First published online April 22, 2005; 10.1104/pp.104.058982
Plant Physiology 138:207-217 (2005)
© 2005 American Society of Plant Biologists
BIOENERGETICS AND PHOTOSYNTHESIS
Localization of Soluble -Carbonic Anhydrase in the Marine Diatom Phaeodactylum tricornutum. Sorting to the Chloroplast and Cluster Formation on the Girdle Lamellae1,[w]
Yuji Tanaka2,
Daisuke Nakatsuma2,
Hisashi Harada,
Maki Ishida and
Yusuke Matsuda*
Department of Bioscience, School of Science and Technology, Kwansei-Gakuin University, Sanda 6691337 Hyogo, Japan
A -carbonic anhydrase (CA) in the marine diatom Phaeodactylum tricornutum (PtCA1) is encoded by the nuclear genome. This enzyme was previously found to be important for the operation of photosynthesis with a high affinity for dissolved inorganic carbon. A cDNA sequence that encodes PtCA1 (ptca1) was shown to possess a presequence of 138 bp (pre138), which encodes an N-terminal sequence of 46 amino acids (Pre46AA) that does not exist in the mature PtCA1. In this study, pre138 was ligated with the enhanced green fluorescent protein (GFP) gene (egfp), and introduced into P. tricornutum by microprojectile bombardment. Subsequently, the expressed Pre46AA-GFP fusion was shown to be localized in the chloroplast stroma, whereas the expressed GFP without Pre46AA was localized in the cytoplasm. Insertion of the DNA sequence, encoding a mature region of ptca1 (mptca1) between pre138 and egfp, resulted in the formation of particles with concentrated GFP fluorescence in the stroma of P. tricornutum. These particles, 0.3 to 3.0 µm in size, were shown to be distinct from the mitochondria and localized on the surface of the putative girdle lamella. The attachment of the initial one-half of the pre138 to the mptca1-egfp fusion caused the expressed GFP fusion to accumulate in areas surrounding the chloroplast, presumably due to the presence of the endoplasmic reticulum signal encoded by the initial half-sequence and to the absence of the chloroplast transit sequence. These results indicate that PtCA1 is targeted to the stroma by the bipartite sequences of Pre46AA and that the observed GFP particles are formed specifically in the stroma due to the function of the mptca1.
1 This work was supported in part by the Showa-Shell-Sekiyu Environmental Research Foundation (to Y.M.), by the Kato Memorial Bioscience Foundation (to Y.M.), and by the University-Industry Joint Research Project of the Ministry of Education, Culture, Sports, Science and Technology.
2 These authors contributed equally to the paper.
[w] The online version of this article contains Web-only data.
Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.058982.
* Corresponding author; e-mail yusuke{at}ksc.kwansei.ac.jp; fax 81795658542.
Received January 4, 2005;
returned for revision February 20, 2005;
accepted February 21, 2005.
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