title: Is chloroplastic class IIA aldolase a marine enzyme?
abstract: Expressed sequence tag analyses revealed that two marine Chlorophyceae green algae, Chlamydomonas sp. W80 and Chlamydomonas sp. HS5, contain genes coding for chloroplastic class IIA aldolase (fructose-1, 6-bisphosphate aldolase: FBA). These genes show robust monophyly with those of the marine Prasinophyceae algae genera Micromonas, Ostreococcus and Bathycoccus, indicating that the acquisition of this gene through horizontal gene transfer by an ancestor of the green algal lineage occurred prior to the divergence of the core chlorophytes (Chlorophyceae and Trebouxiophyceae) and the prasinophytes. The absence of this gene in some freshwater chlorophytes, such as Chlamydomonas reinhardtii, Volvox carteri, Chlorella vulgaris, Chlorella variabilis and Coccomyxa subellipsoidea, can therefore be explained by the loss of this gene somewhere in the evolutionary process. Our survey on the distribution of this gene in genomic and transcriptome databases suggests that this gene occurs almost exclusively in marine algae, with a few exceptions, and as such, we propose that chloroplastic class IIA FBA is a marine environment-adapted enzyme. This hypothesis was also experimentally tested using Chlamydomonas W80, for which we found that the transcript levels of this gene to be significantly lower under low-salt (that is, simulated terrestrial) conditions. Expression analyses of transcriptome data for two algae, Prymnesium parvum and Emiliania huxleyi, taken from the Sequence Read Archive database also indicated that the expression of this gene under terrestrial conditions (low NaCl and low sulfate) is significantly downregulated. Thus, these experimental and transcriptome data provide support for our hypothesis.
authors.affiliation: Department of Applied Life Science, Sojo University, Kumamoto, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Miyasaka
authors.affiliation: Department of Applied Life Science, Sojo University, Kumamoto, Japan.
authors.forename: Takeru
authors.initials: T
authors.lastname: Ogata
authors.affiliation: The Kansai Electric Power Co., Environmental Research Center, Keihanna-Plaza, Kyoto, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: School of Environmental Science and Engineering, Kochi University of Technology, Kochi, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ohama
authors.affiliation: Chugai Technos Corporation, Hiroshima, Japan.
authors.forename: Sanae
authors.initials: S
authors.lastname: Kano
authors.affiliation: Chugai Technos Corporation, Hiroshima, Japan.
authors.forename: Fujiwara
authors.identifier: 0000-0003-1728-1630
authors.initials: F
authors.lastname: Kazuhiro
authors.affiliation: Department of Applied Life Science, Sojo University, Kumamoto, Japan.
authors.forename: Shuhei
authors.initials: S
authors.lastname: Hayashi
authors.affiliation: Department of Applied Life Science, Sojo University, Kumamoto, Japan.
authors.forename: Shinjiro
authors.initials: S
authors.lastname: Yamamoto
authors.affiliation: Graduate School of Horticulture, Faculty of Horticulture, Chiba University, Chiba, Japan.
authors.forename: Hiro
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: Environmental Biotechnology Laboratory, Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Matsuura
authors.affiliation: Environmental Biotechnology Laboratory, Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan.
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Hirata
mesh_terms: D005075:Biological Evolution; D000460:Chlorophyta / Q000145:classification / Q000201:enzymology* / Q000235:genetics; D002736:Chloroplasts / Q000201:enzymology* / Q000235:genetics; D005634:Fructose-Bisphosphate Aldolase / Q000235:genetics / Q000378:metabolism*; D022761:Gene Transfer, Horizontal; D016678:Genome; D023281:Genomics; D008969:Molecular Sequence Data; D010802:Phylogeny; D012623:Seawater / Q000737:chemistry
chemical_list: D005634:Fructose-Bisphosphate Aldolase