Details

Autor(en) / Beteiligte

• Nakajima, Kensuke
• Tanaka, Atsuko
• Matsuda, Yusuke

Titel

SLC4 family transporters in a marine diatom directly pump bicarbonate from seawater

Ist Teil von

• Proceedings of the National Academy of Sciences - PNAS, 2013-01, Vol.110 (5), p.1767-1772

Ort / Verlag

Washington, DC: National Academy of Sciences

Erscheinungsjahr

2013

Link zum Volltext

Quelle

MEDLINE

Beschreibungen/Notizen

• 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.