title: Arabinogalactan proteins mark stigmatic receptivity in the protogynous flowers of Magnolia virginiana (Magnoliaceae).
abstract: OBJECTIVE
  Factors affecting floral receptivity in angiosperms remain opaque, but recent studies suggest that the acquisition of stigmatic receptivity associated with cell-wall-related arabinogalactan proteins (AGPs) may be a widespread feature of flowering plants. Here, the time during which a stigma is receptive is evaluated and related to the secretion of AGPs in Magnolia virginiana, a protogynous member of an early-divergent angiosperm clade (magnoliids) with a clearly discernible female receptive phase.
  
  
  METHODS
  Magnolia virginiana flower phenology was documented, and histochemical changes in the stigma before and after pollination were examined. Stigmatic receptivity was evaluated in relation to the secretion of AGPs detected in whole mounts and immunolocalized in sectioned stigmas.
  
  
  RESULTS
  Protogynous Magnolia flowers had a precise window of stigmatic receptivity, which is concomitant with the secretion of two AGPs labeled for different epitopes. After pollen germination and tube growth, these two AGPs could no longer be detected in the stigmas, suggesting that these AGPs interact with the growing male gametophytes and could be markers of stigmatic receptivity.
  
  
  CONCLUSIONS
  These results show that the period of stigmatic receptivity is finely coordinated with the secretion of two arabinogalactan proteins on stigmas of flowers of M. virginiana. This first report of AGP presence in stigmatic tissues in a member of the magnoliids, together with recently described similar patterns in eudicots, monocots, and members of early-divergent lineages of flowering plants, suggests an ancient and widespread role for AGPs on stigmatic receptivity in angiosperms.
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, Massachusetts 02138 USA Arnold Arboretum of Harvard University, 1300 Centre Street, Boston, Massachusetts 02131 USA.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Losada
authors.affiliation: Department of Pomology, Aula Dei Experimental Station-CSIC, 1005 Avda. Montañana, Zaragoza, Spain 50059.
authors.forename: Maria
authors.initials: M
authors.lastname: Herrero
authors.affiliation: Department of Subtropical Fruits, Instituto de Hortofruticultura Subtropical y Mediterránea "la Mayora," (IHSM la Mayora-CSIC-UMA), Algarrobo-Costa, Málaga, Spain 29750.
authors.forename: Jose I
authors.initials: JI
authors.lastname: Hormaza
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, Massachusetts 02138 USA Arnold Arboretum of Harvard University, 1300 Centre Street, Boston, Massachusetts 02131 USA.
authors.forename: William E
authors.initials: WE
authors.lastname: Friedman
mesh_terms: D002473:Cell Wall / Q000378:metabolism; D035264:Flowers / Q000033:anatomy & histology / Q000502:physiology; D031566:Magnolia / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology*; D009088:Mucoproteins / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D053205:Pollen Tube / Q000033:anatomy & histology / Q000502:physiology; D054817:Pollination
chemical_list: D009088:Mucoproteins; D010940:Plant Proteins; C006619:arabinogalactan proteins
keywords: AGPs; Magnolia; Magnoliaceae; arabinogalactan proteins; flowering; pollen; protogyny; receptivity; stigma; stigmatic receptivity