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ENVIRONMENTAL STRESS AND ADAPTATION TO STRESS

Regulation of the Expression of Intracellular -Carbonic Anhydrase in Response to CO₂ and Light in the Marine Diatom Phaeodactylum tricornutum¹

Department of Bioscience, School of Science and Technology, Kwansei-Gakuin University, Sanda, Hyogo, Japan, 669–1337

Cells of the marine diatom Phaeodactylum tricornutum Bohlin (UTEX 642) grown in 5% CO₂ were transferred to air-level CO₂ in the light or dark and allowed to acclimate to air. No accumulation of the transcript of the P. tricornutum -carbonic anhydrase 1 (ptca1) was detected in 5% CO₂-grown cells, but ptca1 mRNA accumulated and reached a peak after 6 h acclimation to air but decreased over the next 18 h. A similar accumulation time course was observed in cells air-acclimated in the dark, except that levels of mRNA were <50% those in the light. These results suggest that air-level [CO₂] is required to trigger the transcription of ptca1 and that light affects the extent of acclimation. During acclimation to air for 120 h in the light, levels of ptca1 mRNA exhibited a periodic oscillation with a cycle of about 24 h, which, however, was not reflected in protein accumulation levels. A 5'-upstream region from the transcription-start site toward –1,292 bp of ptca1 was cloned by inverse polymerase chain reaction, and 5'-truncations were carried out on this fragment. The truncated promoter regions were fused with the -glucuronidase gene (uidA) and introduced into P. tricornutum. The promoter fragments, truncated at positions –1,292, –824, –484, –225, and –70 bp, conferred on transformants clear CO₂-responsive -glucuronidase expressions. In contrast, the CO₂-responsive regulation was severely impaired or completely abolished by truncations, respectively, at position –50 or –30 bp. These results indicate that critical cis-elements required for CO₂-responsive transcription of ptca1 may be located between –70 and –30 bp relative to the transcription start site.

Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.105.065185.

^* Corresponding author; e-mail yusuke{at}ksc.kwansei.ac.jp; fax 81–79–565–8542.

Received May 5, 2005; returned for revision July 9, 2005; accepted July 27, 2005.

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				H. Harada, K. Nakajima, K. Sakaue, and Y. Matsuda CO2 Sensing at Ocean Surface Mediated by cAMP in a Marine Diatom Plant Physiology, November 1, 2006; 142(3): 1318 - 1328. [Abstract] [Full Text] [PDF]