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PMID:23297242
| Citation |
Nakajima, K, Tanaka, A and Matsuda, Y (2013) SLC4 family transporters in a marine diatom directly pump bicarbonate from seawater. Proc. Natl. Acad. Sci. U.S.A. 110:1767-72 |
|---|---|
| Abstract |
Photosynthesis in marine diatoms is a vital fraction of global primary production empowered by CO(2)-concentrating mechanisms. Acquisition of HCO(3)(-) from seawater is a critical primary step of the CO(2)-concentrating mechanism, allowing marine photoautotrophic eukaryotes to overcome CO(2) limitation in alkaline high-salinity water. However, little is known about molecular mechanisms governing this process. Here, we show the importance of a plasma membrane-type HCO(3)(-) transporter for CO(2) acquisition in a marine diatom. Ten putative solute carrier (SLC) family HCO(3)(-) transporter genes were found in the genome of the marine pennate diatom Phaeodactylum tricornutum. Homologs also exist in marine centric species, Thalassiosira pseudonana, suggesting a general occurrence of SLC transporters in marine diatoms. Seven genes were found to encode putative mammalian-type SLC4 family transporters in P. tricornutum, and three of seven genes were specifically transcribed under low CO(2) conditions. One of these gene products, PtSLC4-2, was localized at the plasmalemma and significantly stimulated both dissolved inorganic carbon (DIC) uptake and photosynthesis in P. tricornutum. DIC uptake by PtSLC4-2 was efficiently inhibited by an anion-exchanger inhibitor, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, in a concentration-dependent manner and highly dependent on Na(+) ions at concentrations over 100 mM. These results show that DIC influx into marine diatoms is directly driven at the plasmalemma by a specific HCO(3)(-) transporter with a significant halophilic nature. |
| Links |
PubMed PMC3562803 Online version:10.1073/pnas.1216234110 |
| Keywords |
4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid/pharmacology; Amino Acid Sequence; Bicarbonates/metabolism; Biological Transport/drug effects; Carbon/metabolism; Carbon Dioxide/metabolism; Cell Membrane/metabolism; Diatoms/genetics; Diatoms/metabolism; Diatoms/physiology; Dose-Response Relationship, Drug; Gene Expression; Kinetics; Membrane Transport Proteins/classification; Membrane Transport Proteins/genetics; Membrane Transport Proteins/metabolism; Microscopy, Confocal; Models, Biological; Molecular Sequence Data; Photosynthesis/drug effects; Phylogeny; Protein Isoforms/genetics; Protein Isoforms/metabolism; Reverse Transcriptase Polymerase Chain Reaction; Seawater/chemistry; Sequence Homology, Amino Acid |
| edit table |
Significance
Annotations
| Gene product | Qualifier | GO Term | Evidence Code | with/from | Aspect | Extension | Notes | Status |
|---|---|---|---|---|---|---|---|---|
|
part_of |
GO:0005886: plasma membrane |
ECO:0000314: direct assay evidence used in manual assertion |
C |
Seeded From UniProt |
complete | |||
| GO:0005886: plasma membrane |
ECO:0000314: |
C |
Figure 2 B, C and D show that upon fusing the ptSLC4-2 transporter to GFP, it is shown to be localized to the plasmalemma (the same thing as the plasma membrane). Figure 2C shows that ptSLC4-2 is not localized to the nucleus or the chloroplast, and Figure 2D shows that it is localized instead to the plasmalemma. |
complete | ||||
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