Physiological and biochemical responses of Dosinia corrugata to different thermal and salinity stressors

Transcriptome analysis reveals molecular mechanism of Dosinia corrugata in response to acute heat stress

This study seeks to explore the molecular regulatory mechanism within Dosinia corrugata in response to extreme high-temperature conditions, aiming to enhance the sustainable development of the D. corrugata aquaculture industry. To identify heat-responsive genes and elucidate adaptive mechanisms, we conducted transcriptional profiling of D. corrugata gills after 12 h and 24 h of acute heat stress. At 12 h and 24 h under acute heat stress, we detected 6842 and 1112 differentially expressed genes (DEGs), respectively. KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis revealed that co-enriched pathways at both time points included Apoptosis-multiple species, Ubiquitin-mediated proteolysis, Tumor Necrosis Factor (TNF) signaling pathway, and Retinoic acid-inducible Gene I (RIG-I)-like receptor signaling pathway in response to acute heat stress. It is noteworthy that at 12 h of acute heat stress, metabolic pathways were significantly enriched, while at 24 h, immune-related pathways showed significant enrichment. Based on the co-enrichment pathways identified at both time points during acute heat stress (12 h and 24 h), we constructed a potential regulatory network for differentially expressed genes under heat stress. This study offers valuable insights into comprehending the potential molecular regulatory mechanisms that underlie D. corrugata's response to elevated temperatures.

Molecular evidence for the adaptive evolution in euryhaline bivalves

Marine bivalves inhabiting intertidal and estuarine areas are frequently exposed to salinity stress due to persistent rainfall and drought. Through prolonged adaptive evolution, numerous bivalves have developed eurysalinity, which are capable of tolerating a wide range of salinity fluctuations through the sophisticated regulation of physiological metabolism. Current research has predominantly focused on investigating the physiological responses of bivalves to salinity stress, leaving a significant gap in our understanding of the adaptive evolutionary characteristics in euryhaline bivalves. Here, comparative genomics analyses were performed in two groups of bivalve species, including 7 euryhaline species and 5 stenohaline species. We identified 24 significantly expanded gene families and 659 positively selected genes in euryhaline bivalves. A significant co-expansion of solute carrier family 23 (SLC23) facilitates the transmembrane transport of ascorbic acids in euryhaline bivalves. Positive selection of antioxidant genes, such as GST and TXNRD, augments the capacity of active oxygen species (ROS) scavenging under salinity stress. Additionally, we found that the positively selected genes were significantly enriched in KEGG pathways associated with carbohydrates, lipids and amino acids metabolism (ALDH, ADH, and GLS), as well as GO terms related to transmembrane transport and inorganic anion transport (SLC22, CLCND, and VDCC). Positive selection of MCT might contribute to prevent excessive accumulation of intracellular lactic acids during anaerobic metabolism. Positive selection of PLA2 potentially promote the removal of damaged membranes lipids under salinity stress. Our findings suggest that adaptive evolution has occurred in osmoregulation, ROS scavenging, energy metabolism, and membrane lipids adjustments in euryhaline bivalves. This study enhances our understanding of the molecular mechanisms underlying the remarkable salinity adaption of euryhaline bivalves.

Transcriptome analysis reveals differential immune related genes expression in Ruditapes philippinarum under hypoxia stress: potential HIF and NF-κB crosstalk in immune responses in clam

Background

Hypoxia is an important environmental stressor in aquatic ecosystems, with increasingly impacts on global biodiversity. Benthic communities are the most sensitive parts of the coastal ecosystem to eutrophication and resulting hypoxia. As a filter-feeding organism living in the seafloor sediment, Ruditapes philippinarum represents an excellent “sentinel” species to assess the quality of marine environment. In order to gain insight into the molecular response and acclimatization mechanisms to hypoxia stress in marine invertebrates, we examined hypoxia-induced changes in immune-related gene expression and gene pathways involved in hypoxia regulation of R. philippinarum.

Results

We investigated the response of the Manila clam R. philippinarum to hypoxia under experimental conditions and focused on the analysis of the differential expression patterns of specific genes associated with hypoxia response by RNA-seq and time course qPCR analysis. A total of 75 genes were captured significantly differentially expressed, and were categorized into antioxidant/oxidative stress response, chaperones/heat shock proteins, immune alteration, and cell proliferation/apoptosis. Fourteen hypoxia responsive genes were validated significantly up/down regulated at different time 0, 2, 5, and 8 d in gills of R. philippinarum in hypoxia challenged group. Functional enrichment analysis revealed the HIF signaling pathway and NF-κB signaling pathway play pivotal roles in hypoxia tolerance and resistance in R. philippinarum.

Conclusion

The HIF signaling pathway and NF-κB signaling pathway play a critical role in hypoxia tolerance and resistance in Manila clam. The immune and defense related genes and pathways obtained here gain a fundamental understanding of the hypoxia stress in marine bivalves and provide important insights into the physiological acclimation, immune response and defense activity under hypoxia challenge. The reduced metabolism is a consequence of counterbalancing investments in immune defense against other physiological processes.

Biological and biochemical assessment in Phorcus articulatus (Lamarck 1822): contamination and seasonal effect

This work aims to diagnose the state of the northeastern coasts of Tunisia using P. articulatus species. Biological parameters, protein and metallothionein content, enzymatic activities, and metallic concentration were assessed at four stations during four seasons and analyzed by multiple regressions. The comparison of biological ratios showed minima at Sidi Daoued and maxima at Korbous where metallothioneins were maximal. The catalytic activity was low during summer and higher during cold periods contrary to acetylcholinesterase activity. Concerning glutathione S-transferase, its activity was important at Kelibia in autumn and at La Goulette and Sidi Daoued in warm seasons. The metallic concentrations were low at Korbous and maximal at Kelibia and Sidi Daoued stations. Kelibia seems to be the most polluted site followed by Sidi Daoued and La Goulette (industries, urbanization and fishing ports). The pollution seems to be reduced at Korbous station having more suitable conditions for the proliferation of monodonts.