title: Galactoglucomannans increase cell population density and alter the protoxylem/metaxylem tracheary element ratio in xylogenic cultures of Zinnia.
abstract: Xylogenic cultures of zinnia (Zinnia elegans) provide a unique opportunity to study signaling pathways of tracheary element (TE) differentiation. In vitro TEs differentiate into either protoxylem (PX)-like TEs characterized by annular/helical secondary wall thickening or metaxylem (MX)-like TEs with reticulate/scalariform/pitted thickening. The factors that determine these different cell fates are largely unknown. We show here that supplementing zinnia cultures with exogenous galactoglucomannan oligosaccharides (GGMOs) derived from spruce (Picea abies) xylem had two major effects: an increase in cell population density and a decrease in the ratio of PX to MX TEs. In an attempt to link these two effects, the consequence of the plane of cell division on PX-MX differentiation was assessed. Although GGMOs did not affect the plane of cell division per se, they significantly increased the proportion of longitudinally divided cells differentiating into MX. To test the biological significance of these findings, we have determined the presence of mannan-containing oligosaccharides in zinnia cultures in vitro. Immunoblot assays indicated that beta-1,4-mannosyl epitopes accumulate specifically in TE-inductive media. These epitopes were homogeneously distributed within the thickened secondary walls of TEs when the primary cell wall was weakly labeled. Using polysaccharide analysis carbohydrate gel electrophoresis, glucomannans were specifically detected in cell walls of differentiating zinnia cultures. Finally, zinnia macroarrays probed with cDNAs from cells cultured in the presence or absence of GGMOs indicated that significantly more genes were down-regulated rather than up-regulated by GGMOs. This study constitutes a major step in the elucidation of signaling mechanisms of PX- and MX-specific genetic programs in zinnia.
authors.affiliation: Unité Mixte de Recherche, Centre National de la Recherche Scientifique, Université Paul Sabatier 5546, Pôle de Biotechnologie Végétale, 31326 Castanet-Tolosan, France.
authors.forename: Anna
authors.initials: A
authors.lastname: Benová-Kákosová
authors.forename: Catherine
authors.initials: C
authors.lastname: Digonnet
authors.forename: Florence
authors.initials: F
authors.lastname: Goubet
authors.forename: Philippe
authors.initials: P
authors.lastname: Ranocha
authors.forename: Alain
authors.initials: A
authors.lastname: Jauneau
authors.forename: Edouard
authors.initials: E
authors.lastname: Pesquet
authors.forename: Odile
authors.initials: O
authors.lastname: Barbier
authors.forename: Zhinong
authors.initials: Z
authors.lastname: Zhang
authors.forename: Peter
authors.initials: P
authors.lastname: Capek
authors.forename: Paul
authors.initials: P
authors.lastname: Dupree
authors.forename: Desana
authors.initials: D
authors.lastname: Lisková
authors.forename: Deborah
authors.initials: D
authors.lastname: Goffner
mesh_terms: D019659:Asteraceae / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division; D003470:Culture Media / Q000737:chemistry; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D008351:Mannans / Q000494:pharmacology*; D008969:Molecular Sequence Data; D046509:Tissue Culture Techniques; D052584:Xylem / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism
chemical_list: D003470:Culture Media; D008351:Mannans