title: Characterization of five subgroups of the sieve element occlusion gene family in Glycine max reveals genes encoding non-forisome P-proteins, forisomes and forisome tails.
abstract: P-proteins are structural phloem proteins discussed to be involved in the rapid sealing of injured sieve elements. P-proteins are found in all dicotyledonous and some monocotyledonous plants, but additional crystalloid P-proteins, known as forisomes, have evolved solely in the Fabaceae. Both types are encoded by members of the sieve element occlusion (SEO) gene family, which comprises seven phylogenetic subgroups. The Fabaceae-specific subgroup 1 contains genes encoding forisome subunits in e.g. Medicago truncatula, Vicia faba, Dipteryx panamensis and Canavalia gladiata whereas basal subgroup 5 encodes P-proteins in Nicotiana tabacum (tobacco) and Arabidopsis thaliana. The function of remaining subgroups is still unknown. We chose Glycine max (soybean) as a model to investigate SEO proteins representing different subgroups in one species. We isolated native P-proteins to determine the SEO protein composition and analyzed the expression pattern, localization and structure of the G. max SEO proteins representing five of the subgroups. We found that subgroup 1 GmSEO genes encode forisome subunits, a member of subgroup 5 encodes a non-forisome P-protein and subgroup 2 GmSEO genes encode the components of forisome tails, which are present in a restricted selection of Fabaceaen species. We therefore present the first molecular characterization of a Fabaceae non-forisome P-protein and the first evidence that forisome tails are encoded by a phylogenetically-distinct branch of the SEO gene family.
authors.affiliation: Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Schlossplatz 8, 48143, Münster, Germany.
authors.forename: Sascia
authors.initials: S
authors.lastname: Zielonka
authors.forename: Antonia M
authors.initials: AM
authors.lastname: Ernst
authors.forename: Susan
authors.initials: S
authors.lastname: Hawat
authors.forename: Richard M
authors.initials: RM
authors.lastname: Twyman
authors.forename: Dirk
authors.initials: D
authors.lastname: Prüfer
authors.forename: Gundula A
authors.initials: GA
authors.lastname: Noll
mesh_terms: D005810:Multigene Family; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D030821:Plants, Genetically Modified / Q000378:metabolism; D021381:Protein Transport; D013025:Glycine max / Q000235:genetics* / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics
chemical_list: D010940:Plant Proteins