title: Arabinogalactan proteins have deep roots in eukaryotes: identification of genes and epitopes in brown algae and their role in Fucus serratus embryo development.
abstract: Arabinogalactan proteins (AGPs) are highly glycosylated, hydroxyproline-rich proteins found at the cell surface of plants, where they play key roles in developmental processes. Brown algae are marine, multicellular, photosynthetic eukaryotes. They belong to the phylum Stramenopiles, which is unrelated to land plants and green algae (Chloroplastida). Brown algae share common evolutionary features with other multicellular organisms, including a carbohydrate-rich cell wall. They differ markedly from plants in their cell wall composition, and AGPs have not been reported in brown algae. Here we investigated the presence of chimeric AGP-like core proteins in this lineage. We report that the genome sequence of the brown algal model Ectocarpus siliculosus encodes AGP protein backbone motifs, in a gene context that differs considerably from what is known in land plants. We showed the occurrence of AGP glycan epitopes in a range of brown algal cell wall extracts. We demonstrated that these chimeric AGP-like core proteins are developmentally regulated in embryos of the order Fucales and showed that AGP loss of function seriously impairs the course of early embryogenesis. Our findings shine a new light on the role of AGPs in cell wall sensing and raise questions about the origin and evolution of AGPs in eukaryotes.
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR 8227, Station Biologique de Roscoff, Integrative Biology of Marine Models, CS 90074, F-29688 Roscoff, France.|CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688 Roscoff, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Hervé
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR 8227, Station Biologique de Roscoff, Integrative Biology of Marine Models, CS 90074, F-29688 Roscoff, France.|CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688 Roscoff, France.
authors.forename: Amandine
authors.initials: A
authors.lastname: Siméon
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR 8227, Station Biologique de Roscoff, Integrative Biology of Marine Models, CS 90074, F-29688 Roscoff, France.|CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688 Roscoff, France.
authors.forename: Murielle
authors.initials: M
authors.lastname: Jam
authors.affiliation: ARC Centre of Excellence in Plant Cell Walls, School of BioSciences, University of Melbourne, Melbourne, Vic, Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: Cassin
authors.affiliation: ARC Centre of Excellence in Plant Cell Walls, School of BioSciences, University of Melbourne, Melbourne, Vic, Australia.
authors.forename: Kim L
authors.initials: KL
authors.lastname: Johnson
authors.affiliation: Department of Plant and Environmental Sciences, Faculty of Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Armando A
authors.initials: AA
authors.lastname: Salmeán
authors.affiliation: Department of Plant and Environmental Sciences, Faculty of Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: William G T
authors.initials: WG
authors.lastname: Willats
authors.affiliation: ARC Centre of Excellence in Plant Cell Walls, School of BioSciences, University of Melbourne, Melbourne, Vic, Australia.
authors.forename: Monika S
authors.initials: MS
authors.lastname: Doblin
authors.affiliation: ARC Centre of Excellence in Plant Cell Walls, School of BioSciences, University of Melbourne, Melbourne, Vic, Australia.
authors.forename: Antony
authors.initials: A
authors.lastname: Bacic
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR 8227, Station Biologique de Roscoff, Integrative Biology of Marine Models, CS 90074, F-29688 Roscoff, France.|CNRS, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688 Roscoff, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: Kloareg
mesh_terms: D000595:Amino Acid Sequence; D002455:Cell Division / Q000528:radiation effects; D002473:Cell Wall / Q000378:metabolism / Q000528:radiation effects; D000939:Epitopes / Q000378:metabolism*; D044645:Fucus / Q000235:genetics* / Q000254:growth & development* / Q000528:radiation effects; D017343:Genes, Plant; D016678:Genome; D007202:Indicators and Reagents; D008027:Light; D008954:Models, Biological; D009088:Mucoproteins / Q000737:chemistry / Q000378:metabolism*; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D000072417:Protein Domains; D012689:Sequence Homology, Nucleic Acid; D015053:Zygote / Q000378:metabolism
chemical_list: D000939:Epitopes; D007202:Indicators and Reagents; D009088:Mucoproteins; D010940:Plant Proteins; C006619:arabinogalactan proteins
keywords: Ectocarpus; Fucus embryo; arabinogalactan proteins (AGPs); brown algae; cell elongation; cell polarity; cell wall; cell wall evolution