title: Identification and characterization of genes encoding two novel LEA proteins in Antarctic and temperate strains of Chlorella vulgaris.
abstract: An Antarctic strain (NJ-7) of Chlorella vulgaris possesses the same 18S rRNA sequence as that of a temperate strain (UTEX259), but shows significantly higher freezing tolerance than the latter. Suppression subtractive hybridization (SSH) was performed to identify genes of intensified expression in NJ-7 relative to UTEX259. Among the genes identified, Ccor1 and Ccor2, co-organized in the same gene cluster Ccor1-Ccor2-Ccor1-Ccor2, showed much higher expression levels in NJ-7 than in UTEX259 at both 20°C and 4°C. As detected by Northern blot and Western blot analyses, the two genes were cold-inducible in NJ-7 but almost not expressed in UTEX259. Their encoded products are predicted to share 55.7% identity to each other and possess physicochemical characteristics similar to that of late embryogenesis abundant (LEA) proteins in plants. The purified recombinant Ccor1 and Ccor2 showed high heat-stability and could act as cryoprotectants to lactate dehydrogenase in vitro. Based on their expression patterns and protein characteristics, we propose that Ccor1 and Ccor2 are two novel LEA proteins and are related to the greatly enhanced freezing tolerance in the Antarctic strain.
authors.affiliation: State Key laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China.
authors.forename: Xiaoxiang
authors.initials: X
authors.lastname: Liu
authors.forename: Yali
authors.initials: Y
authors.lastname: Wang
authors.forename: Hong
authors.initials: H
authors.lastname: Gao
authors.forename: Xudong
authors.initials: X
authors.lastname: Xu
mesh_terms: D000864:Antarctic Regions; D015139:Blotting, Southern; D048408:Chlorella vulgaris / Q000235:genetics*; D003451:Cryoprotective Agents / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics*; D006358:Hot Temperature; D057927:Hydrophobic and Hydrophilic Interactions; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D055550:Protein Stability; D011994:Recombinant Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D003451:Cryoprotective Agents; D010940:Plant Proteins; D011994:Recombinant Proteins; C066246:late embryogenesis abundant protein, plant; D007770:L-Lactate Dehydrogenase