell colors in C. gigas have been identified in certain research; however, the regulation mechanism of oyster pigmentation and shell color formation remains unclear. In this study, we performed transcriptomic and physiological analyses using black and white shell oysters to investigate the molecular mechanism of melanin synthesis in C. gigas. Several pigmentation-related pathways, such as cytochrome P450, melanogenesis, tyrosine metabolism, and the cAMP signaling pathway were found. The majority of differentially expressed genes and some signaling molecules from these pathways exhibited a higher level in the black shell oysters than in the white, especially after L-tyrosine feeding, suggesting that those differences may cause a variation of tyrosine metabolism and melanin synthesis. In addition, the in vitro assay using primary cells from mantle tissue showed that L-tyrosine incubation increased cAMP level, gene and protein expression, and melanin content. This study reveals the difference in tyrosine metabolism and melanin synthesis in black and white shell oysters and provides evidence for the potential regulatory mechanism of shell color in oysters.