Myostatin, also known as GDF8, is a member of the transforming growth factor-β (TGF-β) superfamily. In vertebrates, myostatin negatively regulates the growth of skeletal muscle. In invertebrates, it has been reported to be closely related to animal growth. However, knowledge concerning the molecular mechanisms involved in the myostatin regulation of molluscan growth is limited. In this study, we found that the hdh-myostatin open reading frame (ORF) comprised 1470 base pairs that encoded 489 amino acids and contained structural characteristics typical of the TGF-β superfamily, including a C-terminal signal peptide, a propeptide domain, and TGF-β region. Gene expression analysis revealed that hdh-myostatin mRNA was widely expressed at different levels in all of the examined tissues of Haliotis discus hannai. Nine single nucleotide polymorphisms (SNPs) were associated with the growth traits. RNA interference (RNAi) against hdh-myostatin mRNA significantly downregulated hdh-myostatin at days 1, 15, and 30 post injection, and the pattern was correlated with downregulation of the genes TGF-β receptor type-I (hdh-TβR I), activin receptor type-IIB (hdh-ActR IIB), and mothers against decapentaplegic 3 (hdh-Smad3). After one month of the RNAi experiment, the shell lengths and total weights increased in the abalone, Haliotis discus hannai. The results of qRT-PCR showed that the hdh-myostatin mRNA level was higher in the slow-growing group than in the fast-growing group. These results suggest that hdh-myostatin is involved in the regulation of growth, and that these SNPs would be informative for further studies on selective breeding in abalone.

Bone morphogenetic proteins (BMPs) play important roles in a lot of biological processes, such as bone development, cell proliferation, cell differentiation, growth, etc. However, the functions of abalone BMP genes are still unknown. This study aimed to better understand the characterization and biological function of BMP7 of Haliotis discus hannai (hdh-BMP7) via cloning and sequencing analysis. The coding sequence (CDS) length of hdh-BMP7 is 1251 bp, which encodes 416 amino acids including a signal peptide (1–28 aa), a transforming growth factor-β (TGF-β) propeptide (38–272 aa), and a mature TGF-β peptide (314–416 aa). The analysis of expression showed that hdh-BMP7 mRNA was widely expressed in all the examined tissues of H. discus hannai. Four SNPs were related to growth traits. The results of RNA interference (RNAi) showed that the mRNA expression levels of hdh-BMPR I, hdh-BMPR II, hdh-smad1, and hdh-MHC declined after hdh-BMP7 was silenced. After RNAi experiment for 30 days, the shell length, shell width, and total weight were found to be reduced in H. discus hannai (p < 0.05). The results of real-time quantitative reverse transcription PCR revealed that the hdh-BMP7 mRNA was lower in abalone of the S-DD-group than in the L-DD-group. Based on these data, we hypothesized that BMP7 gene has a positive role in the growth of H. discus hannai.

Abalone is a popular mollusk in the marine aquaculture industry of China. However, existing challenges, like slow growth, individual miniaturization, and the absence of abundant abalone, have emerged as significant obstacles impeding its long-term progress in aquaculture. Studies have demonstrated that insulin-related peptide (IRP) is a crucial factor in the growth of marine organisms. However, limited studies have been conducted on IRP in abalone. This study indicated that the hdh-MIRP1 open reading frame (ORF) was composed of 456 base pairs, which encoded 151 amino acids. Based on the gene expression and immunofluorescence analyses, the cerebral ganglion of Haliotis discus hannai (H. discus hannai) was the primary site of hdh-MIRP1 mRNA expression. Moreover, hdh-MIRP1 expression was observed to be higher in the larger group than in the smaller group abalones. Only single nucleotide polymorphism (SNP) was related to their growth characteristics. However, approximately 82 proteins that may interact with hdh-MIRP1 were identified. The functional enrichment analysis of the 82 genes indicated that hdh-MIRP1 may be involved in the regulation of glucose metabolism and the process of growth. This study established a benchwork for further investigating the role of IRP in the growth of abalone.

Reproduction and breeding are crucial to maintaining abalone aquaculture. Understanding the molecular underpinnings of sexual maturation is essential for advancing knowledge in reproductive biology. However, the molecular mechanisms of gonadal development in abalones remain poorly understood, particularly in microRNA (miRNA)-mediated regulation. Thus, this study conducted a comprehensive transcriptomic analysis of abalone Haliotis discus hannai (H. discus hannai) to identify genes and miRNAs associated with ovarian and testicular discovery. This study identified 685 differentially expressed (DE) genes between the H. discus hannai ovary (DD_ovary) and testis (DD_testis) groups, comprising 479 upregulated and 206 downregulated genes in the DD_ovary. Moreover, 137 miRNAs, including 83 novel and 54 known miRNAs, were detected, with 30 upregulated and 27 downregulated in the DD_ovary compared to the DD_testis. Bioinformatics analysis revealed that these miRNAs regulate key processes such as carbohydrate metabolic processes, kinase and hydrolase activity, and starch and sucrose metabolism, all potentially associated with reproductive traits. Further, key mRNA candidates, including Vitelline envelope sperm lysin receptor (Verl) and Testis-specific serine/threonine-protein kinase (Tssk) 1, and miRNAs such as novel_90 and novel_120, were identified as components of a functional miRNA-mRNA network associated with sexual maturity and sex determination. These key genes were verified using qRT-PCR and fluorescence in situ hybridization (FISH). These transcriptomic and miRNA datasets provide valuable resources for understanding abalone reproductive biology and may support molecular breeding strategies.

Most benthic marine invertebrates exhibit a characteristic biphasic life cycle, consisting of a planktonic larval stage followed by a benthic adult stage

(1) Background: Animal growth is a complex process, involving the coordination of a wide variety of genes, non-coding RNAs, and pathways. Circular RNAs (circRNAs) belong to a novel class of functional non-coding RNAs (ncRNAs). They have a distinctive ring structure and are involved in various biological processes, including the proliferation, differentiation, and apoptosis of muscle cells. The Pacific abalone Haliotis discus hannai is an economically valuable mollusk species cultivated in China. However, the modulation of muscle growth by circRNAs in this species is poorly understood. (2) Methods: In this study, we analyzed the muscle transcriptomes of 6 H. discus hannai specimens: three small (S_HD) and three large (L_HD) groups via RNA-seq and bioinformatics technology. (3) Results: The results indicated the presence of 11,744 circRNAs in abalone adductor muscle. Furthermore, the L_HD group had 250 significantly differentially expressed circRNAs (106 upregulated and 144 downregulated) relative to the S_HD group. Moreover, the bioinformatics assessment revealed that circRNAs were related to lipid transporter activity, lipid biosynthetic process, fat digestion and absorption, the single-organism metabolic process, the thyroid hormone signaling pathway, and the hippo signaling pathway, which regulates growth. Seventeen key candidate circRNAs were identified, and a core functional circRNA-miRNA-mRNA network associated with abalone muscle growth was described. Gene expression was verified using qRT-PCR, confirming the accuracy of the RNA-seq data. (4) Conclusion: Overall, this investigation furnishes novel evidence for the potential muscle growth modulatory mechanisms in Pacific abalone. These high-quality circRNA data of abalone muscle provide a reference for functional studies on the abalone genome.