Multiple calmodulin genes of the Pacific abalone, Haliotis discus hannai (Mollusca: Vetigastropoda: Haliotidae)

Comparative analysis of the heart histological structure, metabolic enzyme activities and transcriptome profiles of juvenile and adult yellowfin tuna (Thunnus albacares) in the South China Sea

The yellowfin tuna is a large marine carnivorous fish with high commercial value. It is known for its unique physiological characteristics and holds significant potential for aquaculture. However, research on this species' developmental biology and physiology remains limited, particularly regarding the structural characteristics and functional changes in the developing heart. To investigate the differences in cardiac tissue structure and function at different developmental stages in yellowfin tuna, we conducted comparative analyses of histology, metabolic enzyme activity, and transcriptomes. Hematoxylin and eosin (H&E) and Masson staining revealed that cardiac muscle fibers were thicker and more compact, and the area of collagen fibers was significantly increased in adult fish compared to juvenile fish (p < 0.001). Additionally, the enzyme activities of Na+K+-ATPase, Ca2+Mg2+-ATPase, carnitine palmitoyltransferase 1 (CPT-1), lactate dehydrogenase (LDH), succinate dehydrogenase (SDH), and malate dehydrogenase (MDH) were notably greater in adult fish compared to juvenile fish (p < 0.05). Comparative transcriptome analysis identified 1293 differentially expressed genes (DEGs) between juvenile and adult fish. Functional enrichment analyses indicated that these differential genes are primarily closely associated with heart development and metabolic regulation pathways. Furthermore, key metabolism-related DEGs, such as acsl3b, acsbg2, acsl1a, and cpt1ab, were further identified, and quantitative real-time PCR (qRT-PCR) validated the accuracy of the results. In conclusion, this study provides a systematic analysis of the differences in histology, metabolic enzyme activities, and transcriptomics between the hearts of juvenile and adult yellowfin tuna, providing foundational data for future research on heart development in the later stages of yellowfin tuna and contributing to the advancement of aquaculture practices for this species.

Molecular characterization and gene expression of pattern recognition receptors in brown-marbled grouper (Epinephelus fuscoguttatus) fingerlings responding to vibriosis infection

The pathogen recognition system involves receptors and genes that play a crucial role in activating innate immune response in brown-marbled grouper (Epinephelus fuscoguttatus) as a control agent against various infections including vibriosis. Here, we report the molecular cloning of partial open reading frames, sequences characterization, and expression profiles of Pattern Recognition Receptors (PRRs) in brown-marbled grouper. The PRRs, namely pglyrp5, tlr5, ctlD, and ctlE in brown-marbled grouper, possess conserved domains and showed shared evolutionary relationships with other fishes, humans, mammals, birds, reptilians, amphibians, and insects. In infection experiments, up to 50% mortality was found in brown-marbled grouper fingerlings infected with Vibrio alginolyticus compared to 27% mortality infected Vibrio parahaemolyticus and 100% survival of control groups. It is also demonstrated that all four PRRs had higher expression in samples infected with V. alginolyticus compared to V. parahaemolyticus. This PRRs gene expression analysis revealed that all four PRRs expressed rapidly at 4-h post-inoculation even though the Vibrio count was only detected earliest at 12-h post-inoculation in samples. The highest expression recorded was from V. alginolyticus inoculated fish spleen with up to 73-fold change for pglyrp5 gene, followed by 14 to 38-fold expression for the same treatment in spleen, head kidney, and blood samples for other PRRs, namely tlr5, ctlD, and ctlE genes. Meanwhile less than a 10% increase in expression of all four genes was detected in spleen, head kidney, and blood samples inoculated with V. parahaemolyticus. These findings indicated that pglyrp5, tlr5, ctlD, and ctlE play important roles in the early immune response to vibriosis infected, brown-marbled grouper fingerlings.

Spatial-temporal expression analysis of lineage-restricted shell matrix proteins reveals shell field regionalization and distinct cell populations in the slipper snail Crepidula atrasolea

Molluscs are one of the most morphologically diverse clades of metazoans, exhibiting an immense diversification of calcium carbonate structures, such as the shell. Biomineralization of the calcified shell is dependent on shell matrix proteins (SMPs). While SMP diversity is hypothesized to drive molluscan shell diversity, we are just starting to unravel SMP evolutionary history and biology. Here we leveraged two complementary model mollusc systems, Crepidula fornicata and Crepidula atrasolea , to determine the lineage-specificity of 185 Crepidula SMPs. We found that 95% of the adult C. fornicata shell proteome belongs to conserved metazoan and molluscan orthogroups, with molluscan-restricted orthogroups containing half of all SMPs in the shell proteome. The low number of C. fornicata -restricted SMPs contradicts the generally-held notion that an animal’s biomineralization toolkit is dominated by mostly novel genes. Next, we selected a subset of lineage-restricted SMPs for spatial-temporal analysis using in situ hybridization chain reaction (HCR) during larval stages in C. atrasolea . We found that 12 out of 18 SMPs analyzed are expressed in the shell field. Notably, these genes are present in 5 expression patterns, which define at least three distinct cell populations within the shell field. These results represent the most comprehensive analysis of gastropod SMP evolutionary age and shell field expression patterns to date. Collectively, these data lay the foundation for future work to interrogate the molecular mechanisms and cell fate decisions underlying molluscan mantle specification and diversification.

Transcriptome analysis reveals fluid shear stress (FSS) and atherosclerosis pathway as a candidate molecular mechanism of short-term low salinity stress tolerance in abalone

BACKGROUND

Transcriptome sequencing is an effective tool to reveal the essential genes and pathways underlying countless biotic and abiotic stress adaptation mechanisms. Although severely challenged by diverse environmental conditions, the Pacific abalone Haliotis discus hannai remains a high-value aquaculture mollusk and a Chinese predominantly cultured abalone species. Salinity is one of such environmental factors whose fluctuation could significantly affect the abalone's cellular and molecular immune responses and result in high mortality and reduced growth rate during prolonged exposure. Meanwhile, hybrids have shown superiority in tolerating diverse environmental stresses over their purebred counterparts and have gained admiration in the Chinese abalone aquaculture industry. The objective of this study was to investigate the molecular and cellular mechanisms of low salinity adaptation in abalone. Therefore, this study used transcriptome analysis of the gill tissues and flow cytometric analysis of hemolymph of H. discus hannai (DD) and interspecific hybrid H. discus hannai ♀ x H. fulgens ♂ (DF) during low salinity exposure. Also, the survival and growth rate of the species under various salinities were assessed.

RESULTS

The transcriptome data revealed that the differentially expressed genes (DEGs) were significantly enriched on the fluid shear stress and atherosclerosis (FSS) pathway. Meanwhile, the expression profiles of some essential genes involved in this pathway suggest that abalone significantly up-regulated calmodulin-4 (CaM-4) and heat-shock protein90 (HSP90), and significantly down-regulated tumor necrosis factor (TNF), bone morphogenetic protein-4 (BMP-4), and nuclear factor kappa B (NF-kB). Also, the hybrid DF showed significantly higher and sustained expression of CaM and HSP90, significantly higher phagocytosis, significantly lower hemocyte mortality, and significantly higher survival at low salinity, suggesting a more active molecular and hemocyte-mediated immune response and a more efficient capacity to tolerate low salinity than DD.

CONCLUSIONS

Our study argues that the abalone CaM gene might be necessary to maintain ion equilibrium while HSP90 can offset the adverse changes caused by low salinity, thereby preventing damage to gill epithelial cells (ECs). The data reveal a potential molecular mechanism by which abalone responds to low salinity and confirms that hybridization could be a method for breeding more stress-resilient aquatic species.