title: Novel markers of xylogenesis in zinnia are differentially regulated by auxin and cytokinin.
abstract: The characterization of in vitro xylogenic cultures of zinnia (Zinnia elegans) has led to major discoveries in the understanding of xylem formation in plants. We have constructed and characterized a subtractive library from zinnia cultures enriched in genes that are specifically expressed at the onset of secondary wall deposition and tracheary element (TE) programmed cell death. This Late Xylogenesis Library (LXL) consisted of 236 nonredundant cDNAs, 77% of which encoded novel sequences in comparison with the 17,622 expressed sequence tag sequences publicly available. cDNA arrays were constructed to examine dynamic global gene expression during the course of TE formation. As a first step in dissecting auxin and cytokinin signaling during TE differentiation, macroarrays were probed with cDNAs from cells cultured in different hormonal conditions. Fifty-one percent of the LXL genes were induced by either auxin or cytokinin individually, the large majority by auxin. To determine the potential involvement of these categories of genes in TE differentiation, multiplex in situ-reverse transcription-PCR was performed on cells for two genes encoding putative cell wall proteins: Gibberellin stimulated transcript-1, induced by auxin alone, and expansin 5, induced by cytokinin alone. All transcriptionally active TEs expressed both genes, indicating that, although these genes may not be considered as specific markers for TE differentiation per se, they are nevertheless an integral part of TE differentiation program. Among the non-TE population, four different gene expression-based cell types could be distinguished. Together, these results demonstrate the underlying complexity of hormonal perception and the existence of several different cell types in in vitro TE cell cultures.
authors.affiliation: Unité Mixte de Recherche, Centre National de la Recherche Scientifique/Université Paul Sabatier 5546, Surfaces Cellulaires et Signalisation chez les Végétaux, Pôle de Biotechnologie Végétale, 31326 Castanet, Tolosan, France.
authors.forename: Edouard
authors.initials: E
authors.lastname: Pesquet
authors.forename: Philippe
authors.initials: P
authors.lastname: Ranocha
authors.forename: Sylvain
authors.initials: S
authors.lastname: Legay
authors.forename: Catherine
authors.initials: C
authors.lastname: Digonnet
authors.forename: Odile
authors.initials: O
authors.lastname: Barbier
authors.forename: Magalie
authors.initials: M
authors.lastname: Pichon
authors.forename: Deborah
authors.initials: D
authors.lastname: Goffner
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D017360:Arabidopsis; D019659:Asteraceae / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development*; D001483:Base Sequence; D002473:Cell Wall / Q000235:genetics; D019295:Computational Biology; D003583:Cytokinins / Q000494:pharmacology*; D018744:DNA, Plant / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D015723:Gene Library; D017343:Genes, Plant / Q000187:drug effects; D023281:Genomics; D007210:Indoleacetic Acids / Q000494:pharmacology*; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D010937:Plant Growth Regulators / Q000494:pharmacology*; D013045:Species Specificity
chemical_list: D003583:Cytokinins; D018744:DNA, Plant; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators