title: Algae sense exact temperatures: small heat shock proteins are expressed at the survival threshold temperature in Cyanidioschyzon merolae and Chlamydomonas reinhardtii.
abstract: The primitive red alga Cyanidioschyzon merolae inhabits acidic hot springs and shows robust resistance to heat shock treatments up to 63 °C. Microarray analysis was performed to identify the key genes underlying the high temperature tolerance of this organism. Among the upregulated genes that were identified, we focused on two small heat shock proteins (sHSPs) that belong to a unique class of HSP families. These two genes are located side by side in an inverted repeat orientation on the same chromosome and share a promoter. These two genes were simultaneously and rapidly upregulated in response to heat shock treatment (>1,000-fold more than the control). Interestingly, upregulation appeared to be triggered not by a difference in temperatures, but rather by the absolute temperature. Similar sHSP structural genes have been reported in the green alga Chlamydomonas reinhardtii, but the threshold temperature for the expression of these sHSP-encoding genes in Ch. reinhardtii was different from the threshold temperature for the expression of the sHSP genes from Cy. merolae. These results indicate the possible importance of an absolute temperature sensing system in the evolution and tolerance of high-temperature conditions among unicellular microalgae.
authors.affiliation: Laboratory of Plant Molecular Genetics, Department of Botany, Kyoto University, Oiwake-cho, Kita-Shirakawa, Kyoto, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kobayashi
authors.affiliation: Laboratory of Plant Molecular Genetics, Department of Botany, Kyoto University, Oiwake-cho, Kita-Shirakawa, Kyoto, Japan.
authors.forename: Naomi
authors.initials: N
authors.lastname: Harada
authors.affiliation: Laboratory of Plant Molecular Genetics, Department of Botany, Kyoto University, Oiwake-cho, Kita-Shirakawa, Kyoto, Japan.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Nishimura
authors.affiliation: Department of Biological Science and Chemistry, Faculty of Science, Graduate School of Medicine, Yamaguchi University, Yamaguchi, Japan.
authors.forename: Takafumi
authors.initials: T
authors.lastname: Saito
authors.affiliation: Symbiosis and Cell Evolution Laboratory, Center for Frontier Research, National Institute of Genetics, Mishima, Shizuoka, Japan.
authors.forename: Mami
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Symbiosis and Cell Evolution Laboratory, Center for Frontier Research, National Institute of Genetics, Mishima, Shizuoka, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Fujiwara
authors.affiliation: Faculty of Science, Rikkyo University, Toshima-ku, Tokyo, Japan Core Research for Evolutional Science and Technology (CREST, JST), Japan Science and Technology Agency, Kawaguchi, Japan.
authors.forename: Tsuneyoshi
authors.initials: T
authors.lastname: Kuroiwa
authors.affiliation: Department of Biological Science and Chemistry, Faculty of Science, Graduate School of Medicine, Yamaguchi University, Yamaguchi, Japan Core Research for Evolutional Science and Technology (CREST, JST), Japan Science and Technology Agency, Kawaguchi, Japan misumi@yamaguchi-u.ac.jp.
authors.forename: Osami
authors.initials: O
authors.lastname: Misumi
mesh_terms: D000595:Amino Acid Sequence; D002696:Chlamydomonas / Q000378:metabolism*; D016825:Chlamydomonas reinhardtii / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D050888:Heat-Shock Proteins, Small / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000145:classification / Q000378:metabolism*; D013696:Temperature
chemical_list: D050888:Heat-Shock Proteins, Small; D010940:Plant Proteins
keywords: HSP; environmental adaptation; heat resistance; microarray; unicellular algae