Phylogenetic analysis of the light-harvesting system in Chromera velia
Chromera velia is a newly discovered photosynthetic eukaryotic alga that has functional chloroplasts closely related to the apicoplast of apicomplexan parasites. Recently, the chloroplast in C. velia was shown to be derived from the red algal lineage. Light-harvesting protein complexes (LHC), which are a group of proteins involved in photon capture and energy transfer in photosynthesis, are important for photosynthesis efficiency, photo-adaptation/accumulation and photo-protection. Although these proteins are encoded by genes located in the nucleus, LHC peptides migrate and function in the chloroplast, hence the LHC may have a different evolutionary history compared to chloroplast evolution. Here, we compare the phylogenetic relationship of the C. velia LHCs to LHCs from other photosynthetic organisms. Twenty-three LHC homologues retrieved from C. velia EST sequences were aligned according to their conserved regions. The C. velia LHCs are positioned in four separate groups on trees constructed by neighbour-joining, maximum likelihood and Bayesian methods. A major group of seventeen LHCs from C. velia formed a separate cluster that was closest to dinoflagellate LHC, and to LHC and fucoxanthin chlorophyll-binding proteins from diatoms. One C. velia LHC sequence grouped with LI1818/LI818-like proteins, which were recently identified as environmental stress-induced protein complexes. Only three LHC homologues from C. velia grouped with the LHCs from red algae.
KeywordsLight-harvesting protein complexes (LHC) Chromera velia (C. velia) Membrane-spanning regions Chlorophyll-binding protein complexes
Fucoxanthin chlorophyll-binding protein
Light-harvesting protein complexes
Light-harvesting complexes bound to photosystem I
Light-harvesting complexes bound to photosystem II
Magnesium divinyl pheoporphyrin a5 monomethyl ester
M.C. holds an Australian Research Council Queen Elizabeth II Fellowship and thanks the Australian Research Council for support. This work was partially supported by Australian Research Council Discovery Project DP0986372 to D.C. and J.Š. H.P. would like to thank Dr. P. Loughlin, Mr. Y. Lin and Ms. Y. Li for helpful discussions. M.C. thanks Dr. Roger Hiller for reading the manuscript.
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