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Nawaly H, Matsui H, Tsuji Y, Iwayama K, Ohashi H, Nakajima K, Matsuda Y. Multiple plasma membrane SLC4s contribute to external HCO3- acquisition during CO2 starvation in the marine diatom Phaeodactylum tricornutum. J Exp Bot 2023; 74:296-307. [PMID: 36124754 DOI: 10.1093/jxb/erac380] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Accepted: 09/16/2022] [Indexed: 06/15/2023]
Abstract
The availability of CO2 is one of the restrictions on aquatic photosynthesis. Solute carrier (SLC) 4-2, a plasma membrane HCO3- transporter has previously been identified in the marine diatom Phaeodactylum tricornutum. In this study, we discovered two paralogs, PtSLC4-1 and PtSLC4-4, that are both localized at the plasma membrane. Their overexpression stimulated HCO3- uptake, and this was inhibited by the anion channel blocker 4,4´-diisothiocyanostilbene-2,2´-disulfonic (DIDS). Similarly to SLC4-2, PtSLC4-1 specifically required Na+ of ~100 mM for its maximum HCO3- transport activity. Unlike PtSLC4-1 and PtSLC4-2, the HCO3- transport of PtSLC4-4 depended equally on Na+, K+, or Li+, suggesting its broad selectivity for cations. Transcript analyses indicated that PtSLC4-1 was the most abundant HCO3- transporter under CO2 concentrations below atmospheric levels, while PtSLC4-4 showed little transcript induction under atmospheric CO2 but transient induction to comparable levels to PtSLC4-1 during the initial acclimation stage from high CO2 (1%) to very low CO2 (<0.002%). Our results strongly suggest a major HCO3- transport role of PtSLC4-1 with a relatively minor role of PtSLC4-2, and that PtSLC4-4 operates under severe CO2 limitation unselectively to cations when the other SLC4s do not function to support HCO3- uptake.
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Affiliation(s)
- Hermanus Nawaly
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330, Japan
| | - Hiroaki Matsui
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330, Japan
| | - Yoshinori Tsuji
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330, Japan
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
| | - Kazufumi Iwayama
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330, Japan
| | - Hiroki Ohashi
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330, Japan
| | - Kensuke Nakajima
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330, Japan
| | - Yusuke Matsuda
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330, Japan
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