Ice‐binding proteins from the fungus Antarctomyces psychrotrophicus possibly originate from two different bacteria through horizontal gene transfer

• Published in: The FEBS Journal
• Main Authors: Arai, Tatsuya, Fukami, Daichi, Hoshino, Tamotsu, Kondo, Hidemasa, Tsuda, Sakae
• Other Authors: Japan Society for the Promotion of Science
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2018
• Subjects: Antarc*; Antarctica
• Online Access: http://dx.doi.org/10.1111/febs.14725; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Ffebs.14725; https://onlinelibrary.wiley.com/doi/pdf/10.1111/febs.14725; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/febs.14725; https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/febs.14725

Various microbes, including fungi and bacteria, that live in cold environments produce ice‐binding proteins ( IBP s) that protect them from freezing. Ascomycota and Basidiomycota are two major phyla of fungi, and Antarctomyces psychrotrophicus is currently designated as the sole ascomycete that produces IBP (Anp IBP ). However, its complete amino acid sequence, ice‐binding property, and evolutionary history have not yet been clarified. Here, we determined the peptide sequences of three new Anp IBP isoforms by total cDNA analysis and compared them with those of other microbial IBP s. The Anp IBP isoforms and ascomycete‐putative IBP s were found to be phylogenetically close to the bacterial ones but far from the basidiomycete ones, which is supported by the higher sequence identities to bacterial IBP s than basidiomycete IBP s, although ascomycetes are phylogenetically distant from bacteria. In addition, two of the isoforms of Anp IBP share low sequence identity and are not close in the phylogenetic tree. It is hence presumable that these two Anp IBP isoforms were independently acquired from different bacteria through horizontal gene transfer ( HGT ), which implies that ascomycetes and bacteria frequently exchange their IBP genes. The non‐colligative freezing‐point depression ability of Anp IBP was not very high, whereas it exhibited significant abilities of ice recrystallization inhibition, ice shaping, and cryo‐protection against freeze–thaw cycles even at submicromolar concentrations. These results suggest that HGT is crucial for the cold‐adaptive evolution of ascomycetes, and their IBP s offer freeze resistance to organisms to enable them to inhabit the icy environments of Antarctica. Databases Nucleotide sequence data are available in the DDBJ database under the accession numbers LC378707 , LC378707 , LC378707 for Anp IBP 1a, Anp IBP 1b, Anp IBP 2, respectively.