Posts Tagged 'molecular biology'

Ocean acidification impacts spine integrity but not regenerative capacity of spines and tube feet in adult sea urchins

Increasing atmospheric carbon dioxide (CO2) has resulted in a change in seawater chemistry and lowering of pH, referred to as ocean acidification. Understanding how different organisms and processes respond to ocean acidification is vital to predict how marine ecosystems will be altered under future scenarios of continued environmental change. Regenerative processes involving biomineralization in marine calcifiers such as sea urchins are predicted to be especially vulnerable. In this study, the effect of ocean acidification on regeneration of external appendages (spines and tube feet) was investigated in the sea urchin Lytechinus variegatus exposed to ambient (546 µatm), intermediate (1027 µatm) and high (1841 µatm) partial pressure of CO2 (pCO2) for eight weeks. The rate of regeneration was maintained in spines and tube feet throughout two periods of amputation and regrowth under conditions of elevated pCO2. Increased expression of several biomineralization-related genes indicated molecular compensatory mechanisms; however, the structural integrity of both regenerating and homeostatic spines was compromised in high pCO2 conditions. Indicators of physiological fitness (righting response, growth rate, coelomocyte concentration and composition) were not affected by increasing pCO2, but compromised spine integrity is likely to have negative consequences for defence capabilities and therefore survival of these ecologically and economically important organisms.

Continue reading ‘Ocean acidification impacts spine integrity but not regenerative capacity of spines and tube feet in adult sea urchins’

A carbonic anhydrase serves as an important acid-base regulator in Pacific oyster Crassostrea gigas exposed to elevated CO2: implication for physiological responses of mollusk to ocean acidification

Carbonic anhydrases (CAs) have been demonstrated to play an important role in acid-base regulation in vertebrates. However, the classification and modulatory function of CAs in marine invertebrates, especially their responses to ocean acidification remain largely unknown. Here, a cytosolic α-CA (designated as CgCAII-1) was characterized from Pacific oyster Crassostrea gigas and its molecular activities against CO2 exposure were investigated. CgCAII-1 possessed a conserved CA catalytic domain, with high similarity to invertebrate cytoplasmic or mitochondrial α-CAs. Recombinant CgCAII-1 could convert CO2 to HCO3− with calculated activity as 0.54 × 103 U/mg, which could be inhibited by acetazolamide (AZ). The mRNA transcripts of CgCAII-1 in muscle, mantle, hepatopancreas, gill, and hemocytes increased significantly after exposure to elevated CO2. CgCAII-1 could interact with the hemocyte membrane proteins and the distribution of CgCAII-1 protein became more concentrated and dense in gill and mantle under CO2 exposure. The intracellular pH (pHi) of hemocytes under CO2 exposure increased significantly (p < 0.05) and CA inhibition reduced the pHi value. Besides, there was no increase in CA activity in gill and mantle after CO2 exposure. The impact of CO2 exposure on CA activity coupled with the mRNA expression level and protein translocation of CgCAII-1 provided evidences that CgCAII-1 could respond to ocean acidification and participate in acid-base regulation. Such cytoplasmic CA-based physiological regulation mechanism might explain other physiological responses of marine organisms to OA.

Continue reading ‘A carbonic anhydrase serves as an important acid-base regulator in Pacific oyster Crassostrea gigas exposed to elevated CO2: implication for physiological responses of mollusk to ocean acidification’

Large-scale seaweed cultivation diverges water and sediment microbial communities in the coast of Nan’ao Island, South China Sea

Seaweed cultivation not only provides economy benefits, but also remediates the environment contaminated by mariculture of animals (e.g., fish, shrimps). However, the response of microbial communities to seaweed cultivation is poorly understood. In this study, we analyzed the diversity, composition, and structure of water and sediment microbial communities at a seaweed, Gracilaria lemaneiformis, cultivation zone and a control zone near Nan’ao Island, South China Sea by MiSeq sequencing of 16S rRNA gene amplicons. We found that large-scale cultivation of G. lemaneiformis increased dissolved oxygen (DO) and pH but decreased inorganic nutrients, possibly due to nutrient uptake, photosynthesis and other physiological processes of G. lemaneiformis. These environmental changes significantly (adonis, P < 0.05) shifted the microbial community composition and structure of both water column and sediment samples in the G. lemaneiformis cultivation zone, compared to the control zone. Also, certain microbial taxa associated with seaweed, such as Arenibacter, Croceitalea, Glaciecola, Leucothrix and Maribacter were enriched at the cultivation zone. In addition, we have proposed a conceptual model to summarize the results in this study and guide future studies on relationships among seaweed processes, microbial communities and their environments. Thus, this study not only provides new insights into our understanding the effect of G. lemaneiformis cultivation on microbial communities, but also guides future studies on coastal ecosystems.

Continue reading ‘Large-scale seaweed cultivation diverges water and sediment microbial communities in the coast of Nan’ao Island, South China Sea’

Effect of pH on temperature controlled degradation of reactive oxygen species, heat shock protein expression, and mucosal immunity in the sea cucumber Isostichopus badionotus

This study evaluated the effect of pH on the activity of antioxidant and immune enzymes in the sea cucumber Isostichopus badionotus exposed to different temperatures. The organisms (530 ±110 g) were exposed to 16, 20, 24, 28, 30, 34 and 36°C for 6 h to evaluate thermal limits at two water pH values (treatment = 7.70; control = 8.17). For the thermal tolerance experiment, the organisms were exposed to sublethal temperature of 34°C for 3, 6, 12, 24, and 48 h. I. badionotus showed signs of thermal stress by synthesizing heat shock protein 70 (hsp70) at the cold (16°C) and warm thermal limits (34°C). The glutathione peroxidase (GPx) showed a negative correlation with superoxide dismutase (SOD) activity in modulating the effect of oxidative stress at different temperature levels. Specifically, GPx activity was maximal at the extremes of the cold and warm temperatures (16, 20, and 36°C) tested, while contrarily, the SOD activity increased significantly in the narrow range of temperature between 28 and 30°C, as a part of a reaction to offset oxidative damage. The effect of pH on the expression of hsp70 was not significant, whereas the antioxidant enzymes activity was stimulated at pH 7.70. Mucosal immunity, evidenced by the activation of the phenoloxidase (PO) system, increased above the basal level at pH 7.70 and at 28, 30, and 34°C. Independent of pH, the temperature of 34°C was identified as the 12 h-sublethal upper limit for I. badionotus.

Continue reading ‘Effect of pH on temperature controlled degradation of reactive oxygen species, heat shock protein expression, and mucosal immunity in the sea cucumber Isostichopus badionotus’

Global proteome profiling of a marine copepod and the mitigating effect of ocean acidification on mercury toxicity after multigenerational exposure

Previously, we found that ocean acidification (OA) mitigates mercury (Hg) toxicity to marine copepod Tigriopus japonicus under multigenerational exposure (four generations, F0-F3). To determine the response mechanisms of T. japonicus against long-term exposure to OA and Hg pollution, we investigated the proteome of F3 copepods after multigenerational exposure to four conditions: pCO2 400 μatm + control; pCO2 1000 μatm + control; pCO2 400 μatm + 1.0 µg/L Hg; and pCO2 1000 μatm + 1.0 µg/L Hg. Functional enrichment analysis indicated that OA enhanced the copepod’s energy production mainly by increasing protein assimilation and proteolysis as a compensatory strategy, which explained its physiological resilience to reduced pH. Conversely, Hg treatment decreased many critical processes, including ferric iron binding, antioxidant activity, cellular homeostasis, and glutathione metabolism, and these toxic events could translate into higher-level responses, i.e., restrained reproduction in copepods. Importantly, the mediation of Hg toxicity in T. japonicus by OA could be explained by the enhanced lysosome-autophagy pathway proteomes that are responsible for repairing/removing damaged proteins/enzymes under stress. Overall, this study provided molecular insights into the response of T. japonicus to long-term exposure of OA and Hg, with a particular emphasis on the mitigating impact of CO2-driven acidification on Hg toxicity.

Continue reading ‘Global proteome profiling of a marine copepod and the mitigating effect of ocean acidification on mercury toxicity after multigenerational exposure’

Carbon dioxide induced plasticity of branchial acid-base pathways in an estuarine teleost

Anthropogenic CO2 is expected to drive ocean pCO2 above 1,000 μatm by 2100 – inducing respiratory acidosis in fish that must be corrected through branchial ion transport. This study examined the time course and plasticity of branchial metabolic compensation in response to varying levels of CO2 in an estuarine fish, the red drum, which regularly encounters elevated CO2 and may therefore have intrinsic resilience. Under control conditions fish exhibited net base excretion; however, CO2 exposure resulted in a dose dependent increase in acid excretion during the initial 2 h. This returned to baseline levels during the second 2 h interval for exposures up to 5,000 μatm, but remained elevated for exposures above 15,000 μatm. Plasticity was assessed via gene expression in three CO2 treatments: environmentally realistic 1,000 and 6,000 μatm exposures, and a proof-of-principle 30,000 μatm exposure. Few differences were observed at 1,000 or 6,000 μatm; however, 30,000 μatm stimulated widespread up-regulation. Translocation of V-type ATPase after 1 h of exposure to 30,000 μatm was also assessed; however, no evidence of translocation was found. These results indicate that red drum can quickly compensate to environmentally relevant acid-base disturbances using baseline cellular machinery, yet are capable of plasticity in response to extreme acid-base challenges.

Continue reading ‘Carbon dioxide induced plasticity of branchial acid-base pathways in an estuarine teleost’

Assembly of a reference transcriptome for the gymnosome pteropod Clione limacina and profiling responses to short-term CO2 exposure

The gymnosome (unshelled) pteropod Clione limacina is a pelagic predatory mollusc found in polar and sub-polar regions. It has been studied for its distinctive swimming behavior and as an obligate predator on the closely related thecosome (shelled) pteropods. As concern about ocean acidification increases, it becomes useful to compare the physiological responses of closely-related calcifying and non-calcifying species to acidification. The goals of this study were thus to generate a reference transcriptome for Clione limacina, to expose individuals to CO2 for a period of 3 days, and to explore differential patterns of gene expression. Our Trinity assembly contained 300,994 transcripts of which ~ 26% could be annotated. In total, only 41 transcripts were differentially expressed following the CO2 treatment, consistent with a limited physiological response of this species to short-term CO2 exposure. The differentially expressed genes identified in our study were largely distinct from those identified in previous studies of thecosome pteropods, although some similar transcripts were identified, suggesting that comparison of these transcriptomes and responses may provide insight into differences in responses to ocean acidification among phylogenetically and functionally distinct molluscan lineages.

Continue reading ‘Assembly of a reference transcriptome for the gymnosome pteropod Clione limacina and profiling responses to short-term CO2 exposure’


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Ocean acidification in the IPCC AR5 WG II

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