title: The Origin and Evolution of the Plant Cell Surface: Algal Integrin-Associated Proteins and a New Family of Integrin-Like Cytoskeleton-ECM Linker Proteins.
abstract: The extracellular matrix of scaly green flagellates consists of small organic scales consisting of polysaccharides and scale-associated proteins (SAPs). Molecular phylogenies have shown that these organisms represent the ancestral stock of flagellates from which all green plants (Viridiplantae) evolved. The molecular characterization of four different SAPs is presented. Three SAPs are type-2 membrane proteins with an arginine/alanine-rich short cytoplasmic tail and an extracellular domain that is most likely of bacterial origin. The fourth protein is a filamin-like protein. In addition, we report the presence of proteins similar to the integrin-associated proteins α-actinin (in transcriptomes of glaucophytes and some viridiplants), LIM-domain proteins, and integrin-associated kinase in transcriptomes of viridiplants, glaucophytes, and rhodophytes. We propose that the membrane proteins identified are the predicted linkers between scales and the cytoskeleton. These proteins are present in many green algae but are apparently absent from embryophytes. These proteins represent a new protein family we have termed gralins for green algal integrins. Gralins are absent from embryophytes. A model for the evolution of the cell surface proteins in Plantae is discussed.
authors.affiliation: Biozentrum Köln, Botanical Institute, Universität zu Köln, Germany b.becker@uni-koeln.de.
authors.forename: Burkhard
authors.initials: B
authors.lastname: Becker
authors.affiliation: Biozentrum Köln, Botanical Institute, Universität zu Köln, Germany.
authors.forename: Jean Michel
authors.initials: JM
authors.lastname: Doan
authors.affiliation: Biozentrum Köln, Botanical Institute, Universität zu Köln, Germany.
authors.forename: Brandon
authors.initials: B
authors.lastname: Wustman
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Carpenter
authors.affiliation: BGI-Shenzhen, Bei Shan Industrial Zone, Shenzhen, China.
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.affiliation: BGI-Shenzhen, Bei Shan Industrial Zone, Shenzhen, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada BGI-Shenzhen, Bei Shan Industrial Zone, Shenzhen, China Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Gane K-S
authors.initials: GK
authors.lastname: Wong
authors.affiliation: Biozentrum Köln, Botanical Institute, Universität zu Köln, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Melkonian
mesh_terms: D020418:Algal Proteins / Q000032:analysis / Q000737:chemistry* / Q000235:genetics; D000460:Chlorophyta / Q000235:genetics / Q000648:ultrastructure; D003198:Computer Simulation; D019143:Evolution, Molecular; D008562:Membrane Glycoproteins / Q000032:analysis / Q000737:chemistry* / Q000235:genetics; D008840:Microfilament Proteins / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
chemical_list: D020418:Algal Proteins; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; D010940:Plant Proteins
keywords: Glaucophyta; Rhodophyta; Viridiplantae; actinin; filamin; gralin