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First published online February 16, 2007; 10.1104/pp.106.092536 Plant Physiology 143:1802-1816 (2007) © 2007 American Society of Plant Biologists OPEN ACCESS ARTICLE
Tracing the Evolution of the Light-Harvesting Antennae in Chlorophyll a/b-Containing Organisms1,[OA]Department of Biology, University of New Brunswick, Fredericton, New Brunswick, Canada E3B 5A3 (A.G.K., D.G.D.); Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J1 (T.B., R.W.L.); Institute of Biological Sciences, University of Tsukuba, Tsukaba, Ibaraki 3058572, Japan (K.-I.I.); and Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4 (P.K.)
The light-harvesting complexes (LHCs) of land plants and green algae have essential roles in light capture and photoprotection. Though the functional diversity of the individual LHC proteins are well described in many land plants, the extent of this family in the majority of green algal groups is unknown. To examine the evolution of the chlorophyll a/b antennae system and to infer its ancestral state, we initiated several expressed sequence tag projects from a taxonomically broad range of chlorophyll a/b-containing protists. This included representatives from the Ulvophyceae (Acetabularia acetabulum), the Mesostigmatophyceae (Mesostigma viride), and the Prasinophyceae (Micromonas sp.), as well as one representative from each of the Euglenozoa (Euglena gracilis) and Chlorarachniophyta (Bigelowiella natans), whose plastids evolved secondarily from a green alga. It is clear that the core antenna system was well developed prior to green algal diversification and likely consisted of the CP29 (Lhcb4) and CP26 (Lhcb5) proteins associated with photosystem II plus a photosystem I antenna composed of proteins encoded by at least Lhca3 and two green algal-specific proteins encoded by the Lhca2 and 9 genes. In organisms containing secondary plastids, we found no evidence for orthologs to the plant/algal antennae with the exception of CP29. We also identified PsbS homologs in the Ulvophyceae and the Prasinophyceae, indicating that this distinctive protein appeared prior to green algal diversification. This analysis provides a snapshot of the antenna systems in diverse green algae, and allows us to infer the changing complexity of the antenna system during green algal evolution.
1 This work was supported by grants from Genome Canada, Genome Atlantic, and Genome British Columbia as part of the Protist EST Program and supported through the Natural Science and Engineering Research Council of Canada. 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: Dion G. Durnford (durnford{at}unb.ca). [OA] Open Access articles can be viewed online without a subscription. www.plantphysiol.org/cgi/doi/10.1104/pp.106.092536 * Corresponding author; e-mail durnford{at}unb.ca; fax 5064533583. Received November 2, 2006; accepted February 7, 2007; published February 16, 2007. This article has been cited by other articles:
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