Browsing by Author "Poo, Jeslyn Shi Ting"
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- PublicationMetadata onlyMolecular characterization, cellular localization and light-dependent expression of dinoflagellate vacuolar-type h+-atpase (VHA) subunit B in the colourful outer mantle of the giant clam, tridacna squamosa, indicate the involvement of VHA in CO2 uptake in the photosynthesizing symbionts(2021)
;Raagavi Mani ;Boo, Mel Veen ;Poo, Jeslyn Shi Ting ;Ng, Siow Y.; Ip, Yuen KwongGiant clams are animal-dinoflagellate associations found in Indo-Pacific reef ecosystems. The clam host obtains organic nutrients from phototrophic dinoflagellates of genera Symbiodinium, Cladocopium, and Durusdinium, which reside extracellularly as symbionts (alias zooxanthellae) in the luminal fluid of zooxanthellal tubules located mainly in the colourful outer mantle. The host also needs to supply the symbionts with inorganic carbon for photosynthesis. Symbiont photosynthesis can be impeded by inhibitors of vacuolar H+-ATPase (VHA) because the host possesses a carbon concentration mechanism consisting of VHA to facilitate the supply of CO2(aq) to the symbionts. Here, we report that VHA was also expressed in dinoflagellates residing in the outer mantle of the fluted giant clam, Tridacna squamosa. Three complete cDNA coding sequences of VHA subunit B (VHA-B), one for each genus of dinoflagellate, had been obtained, and each sequence comprised 1482 bp, encoding a protein of 493 amino acids (~55 kDa). As these three sequences were highly similar, we could only design real-time PCR primers to quantify comprehensively zooxanthellae-VHA-B (Zoox-VHA-B) that represented VHA-B of all three genera of dinoflagellates. The outer mantle had the highest transcript level of Zoox-VHA-B among the three organs studied, and illumination led to a significant increase in the protein abundance of Zoox-VHA-B therein. Zoox-VHA-B was immunolocalized to intracellular vesicles, which could apparently align and fuse with the plasma membrane, in the symbiotic dinoflagellates. Overall, these results indicate that photosynthesizing symbionts could increase the capacity of H+ secretion through VHA-containing vesicles to promote the dehydration of luminal HCO3− and the absorption of CO2(aq) during illumination.WOS© Citations 2Scopus© Citations 3 79 - PublicationOpen AccessPhototrophic potential and form II ribulose-1,5-bisphosphate carboxylase/oxygenase expression in five organs of the fluted giant clam, Tridacna squamosa(2020)
;Poo, Jeslyn Shi Ting ;Choo, Celine Yen Ling ;Hiong, Kum Chew ;Boo, Mel Veen ;Wong, Wai Peng; Ip, Yuen KwongDespite living in oligotrophic tropical waters, giant clams can grow to large sizes because they live in symbiosis with extracellular phototrophic dinoflagellates (zooxanthellae) and receive photosynthates from them. The physical presence of zooxanthellae in five organs (colorful outer mantle, whitish inner mantle, ctenidium, hepatopancreas and foot muscle) of Tridacna squamosa had been confirmed by microscopy, and high densities of zooxanthellae were detected in specific regions of the inner mantle and foot muscle. Symbiotic dinoflagellates use form II ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) to fix inorganic carbon during C3 photosynthesis. Using qPCR primers that were designed comprehensively against all known zooxanthellal form II RuBisCO gene sequences (rbcII) in existing databases, we demonstrated that the outer mantle of T. squamosa (TS) had the greatest phototrophic potential as reflected by its high zooxanthellal rbcII (TSZrbcII) transcript level, which varied among different regions of the outer mantle. The other four organs also expressed moderate levels of TSZrbcII, despite the lack of iridophores and direct light exposure. Importantly, light exposure led to significant increases in the protein abundance of TSZRBCII in the outer mantle but not the other four organs. Taken together, these results indicate that organs inside the mantle cavity had low phototrophic potentials, but zooxanthellae residing inside these organs might serve some unidentified functions to benefit the host.WOS© Citations 20Scopus© Citations 20 270 89 - PublicationOpen AccessSodium-dependent phosphate transporter protein 1 is involved in the active uptake of inorganic phosphate in nephrocytes of the kidney and the translocation of Pi into the tubular epithelial cells in the outer mantle of the giant clam, Tridacna squamosa(2021)
;Ip, Yuen Kwong ;Boo, Mel Veen ;Poo, Jeslyn Shi Ting ;Wong, Wai PengGiant clams display light-enhanced inorganic phosphate (Pi) absorption, but how the absorbed (Pi) is translocated to the symbiotic dinoflagellates living extracellularly in a tubular system is unknown. They can accumulate (Pi) in the kidney, but the transport mechanism remains enigmatic. This study aimed to elucidate the possible functions of sodium-dependent phosphate transporter protein 1-homolog (PiT1-like), which co-transport Na+ and H2PO4–, in these two processes. The complete cDNA coding sequence of PiT1-like, which comprised 1,665 bp and encoded 553 amino acids (59.3 kDa), was obtained from the fluted giant clam, Tridacna squamosa. In the kidney, PiT1-like was localized in the plasma membrane of nephrocytes, and could therefore absorb (Pi) from the hemolymph. As the gene and protein expression levels of PiT1-like were up-regulated in the kidney during illumination, PiT1-like could probably increase the removal of (Pi) from the hemolymph during light-enhanced (Pi) uptake. In the ctenidial epithelial cells, PiT1-like had a basolateral localization and its expression was also light-dependent. It might function in (Pi) sensing and the absorption of (Pi) from the hemolymph when (Pi) was limiting. In the outer mantle, PiT1-like was localized in the basolateral membrane of epithelial cells forming the tertiary tubules. It displayed light-enhanced expression levels, indicating that the host could increase the translocation of Pi from the hemolymph into the tubular epithelial cells and subsequently into the luminal fluid to support increased (Pi) metabolism in the photosynthesizing dinoflagellates. Taken together, the accumulation of (Pi) in the kidney of giant clams might be unrelated to limiting the availability of (Pi) to the symbionts to regulate their population.WOS© Citations 2 316 79Scopus© Citations 2 - PublicationMetadata onlySodium-dependent phosphate transporter protein 1 is involved in the active uptake of inorganic phosphate in Nephrocytes of the kidney and the translocation of Pi into the tubular epithelial cells in the outer mantle of the giant clam, Tridacna squamosa(2022)
;Ip, Yuen Kwong ;Boo, Mel Veen ;Poo, Jeslyn Shi Ting ;Wong, Wai PengGiant clams display light-enhanced inorganic phosphate (Pi) absorption, but how the absorbed Pi is translocated to the symbiotic dinoflagellates living extracellularly in a tubular system is unknown. They can accumulate Pi in the kidney, but the transport mechanism remains enigmatic. This study aimed to elucidate the possible functions of sodium-dependent phosphate transporter protein 1-homolog (PiT1-like), which cotransport Na+ and H2PO4−, in these two processes. The complete cDNA coding sequence of PiT1-like, which comprised 1,665 bp and encoded 553 amino acids (59.3 kDa), was obtained from the fluted giant clam, Tridacna squamosa. In the kidney, PiT1-like was localized in the plasma membrane of nephrocytes, and could therefore absorb Pi from the hemolymph. As the gene and protein expression levels of PiT1-like were up-regulated in the kidney during illumination, PiT1-like could probably increase the removal of Pi from the hemolymph during light-enhanced Pi uptake. In the ctenidial epithelial cells, PiT1-like had a basolateral localization and its expression was also lightdependent. It might function in Pi sensing and the absorption of Pi from the hemolymph when Pi was limiting. In the outer mantle, PiT1-like was localized in the basolateral membrane of epithelial cells forming the tertiary tubules. It displayed light-enhanced expression levels, indicating that the host could increase the translocation of Pi from the hemolymph into the tubular epithelial cells and subsequently into the luminal fluid to support increased Pi metabolism in the photosynthesizing dinoflagellates. Taken together, the accumulation of Pi in the kidney of giant clams might be unrelated to limiting the availability of Pi to the symbionts to regulate their population.WOS© Citations 2Scopus© Citations 2 244 - PublicationOpen AccessSymbiodiniaceae dinoflagellates express urease in three subcellular compartments and upregulate its expression levels in situ in three organs of a giant clam (Tridacna squamosa) during illumination(2020)
;Ip, Yuen Kwong ;Teng, Germaine Ching Yun ;Boo, Mel Veen ;Poo, Jeslyn Shi Ting ;Hiong, Kum Chew ;Kim, Hyoju ;Wong, Wai PengGiant clams harbor three genera of symbiotic dinoflagellates (Symbiodinium, Cladocopium, Durusdinium) as extracellular symbionts (zooxanthellae). While symbiotic dinoflagellates can synthesize amino acids to benefit the host, they are nitrogen‐deficient. Hence, the host must supply them with nitrogen including urea, which can be degraded to ammonia and carbon dioxide by urease (URE). Here, we report three complete coding cDNA sequences of URE, one for each genus of dinoflagellate, obtained from the colorful outer mantle of the giant clam, Tridacna squamosa. The outer mantle had higher transcript level of Tridacna squamosa zooxanthellae URE (TSZURE) than the whitish inner mantle, foot muscle, hepatopancreas and ctenidium. TSZURE was immunolocalized strongly and atypically in the plastid, moderately in the cytoplasm, and weakly in the cell wall and plasma membrane of symbiotic dinoflagellates. In the outer mantle, illumination upregulated the protein abundance of TSZURE, which could enhance urea degradation in photosynthesizing dinoflagellates. The urea‐nitrogen released could then augment syntheses of amino acids to be shared with the host for its general needs. Illumination also enhanced gene and protein expression levels of TSZURE/TSZURE in the inner mantle and foot muscle, which contain only small quantities of symbiotic dinoflagellate, have no iridocyte, and lack direct exposure to light. With low phototrophic potential, dinoflagellates in the inner mantle and foot muscle might need to absorb carbohydrates in order to assimilate the urea‐nitrogen into amino acids. Amino acids donated by dinoflagellates to the inner mantle and the foot muscle could be used especially for syntheses of organic matrix needed for light‐enhanced shell formation and muscle protein, respectively.WOS© Citations 8 84 85Scopus© Citations 8 - PublicationOpen AccessUsing form II ribulose-1,5-bisphosphate carboxylase/oxygenase to estimate the phototrophic potentials of Symbiodinium, Cladocopium and Durusdinium in various organs of the fluted giant clam, Tridacna squamosa, and to evaluate their responses to light upon isolation from the host(2021)
;Poo, Jeslyn Shi Ting ;Boo, Mel Veen; Ip, Yuen KwongMutualistic associations with symbiotic dinoflagellates (zooxanthellae) enable invertebrate hosts to thrive in tropical waters that are shallow and oligotrophic. Giant clams can harbor multiple species of symbiotic dinoflagellates (Family: Symbiodiniaceae) from mainly three genera, Symbiodinium, Cladocopium and Durusdinium, but whether they have distinct physiological functions at the genus level in the holobiont remains unclear. As symbiotic dinoflagellates use form II ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) to fix inorganic carbon, we attempted to estimate the phototrophic potentials and thus the relative abundances of Symbiodinium, Cladocopium and Durusdinium in five organs (outer mantle, inner mantle, foot muscle, ctenidium and hepatopancreas) of the fluted giant clam Tridacna squamosa through quantitative real-time PCR (qPCR) with primers that are specific to form II RuBisCO gene sequences (rbcII) of each genus. Based on the transcript levels of rbcII derived from Symbiodinium (Symb-rbcII), Cladocopium (Clad-rbcII) and Durusdinium (Duru-rbcII), we demonstrated that the symbiont population of T. squamosa from Vietnam was dominated by Durusdinium. Furthermore, the proportion of Symb-rbcII, Clad-rbcII and Duru-rbcII, and hence the phototrophic potentials of Symbiodinium, Cladocopium and Durusdinium, varied among five organs of T. squamosa, and along the length of the outer mantle. For dinoflagellates freshly isolated from the outer mantle of T. squamosa, Symb-rbcII, Clad-rbcII and Duru-rbcII exhibited different responses to light at the transcriptional level. Importantly, these results corroborate the proposition that the association with different genera and/or species of dinoflagellates might confer distinct physiological advantages to the host clam, which differs under various environmental conditions.WOS© Citations 11Scopus© Citations 11 303 108 - PublicationOpen AccessUsing glutamine synthetase 1 to evaluate the symbionts' potential of ammonia assimilation and their responses to illumination in five organs of the giant clam, Tridacna squamosa(2021)
;Teh, Leanne S. X. ;Poo, Jeslyn Shi Ting ;Boo, Mel Veen; Ip, Yuen KwongNitrogen-deficient symbiotic dinoflagellates (zooxanthellae) living inside the fluted giant clam, Tridacna squamosa, need to obtain nitrogen from the host. Glutamine synthetase 1 (GS1) is a cytosolic enzyme that assimilates ammonia into glutamine. We determined the transcript levels of zooxanthellal GS1 (Zoox-GS1), which represented comprehensively GS1 transcripts of Symbiodinium, Cladocopium and Durusdinium, in five organs of T. squamosa. The outer mantle had significantly higher transcript level of Zoox-GS1 than the inner mantle, foot muscle, hepatopancreas and ctenidium, but the transcript ratios of Zoox-GS1 to zooxanthellal form II ribulose-1,5-bisphosphate carboxylase/oxygenase (Zoox-rbcII), which represented the potential of ammonia assimilation relative to the phototrophic potential, were comparable among these five organs. Based on transcript ratios of Zoox-GS1 to zooxanthellal Urease (Zoox-URE), the outer mantle had the highest potential of urea degradation relative to ammonia assimilation among the five organs, probably because urea degradation could furnish CO2 and NH3 for photosynthesis and amino acid synthesis, respectively, in the symbionts therein. The protein abundance of Zoox-GS1 was upregulated in the outer mantle and the inner mantle during illumination. Zoox-GS1 could catalyze light-enhanced glutamine formation using ammonia absorbed from the host or ammonia released through urea degradation in the cytoplasm. The glutamine produced could be used to synthesize other nitrogenous compounds, including amino acids in the cytoplasm or in the plastid of the dinoflagellates. Some of the amino acids synthesized by the symbionts in the inner mantle and foot muscle could be donated to the host to support shell organic matrix formation and muscle production, respectively.WOS© Citations 8Scopus© Citations 8 287 60