title: Analysis of Porphyra membrane transporters demonstrates gene transfer among photosynthetic eukaryotes and numerous sodium-coupled transport systems.
abstract: Membrane transporters play a central role in many cellular processes that rely on the movement of ions and organic molecules between the environment and the cell, and between cellular compartments. Transporters have been well characterized in plants and green algae, but little is known about transporters or their evolutionary histories in the red algae. Here we examined 482 expressed sequence tag contigs that encode putative membrane transporters in the economically important red seaweed Porphyra (Bangiophyceae, Rhodophyta). These contigs are part of a comprehensive transcriptome dataset from Porphyra umbilicalis and Porphyra purpurea. Using phylogenomics, we identified 30 trees that support the expected monophyly of red and green algae/plants (i.e. the Plantae hypothesis) and 19 expressed sequence tag contigs that show evidence of endosymbiotic/horizontal gene transfer involving stramenopiles. The majority (77%) of analyzed contigs encode transporters with unresolved phylogenies, demonstrating the difficulty in resolving the evolutionary history of genes. We observed molecular features of many sodium-coupled transport systems in marine algae, and the potential for coregulation of Porphyra transporter genes that are associated with fatty acid biosynthesis and intracellular lipid trafficking. Although both the tissue-specific and subcellular locations of the encoded proteins require further investigation, our study provides red algal gene candidates associated with transport functions and novel insights into the biology and evolution of these transporters.
authors.affiliation: Department of Ecology, Evolution and Natural Resources, and Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, New Jersey 08901, USA.
authors.forename: Cheong Xin
authors.initials: CX
authors.lastname: Chan
authors.forename: Simone
authors.initials: S
authors.lastname: Zäuner
authors.forename: Glen
authors.initials: G
authors.lastname: Wheeler
authors.forename: Arthur R
authors.initials: AR
authors.lastname: Grossman
authors.forename: Simon E
authors.initials: SE
authors.lastname: Prochnik
authors.forename: Nicolas A
authors.initials: NA
authors.lastname: Blouin
authors.forename: Yunyun
authors.initials: Y
authors.lastname: Zhuang
authors.forename: Christoph
authors.initials: C
authors.lastname: Benning
authors.forename: Gry Mine
authors.initials: GM
authors.lastname: Berg
authors.forename: Charles
authors.initials: C
authors.lastname: Yarish
authors.forename: Renée L
authors.initials: RL
authors.lastname: Eriksen
authors.forename: Anita S
authors.initials: AS
authors.lastname: Klein
authors.forename: Senjie
authors.initials: S
authors.lastname: Lin
authors.forename: Ira
authors.initials: I
authors.lastname: Levine
authors.forename: Susan H
authors.initials: SH
authors.lastname: Brawley
authors.forename: Debashish
authors.initials: D
authors.lastname: Bhattacharya
mesh_terms: D020346:Aquaporins / Q000378:metabolism; D001692:Biological Transport / Q000235:genetics; D020013:Calcium Signaling / Q000235:genetics; D056890:Eukaryota / Q000235:genetics*; D019143:Evolution, Molecular; D020224:Expressed Sequence Tags; D005618:Fresh Water; D022761:Gene Transfer, Horizontal / Q000235:genetics*; D005796:Genes; D017136:Ion Transport / Q000235:genetics; D050356:Lipid Metabolism / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009566:Nitrates / Q000378:metabolism; D010788:Photosynthesis / Q000235:genetics*; D010802:Phylogeny; D044664:Porphyra / Q000235:genetics*; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D012623:Seawater; D012964:Sodium / Q000378:metabolism*; D059467:Transcriptome / Q000235:genetics
chemical_list: D020346:Aquaporins; D026901:Membrane Transport Proteins; D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D012964:Sodium