title: Plant expansins are a complex multigene family with an ancient evolutionary origin.
abstract: Expansins are a group of extracellular proteins that directly modify the mechanical properties of plant cell walls, leading to turgor-driven cell extension. Within the completely sequenced Arabidopsis genome, we identified 38 expansin sequences that fall into three discrete subfamilies. Based on phylogenetic analysis and shared intron patterns, we propose a new, systematic nomenclature of Arabidopsis expansins. Further phylogenetic analysis, including expansin sequences found here in monocots, pine (Pinus radiata, Pinus taeda), fern (Regnellidium diphyllum, Marsilea quadrifolia), and moss (Physcomitrella patens) indicate that the three plant expansin subfamilies arose and began diversifying very early in, if not before, colonization of land by plants. Closely related "expansin-like" sequences were also identified in the social amoeba, Dictyostelium discoidium, suggesting that these wall-modifying proteins have a very deep evolutionary origin.
authors.affiliation: Department of Biology, University of York, York YO10 5YW, United Kingdom.
authors.forename: Yi
authors.initials: Y
authors.lastname: Li
authors.forename: Catherine P
authors.initials: CP
authors.lastname: Darley
authors.forename: Verónica
authors.initials: V
authors.lastname: Ongaro
authors.forename: Andrew
authors.initials: A
authors.lastname: Fleming
authors.forename: Ori
authors.initials: O
authors.lastname: Schipper
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Baldauf
authors.forename: Simon J
authors.initials: SJ
authors.lastname: McQueen-Mason
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D019068:Bryopsida / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D004023:Dictyostelium / Q000235:genetics; D019143:Evolution, Molecular; D029624:Ferns / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D010802:Phylogeny; D028223:Pinus / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D010944:Plants / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D021382:Protein Sorting Signals / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D010940:Plant Proteins; D021382:Protein Sorting Signals; C095825:expansin protein, plant