title: Diversity of the superfamily of phloem lectins (phloem protein 2) in angiosperms.
abstract: Phloem protein 2 (PP2) is one of the most abundant and enigmatic proteins in the phloem sap. Although thought to be associated with structural P-protein, PP2 is translocated in the assimilate stream where its lectin activity or RNA-binding properties can exert effects over long distances. Analyzing the diversity of these proteins in vascular plants led to the identification of PP2-like genes in species from 17 angiosperm and gymnosperm genera. This wide distribution of PP2 genes in the plant kingdom indicates that they are ancient and common in vascular plants. Their presence in cereals and gymnosperms, both of which lack structural P-protein, also supports a wider role for these proteins. Within this superfamily, PP2 proteins have considerable size polymorphism. This is attributable to variability in the length of the amino terminus that extends from a highly conserved domain. The conserved PP2 domain was identified in the proteins encoded by six genes from several cucurbits, celery (Apium graveolens), and Arabidopsis that are specifically expressed in the sieve element-companion cell complex. The acquisition of additional modular domains in the amino-terminal extensions of other PP2-like proteins could reflect divergence from its phloem function.
authors.affiliation: Laboratoire de Biologie Cellulaire, Institut National de la Recherche Agronomique, Versailles 78026, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Dinant
authors.forename: Anna M
authors.initials: AM
authors.lastname: Clark
authors.forename: Yanmin
authors.initials: Y
authors.lastname: Zhu
authors.forename: Françoise
authors.initials: F
authors.lastname: Vilaine
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Palauqui
authors.forename: Chantal
authors.initials: C
authors.lastname: Kusiak
authors.forename: Gary A
authors.initials: GA
authors.lastname: Thompson
mesh_terms: D000595:Amino Acid Sequence; D000077102:Apium / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D017124:Conserved Sequence / Q000235:genetics; D028462:Cucumis / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D019684:Magnoliopsida / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D010802:Phylogeny; D037121:Plant Lectins / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D037121:Plant Lectins; C091028:phloem lectin