This Article Full Text Full Text (PDF) All Versions of this Article: 141/2/731    most recent pp.106.079616v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Chen, X. Articles by Shao, J.Z. Search for Related Content PubMed PubMed Citation Articles by Chen, X. Articles by Shao, J.Z. Agricola Articles by Chen, X. Articles by Shao, J.Z.

BIOENERGETICS AND PHOTOSYNTHESIS

Evidence for K⁺-Dependent HCO₃^– Utilization in the Marine Diatom Phaeodactylum tricornutum¹

Department of Biology and Hubei Key Laboratory of Bioanalytical Technique, Hubei Normal University, Huangshi 435002, Hubei, China

Photosynthetic utilization of inorganic carbon in the marine diatom Phaeodactylum tricornutum was investigated by the pH drift experiment, measurement of K_1/2 values of dissolved inorganic carbon (DIC) with pH change, and comparison of the rate of photosynthesis with the rate of the theoretical CO₂ formation from uncatalyzed HCO₃^– conversion in the medium. The higher pH compensation point (10.3) and insensitivity of the photosynthetic rate to acetazolamide indicate that the alga has good capacity for direct HCO₃^– utilization. The photosynthetic rate reached 150 times the theoretical CO₂ supply rate at 100 µmol L^–1 DIC (pH 9.0) in the presence of 10 mmol L^–1 K⁺ and 46 times that in the absence of K⁺, indicating that for pH 9.4-grown P. tricornutum, HCO₃^– in the medium is taken up through K⁺-dependent and -independent HCO₃^– transporters. The K_1/2 (CO₂) values at pH 8.2 were about 4 times higher than those at pH 9.0, whereas the K_1/2 (HCO₃^–) values at pH 8.2 were slightly lower than those at pH 9.0 whether without or with K⁺, providing further evidence for the presence of the two HCO₃^– transport patterns in this alga. Photosynthetic rate and affinity for HCO₃^– in the presence of K⁺, respectively, were about 2- and 7-fold higher than those in the absence of K⁺, indicating that K⁺-dependent HCO₃^– transport is a predominant pattern of HCO₃^– cellular uptake in low DIC concentration. However, as P. tricornutum was cultured at pH 7.2 or 8.0, photosynthetic affinities to HCO₃^– were not affected by K⁺, implying that K⁺-dependent HCO₃^– transport is induced when P. tricornutum is cultured at high alkaline pH.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Xiongwen Chen (xiongwenchen{at}eyou.com).

Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.106.079616.

^* Corresponding author; e-mail xiongwenchen{at}eyou.com; fax 86–0714–6515772.

Received February 23, 2006; returned for revision April 1, 2006; accepted April 2, 2006.