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Related Data for: Ammonia transporter 2 as a molecular marker to elucidate the potentials of ammonia transport in phylotypes of Symbiodinium, Cladocopium and Durusdinium in the fluted giant clam, Tridacna squamosa
No full textGiant clams harbor coccoid Symbiodiniaceae dinoflagellates that are phototrophic. These dinoflagellates generally include multiple phylotypes (species) of Symbiodinium, Cladocopium, and Durusdinium in disparate proportions depending on the environmental conditions. The coccoid symbionts can share photosynthate with the clam host, which in return supply them with nutrients containing inorganic carbon, nitrogen and phosphorus. Symbionts can recycle nitrogen by absorbing and assimilating the endogenous ammonia produced by the host. This study aimed to use the transcript levels of ammonia transporter 2 (AMT2) in Symbiodinium (Symb-AMT2), Cladocopium (Clad-AMT2) and Durusdinium (Duru-AMT2) as molecular indicators to estimate the potential of ammonia transport in these three genera of Symbiodiniaceae dinoflagellates in different organs of the fluted giant clam, Tridacna squamosa, obtained from Vietnam. We also determined the transcript levels of form II ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcII) and nitrate transporter 2 (NRT2) in Symbiodinium (Symb-rbcII; Symb-NRT2), Cladocopium (Clad-rbcII; Clad-NRT2) and Durusdinium (Duru-rbcII; Duru-NRT2), in order to examine the potential of ammonia transport with reference to the potentials of phototrophy or NO₃− uptake independent of the quantities and proportion of these Symbiodiniaceae phylotypes. Our results indicated for the first time that phylotypes of Symbiodinium and Cladocopium could have different potentials of ammonia transport, and that phylotypes of Symbiodinium might have higher potential of NO₃− transport than ammonia transport. They also suggested that Symbiodiniaceae phylotypes residing in different organs of T. squamosa could have disparate potentials of ammonia transport, alluding to the functional diversity among phylotypes of coccoid Symbiodinium, Cladocopium, and Durusdinium
Related Data for: Effects of seawater acclimation on two Na+/K+-ATPase α-subunit isoforms in the gills of the marble goby, Oxyeleotris marmorata
No full textThe marble goby, Oxyeleotris marmorata, is a freshwater teleost, but can acclimate progressively to survive in seawater (salinity 30). As an obligatory air-breather, it can also survive long periods of emersion. Two isoforms of Na+/K+-ATPase (nka) α-subunit, nkaα1 and nkaα3, but not nkaα2, had been cloned from the gills of O. marmorata. The cDNA sequence of nkaα1 consisted of 3069 nucleotides, coding for 1023 amino acids (112.5 kDa), whereas nkaα3 consisted of 2976 nucleotides, coding for 992 amino acids (109.5 kDa). As only one form of branchial Nkaα1 was identified using molecular cloning in this study, O. marmorata lacks specific freshwater- and seawater-type Nkaα isoforms as demonstrated by some other euryhaline fish species. The nkaα1 transcript level was about 2.5-fold higher than that of nkaα3 in the gills of freshwater O. marmorata. During exposure to seawater, the branchial transcript level of nkaα1 increased significantly on day 1 (~3.3-fold) and day 6 (~2.6-fold). By contrast, the branchial transcript level of nkaα3 increased significantly on day 1 (~2.6-fold), but not on day 6, of seawater exposure. Six days of exposure to seawater also led to significant increases in protein abundances of Nkaα1 (~6.9-fold) and Nkaα3 (~2.8-fold) in the gills of O. marmorata. Hence, the mRNA and protein expressions of both nkaα1/Nkaα1 and nkaα3/Nkaα3 were up-regulated in O. marmorata during seawater acclimation. This could explain why Vmax increases but Km for Na+ and K+ remain unchanged in Nka extracted from the gills of O. marmorata acclimated to seawater as reported previously
Related Data for: Using transcript levels of nitrate transporter 2 as molecular indicators to estimate the potentials of nitrate transport in Symbiodinium, Cladocopium, and Durusdinium of the fluted giant clam, Tridacna squamosa
No full textGiant clams are important ecosystem engineers of coral reefs because they harbor large quantities of phototrophic Symbiodiniaceae dinoflagellates of mainly genera Symbiodinium, Cladocopium, and Durusdinium. The coccoid dinoflagellates donate photosynthate and amino acids to the clam host, which in return needs to supply inorganic carbon and nitrogen to them. The host can conduct light-enhanced absorption of nitrate (NO3–), which can only be metabolized by the symbionts. This study aimed to clone nitrate transporter 2 (NRT2) from the symbionts of the fluted giant clam, Tridacna squamosa. Here, we report three major sequences of NRT2 derived from Symbiodinium (Symb-NRT2), Cladocopium (Clad-NRT2) and Durusdinium (Duru-NRT2). Phenogramic analysis and molecular characterization confirmed that these three sequences were NRT2s derived from dinoflagellates. Immunofluorescence microscopy localized NRT2 at the plasma membrane and cytoplasmic vesicles of the symbiotic dinoflagellates, indicating that it could partake in the uptake and transport of NO3–. Therefore, the transcript levels of Symb-NRT2, Clad-NRT2, and Duru-NRT2 could be used as molecular indicators to estimate the potential of NO3– transport in five organs of 13 T. squamosa individuals. The transcript levels of form II ribulose-1, 5-bisphosphate carboxylase/oxygenase (rbcII) of Symbiodinium (Symb-rbcII), Cladocopium (Clad-rbcII) and Durusdinium (Duru-rbcII) were also determined in order to calculate the transcript ratios of Symb-NRT2/Symb-rbcII, Clad-NRT2/Clad-rbcII, and Duru-NRT2/Duru-rbcII. These ratios expressed the potentials of NO3– transport with reference to the phototrophic potentials in a certain genus of coccoid dinoflagellate independent of its quantity. Results obtained indicate that Symbiodinium generally had a higher potential of NO3– transport than Cladocopium and Durusdinium at the genus level. Furthermore, some phylotypes (species) of Symbiodinium, particularly those in the colorful outer mantle, had very high Symb-NRT2/Symb-rbcII ratio (7–13), indicating that they specialized in NO3– uptake and nitrogen metabolism. Overall, our results indicate for the first time that different phylotypes of Symbiodiniaceae dinoflagellates could have dissimilar abilities to absorb and assimilate NO3–, alluding to their functional diversity at the genus and species levels
Related Data for: Symbiotic dinoflagellates of the giant clam, Tridacna squamosa, express ammonium transporter 2 at the plasma membrane and increase its expression levels during illumination
No full textGiant clams harbor dinoflagellates generally of the three genera (Symbiodinium, Cladocopium, and Durusdinium) of phototrophic Symbiodiniaceae. Coccoid dinoflagellates (alias zooxanthellae) are found mainly inside zooxanthellal tubules located in the colorful outer mantle. The symbionts need to obtain carbon, nitrogen and phosphorus from the host for growth and metabolism. The host can absorb exogenous ammonia through the ctenidium and assimilate it into glutamine. Although the host does not normally excrete ammonia, its hemolymph contains only low concentrations of ammonia, indicating that the symbionts can absorb and recycle the ammonia produced metabolically by the host. In this study, we had obtained from the outer mantle of the giant clam, Tridacna squamosa, three major ammonium transporter 2 (AMT2) sequences, one each for Symbiodinium spp. (Symb-AMT2), Cladocopium spp. (Clad-AMT2), and Durusdinium spp. (Duru-AMT2), which comprised 1341 bp, 1308 bp, and 1296 bp, respectively. The respective deduced amino acid sequences contained 447 (~ 46.5 kDa), 436 (~ 45.5 kDa), and 432 (~ 45.0 kDa) residues. Phenogramic and sequence similarity analyses confirmed that these sequences were derived from dinoflagellates. Zooxanthellae-AMT2 (Zoox-AMT2), which represented comprehensively AMT2 of Symbiodinium spp., Cladocopium spp., and Durusdinium spp. was localized at the dinoflagellates’ plasma membranes, indicating that it could partake in the absorption of ammonia from the luminal fluid of the zooxanthellal tubules. Zoox-AMT2 expression was detected in the outer mantle, inner mantle, foot muscle, hepatopancreas and ctenidium of T. squamosa, indicating that the coccoid dinoflagellates residing in all five organs had the potential of ammonia absorption. The outer mantle had the highest transcript level of Zoox-AMT2, and illumination upregulated the protein abundance of Zoox-AMT2 therein. Therefore, it can be deduced that the coccoid dinoflagellates residing in the outer mantle could augment the potential of ammonia absorption in alignment with photosynthesis as the assimilation of ammonia required an increased supply of carbon chains
Related Data for: The non-ureogenic stinging catfish, heteropneustes fossilis, actively excretes ammonia with the help of Na+/K+-ATPase when exposed to environmental ammonia
No full textThe stinging catfish, Heteropneustes fossilis, can tolerate high concentrations of environmental ammonia. Previously, it was regarded as ureogenic, having a functional ornithine-urea cycle that could be up-regulated during ammonia-loading. However, contradictory results indicated that increased urea synthesis and switching to ureotelism could not explain its high ammonia tolerance. Hence, we re-examined the effects of exposure to 30 mmol l-1 NH4Cl on its ammonia and urea excretion rates, and its tissue ammonia and urea concentrations. Our results confirm that H. fossilis did not increase urea excretion or accumulation during 6 days of ammonia exposure, and lacked detectable carbamoyl phosphate synthetase I or III activity in its liver. However, we discovered that it could actively excrete ammonia during exposure to 8 mmol l-1 NH4Cl. As active ammonia excretion is known to involve Na+/K+-ATPase (Nka) indirectly in several ammonia-tolerant fishes, we also cloned various nkaα-subunit isoforms from the gills ofH. fossilis, and determined the effects of ammonia exposure on their branchial transcripts levels and protein abundances. Results obtained revealed the presence of five nkaα-subunit isoforms, with nkaα1b having the highest transcript level. Exposure to 30 mmol l-1 NH4Cl led to significant increases in the transcript levels of nkaα1b (on day 6) and nkaα1c1 (on day 1 and 3) as compared with the control. In addition, the protein abundances of Nkaα1c1, Nkaα1c2 and total NKAα increased significantly on day 6. Therefore, the high environmental ammonia tolerance of H. fossilis is attributable partly to its ability to actively excrete ammonia with the aid of Nka
Postprandial nitrogen metabolism and excretion in the marble goby, Oxyleotris marmorata, in freshwater or brackish water, and/or in the presence of environmental ammonia
No full textThe marble goby, O. marmorata, is a facultative air-breather capable of growing to >1 kg, and is considered a delicacy over much of eastern Asia. Feeding led to only a slight increase in plasma ammonia concentration and had no significant effect on the ammonia content in the brain of juvenile O. marmorata during the subsequent 24 h. Unlike other fishes, juvenile O. marmorata could apparently avoid postprandial ammonia toxicity, and as a result there was no increase in the brain glutamine content, which decreased significantly instead at certain post-feeding time point. Since no prominent increases in tissue glutamine and urea contents were observed after feeding despite its ability to detoxify ammonia to glutamine during emersion and its possession of a full complement of hepatic ornithine-urea cycle enzymes, it can be concluded that only a moderate amount of ammonia was produced after feeding. Traditionally, it has been accepted that excess amino acid would be degraded in the liver through transdeamination which involves the deamination of glutamate catalyzed by glutamate dehydrogenase (GDH).RP 2/06 CSF & RP 19/06 CS
CYANIDE AND HYPOXIA TOLERANCE IN THE MUDSKIPPER BOLEOPHTHALMUS BODDAERTI
No full textPh.DDOCTOR OF PHILOSOPH
Creation of interactive learning aid for teaching of animal histology practicals to facilitate blended learning
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How does the snakehead, Channa Asistica, survive during aerial exposure?
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