In the cultivation of Mytilus unguiculatus, the broodstock are shade-dried to stimulate sperm and egg production. To identify the functional genes affecting gonad development in M. unguiculatus, the transcriptome of gonads in mussels stimulated by shade-drying and those not stimulated were compared. Differential gene expression analysis revealed that there were 22 differentially expressed genes (DEGs) in the testis and 70 DEGs in the ovary among the experimental groups. KEGG enrichment analysis identified a total of 11 pathways that might be related to environmental stimuli affecting gonadal development. Nicotinic acetylcholine receptors (AChRs), the cholecystokinin A receptor (CCKAR), hypocretin (orexin) receptor 2 (HCRTR2), and gamma-aminobutyric acid type B receptor (GABBR) were highly expressed in the neuroactive ligand-receptor interaction pathway, indicating that these genes might be involved in the transduction of environmental information that stimulates gonadal development. Meanwhile, nuclear receptor co-repressor 2 (NCoR2) was highly expressed in the notch signaling pathway, indicating that NCoR2 might be involved in the regulation of gonad development. To validate the transcriptome data, we selected five DEGs in the KEGG signaling pathway, including AChRs, CCKAR, HCRTR2, GABAB, and NCoR2, for real-time quantitative PCR (RT-qPCR), which produced results consistent with the RNA-Seq data. The transcriptome analysis and gene pathway identification in this study have enhanced our comprehension of the reproductive mechanisms in M. unguiculatus.

Interleukin-17 (IL-17) represents a class of proinflammatory cytokines involved in chronic inflammatory and degenerative disorders. Prior to this study, it was predicted that an IL-17 homolog could be targeted by Mc-novel_miR_145 to participate in the immune response of Mytilus coruscus. This study employed a variety of molecular and cell biology research methods to explore the association between Mc-novel_miR_145 and IL-17 homolog and their immunomodulatory effects. The bioinformatics prediction confirmed the affiliation of the IL-17 homolog with the mussel IL-17 family, followed by quantitative real-time PCR assays (qPCR) to demonstrate that McIL-17-3 was highly expressed in immune-associated tissues and responded to bacterial challenges. Results from luciferase reporter assays confirmed the potential of McIL-17-3 to activate downstream NF-κb and its targeting by Mc-novel_miR_145 in HEK293 cells. The study also produced McIL-17-3 antiserum and found that Mc-novel_miR_145 negatively regulates McIL-17-3 via western blotting and qPCR assays. Furthermore, flow cytometry analysis indicated that Mc-novel_miR_145 negatively regulated McIL-17-3 to alleviate LPS-induced apoptosis. Collectively, the current results showed that McIL-17-3 played an important role in molluscan immune defense against bacterial attack. Furthermore, McIL-17-3 was negatively regulated by Mc-novel_miR_145 to participate in LPS-induced apoptosis. Our findings provide new insights into noncoding RNA regulation in invertebrate models.

Growth is a fundamental aspect of aquaculture breeding programs, pivotal for successful cultivation. Understanding the mechanisms that govern growth and development differences across various stages can significantly boost seedling production of economically valuable species, thereby enhancing aquaculture efficiency and advancing the aquaculture industry. Mytilus coruscus, a commercially vital marine bivalve, underscores this importance. To decipher the intricate molecular mechanisms dictating growth and developmental disparities in marine shellfish, we conducted transcriptome sequencing and meticulously analyzed gene expression variations and molecular pathways linked to growth traits in M. coruscus. This study delved into the molecular and gene expression variations across five larval development stages, with a specific focus on scrutinizing the differential expression patterns of growth-associated genes using RNA sequencing and quantitative real-time PCR analysis. A substantial number of genes—36,044 differentially expressed genes (DEGs)—exhibited significant differential expression between consecutive developmental stages. These DEGs were then categorized into multiple pathways (Q value < 0.05), including crucial pathways such as the spliceosome, vascular smooth muscle contraction, DNA replication, and apoptosis, among others. In addition, we identified two pivotal signaling pathways—the Hedgehog (Hh) signaling pathway and the TGF-beta (TGF-β) signaling pathway—associated with the growth and development of M. coruscus larvae. Ten key growth-related genes were pinpointed, each playing crucial roles in molecular function and the regulation of growth traits in M. coruscus. These genes and pathways associated with growth provide deep insights into the molecular basis of physiological adaptation, metabolic processes, and growth variability in marine bivalves.

NF-E2-related factor 2 (Nrf2) plays a crucial role in the oxidative regulatory process, which could trigger hundreds of antioxidant elements to confront xenobiotics. In the previous study, we identified Nrf2 from the marine mussel Mytilus coruscus, and the findings demonstrated that McNrf2 effectively protected the mussels against oxidative stress induced by benzopyrene (Bap). In order to delve deeper into the underlying mechanism, we utilized Chromatin Immunoprecipitation followed by sequencing (ChIP-seq) technology to systematically identify potential novel target genes of McNrf2. A total of 3,465 potential target genes were screened, of which 219 owned binding sites located within the promoter region. During subsequent experimental verification, it was found that McSLC35E2, a candidate target gene of McNrf2, exhibited negative regulation by McNrf2, as confirmed through dual luciferase and qRT-PCR detection. Further, the enzyme activity tests demonstrated that McNrf2 could counteract Bap induced oxidative stress by inhibiting McSLC35E2. The current study provides valuable insights into the application of ChIP-seq technology in the research of marine mollusks, advancing our understanding of the key role of Nrf2 in antioxidant defense mechanisms, and highlighting the significance of SLC35E2 in the highly sophisticated regulation of oxidative stress response in marine invertebrates.