Journal
PLANTA
Volume 234, Issue 4, Pages 829-843Publisher
SPRINGER
DOI: 10.1007/s00425-011-1431-y
Keywords
Chlorella variabilis NC64A; Chlamydomonas reinhardtii; F-cluster domain; [FeFe]-hydrogenase; HYDA; Trebouxiophyceae
Categories
Funding
- United States Air Force Office of Scientific Research [FA9550-05-1-0365]
- National Aeronautics and Space Administration Graduate Research Program (GSRP) [NNG05GL52H]
- Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U. S. Department of Energy [DE-FG02-96ER20225]
- National Aeronautics and Space Administration Astrobiology Institute [NNA08C-N85A]
- National Aeronautics and Space Administration Astrobiology Institute
- United States Department of Energy Joint Genome Institute
- Office of Science of the United States Department of Energy [DE-AC02-05CH11231]
- U.S. Department of Energy (DOE) [DE-FG02-96ER20225] Funding Source: U.S. Department of Energy (DOE)
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[FeFe]-hydrogenases (HYDA) link the production of molecular H-2 to anaerobic metabolism in many green algae. Similar to Chlamydomonas reinhardtii, Chlorella variabilis NC64A (Trebouxiophyceae, Chlorophyta) exhibits [FeFe]-hydrogenase (HYDA) activity during anoxia. In contrast to C. reinhardtii and other chlorophycean algae, which contain hydrogenases with only the HYDA active site (H-cluster), C. variabilis NC64A is the only known green alga containing HYDA genes encoding accessory FeS cluster-binding domains (F-cluster). cDNA sequencing confirmed the presence of F-cluster HYDA1 mRNA transcripts, and identified deviations from the in silico splicing models. We show that HYDA activity in C. variabilis NC64A is coupled to anoxic photosynthetic electron transport (PSII linked, as well as PSII-independent) and dark fermentation. We also show that the in vivo H-2-photoproduction activity observed is as O-2 sensitive as in C. reinhardtii. The two C. variabilis NC64A HYDA sequences are similar to homologs found in more deeply branching bacteria (Thermotogales), diatoms, and heterotrophic flagellates, suggesting that an F-cluster HYDA is the ancestral enzyme in algae. Phylogenetic analysis indicates that the algal HYDA H-cluster domains are monophyletic, suggesting that they share a common origin, and evolved from a single ancestral F-cluster HYDA. Furthermore, phylogenetic reconstruction indicates that the multiple algal HYDA paralogs are the result of gene duplication events that occurred independently within each algal lineage. Collectively, comparative genomic, physiological, and phylogenetic analyses of the C. variabilis NC64A hydrogenase has provided new insights into the molecular evolution and diversity of algal [FeFe]-hydrogenases.
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