Please use this identifier to cite or link to this item: https://doi.org/10.1016/j.gene.2019.02.009
Title: Molecular characterization, cellular localization, and light-enhanced expression of Beta-Na + /H + Exchanger-like in the whitish inner mantle of the giant clam, Tridacna squamosa, denote its role in light-enhanced shell formation
Authors: Cao-Pham A.H. 
Hiong K.C. 
Boo M.V. 
Choo C.Y.L. 
Pang C.Z.
Wong W.P. 
Neo M.L. 
Chew S.F.
Ip Y.K. 
Keywords: Acid-base balance
Calcification
Inorganic carbon
Proton
Tridacnid
Zooxanthellae
Issue Date: 2019
Publisher: Elsevier B.V.
Citation: Cao-Pham A.H., Hiong K.C., Boo M.V., Choo C.Y.L., Pang C.Z., Wong W.P., Neo M.L., Chew S.F., Ip Y.K. (2019). Molecular characterization, cellular localization, and light-enhanced expression of Beta-Na + /H + Exchanger-like in the whitish inner mantle of the giant clam, Tridacna squamosa, denote its role in light-enhanced shell formation. Gene 695 : 101-112. ScholarBank@NUS Repository. https://doi.org/10.1016/j.gene.2019.02.009
Abstract: The fluted giant clam, Tridacna squamosa, lives in symbiosis with photosynthetic zooxanthellae, and can engage in light-enhanced growth and shell deposition. Light-enhanced shell formation necessitates the elimination of excess H+ from the extrapallial fluid adjacent to the shell. This study aimed to clone Na+/H+ Exchanger (NHE) from the whitish inner mantle adjacent to the extrapallial fluid of T. squamosa, to determine its cellular and subcellular localization, and to evaluate the effect of light exposure on its mRNA expression level and protein abundance. The complete coding cDNA sequence of NHE obtained was identified as a homolog of beta NHE (βNHE-like). It consisted of 2,925 bp, encoding for a polypeptide of 974 amino acid and 107.1 kDa, and was expressed predominantly in the inner mantle. In the inner mantle, βNHE-like was localized in the apical membrane of the seawater-facing epithelium by immunofluorescence microscopy. After exposure to light for 12 h, the seawater-facing epithelium of the inner mantle displayed consistently stronger immunostaining than that of the control exposed to 12 h of darkness. Western blotting confirmed that light exposure significantly enhanced the protein abundance of βNHE-like in the inner mantle. These results denote that some of the excess H+ generated during light-enhanced shell formation can be excreted through the light-dependent βNHE-like of the seawater-facing epithelium to minimize the impact on the whole-body pH. Importantly, the excreted H+ could dehydrate exogenous HCO3‒, and facilitate the absorption of inorganic carbon through the seawater-facing epithelia dedicated for light-enhanced shell formation due to its close proximity with the shell-facing epithelia.
Source Title: Gene
URI: https://scholarbank.nus.edu.sg/handle/10635/167888
ISSN: 03781119
DOI: 10.1016/j.gene.2019.02.009
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