title: Acclimation of Antarctic Chlamydomonas to the sea-ice environment: a transcriptomic analysis.
abstract: The Antarctic green alga Chlamydomonas sp. ICE-L was isolated from sea ice. As a psychrophilic microalga, it can tolerate the environmental stress in the sea-ice brine, such as freezing temperature and high salinity. We performed a transcriptome analysis to identify freezing stress responding genes and explore the extreme environmental acclimation-related strategies. Here, we show that many genes in ICE-L transcriptome that encoding PUFA synthesis enzymes, molecular chaperon proteins, and cell membrane transport proteins have high similarity to the gens from Antarctic bacteria. These ICE-L genes are supposed to be acquired through horizontal gene transfer from its symbiotic microbes in the sea-ice brine. The presence of these genes in both sea-ice microalgae and bacteria indicated the biological processes they involved in are possibly contributing to ICE-L success in sea ice. In addition, the biological pathways were compared between ICE-L and its closely related sister species, Chlamydomonas reinhardtii and Volvox carteri. In ICE-L transcripome, many sequences homologous to the plant or bacteria proteins in the post-transcriptional, post-translational modification, and signal-transduction KEGG pathways, are absent in the nonpsychrophilic green algae. These complex structural components might imply enhanced stress adaptation capacity. At last, differential gene expression analysis at the transcriptome level of ICE-L indicated that genes that associated with post-translational modification, lipid metabolism, and nitrogen metabolism are responding to the freezing treatment. In conclusion, the transcriptome of Chlamydomonas sp. ICE-L is very useful for exploring the mutualistic interaction between microalgae and bacteria in sea ice; and discovering the specific genes and metabolism pathways responding to the freezing acclimation in psychrophilic microalgae.
authors.affiliation: Key Laboratory of Marine Bioactive Substances, First Institute of Oceanography, State Oceanic Administration, Xianxialing Road 6th, Qingdao, 266061, China. ch.lliu@163.com.|Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266000, China. ch.lliu@163.com.
authors.forename: Chenlin
authors.initials: C
authors.lastname: Liu
authors.affiliation: Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266000, China.|Key Lab of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China.
authors.forename: Xiuliang
authors.initials: X
authors.lastname: Wang
authors.affiliation: Key Laboratory of Marine Bioactive Substances, First Institute of Oceanography, State Oceanic Administration, Xianxialing Road 6th, Qingdao, 266061, China.
authors.forename: Xingna
authors.initials: X
authors.lastname: Wang
authors.affiliation: Key Laboratory of Marine Bioactive Substances, First Institute of Oceanography, State Oceanic Administration, Xianxialing Road 6th, Qingdao, 266061, China.
authors.forename: Chengjun
authors.initials: C
authors.lastname: Sun
mesh_terms: D000064:Acclimatization / Q000235:genetics*; D000864:Antarctic Regions; D002696:Chlamydomonas / Q000235:genetics* / Q000378:metabolism; D003080:Cold Temperature; D022761:Gene Transfer, Horizontal; D046448:Ice Cover; D050356:Lipid Metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D012623:Seawater; D015398:Signal Transduction / Q000235:genetics; D059467:Transcriptome
chemical_list: D026901:Membrane Transport Proteins; D018832:Molecular Chaperones; D010940:Plant Proteins
keywords: Antarctic sea ice; Freezing acclimation; Horizontal gene transfer; Psychrophilic green microalga; Transcriptomic analysis