title: Root border-like cells of Arabidopsis. Microscopical characterization and role in the interaction with rhizobacteria.
abstract: Plant roots of many species produce thousands of cells that are released daily into the rhizosphere. These cells are commonly termed border cells because of their major role in constituting a biotic boundary layer between the root surface and the soil. In this study, we investigated the occurrence and ultrastructure of such cells in Arabidopsis (Arabidopsis thaliana) using light and electron microscopy coupled to high-pressure freezing. The secretion of cell wall molecules including pectic polysaccharides and arabinogalactan-proteins (AGPs) was examined also using immunofluorescence microscopy and a set of anticarbohydrate antibodies. We show that root tips of Arabidopsis seedlings released cell layers in an organized pattern that differs from the rather randomly dispersed release observed in other plant species studied to date. Therefore, we termed such cells border-like cells (BLC). Electron microscopical results revealed that BLC are rich in mitochondria, Golgi stacks, and Golgi-derived vesicles, suggesting that these cells are actively engaged in secretion of materials to their cell walls. Immunocytochemical data demonstrated that pectins as well as AGPs are among secreted material as revealed by the high level of expression of AGP-epitopes. In particular, the JIM13-AGP epitope was found exclusively associated with BLC and peripheral cells in the root cap region. In addition, we investigated the function of BLC and root cap cell AGPs in the interaction with rhizobacteria using AGP-disrupting agents and a strain of Rhizobium sp. expressing a green fluorescent protein. Our findings demonstrate that alteration of AGPs significantly inhibits the attachment of the bacteria to the surface of BLC and root tip.
authors.affiliation: Unité Mixte de Recherche Centre National de la Recherche Scientifique 6037, Institut Fédératif de Recherches Multidisciplinaires sur les Peptides 23, Centre Commun de Microscopie Electronique, Université de Rouen, 76821 Mont Saint Aignan, France.
authors.forename: Maïté
authors.initials: M
authors.lastname: Vicré
authors.forename: Catherine
authors.initials: C
authors.lastname: Santaella
authors.forename: Sandrine
authors.initials: S
authors.lastname: Blanchet
authors.forename: Aurélien
authors.initials: A
authors.lastname: Gateau
authors.forename: Azeddine
authors.initials: A
authors.lastname: Driouich
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000378:metabolism / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001422:Bacterial Adhesion / Q000502:physiology; D002473:Cell Wall; D005960:Glucosides; D009088:Mucoproteins / Q000378:metabolism*; D010696:Phloroglucinol / Q000031:analogs & derivatives; D010940:Plant Proteins; D018517:Plant Roots / Q000166:cytology* / Q000378:metabolism / Q000382:microbiology* / Q000648:ultrastructure; D011392:Proline / Q000031:analogs & derivatives; D012231:Rhizobium / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D005960:Glucosides; D009088:Mucoproteins; D010940:Plant Proteins; C104977:Yariv reagent; C006619:arabinogalactan proteins; C002195:3,4-dehydroproline; D011392:Proline; D010696:Phloroglucinol