title: The RADICLELESS1 gene is required for vascular pattern formation in rice.
abstract: The molecular mechanisms through which the complex patterns of plant vascular tissues are established are largely unknown. The highly ordered, yet simple, striate array of veins of rice leaves represents an attractive system to study the dynamics underlying pattern formation. Here we show that mutation in the RADICLELESS1 (RAL1) gene results in distinctive vascular pattern defects. In ral1 embryonic scutella, secondary veins are absent and in the prematurely aborted and discontinuous primary veins, cells are misaligned to each other. In ral1 leaves, longitudinal and commissural (transverse) veins display altered spacing and the commissural veins additionally show atypical branching and interruptions in their continuity. The vascular pattern alterations of ral1 occur in the context of normally shaped leaf primordia. Anatomical inspection and analysis of the expression of the procambium specification marker Oshox1-GUS and of the auxin-inducible reporter DR5-GUS demonstrates that all the vascular patterning aberrations of ral1 originate from defects in the procambium, which represents the earliest identifiable stage of vascular development. Furthermore, the ral1 mutant is unique in that procambium formation in leaf primordium development is delayed. Finally, the ral1 vascular patterning distortions are associated with a defective response to auxin and with an enhanced sensitivity to cytokinin. ral1 is the first mutant impaired in both procambium development and vascular patterning to be isolated in a monocot species.
authors.affiliation: Institute of Molecular Plant Sciences, Leiden University, Clusius Laboratory, PO Box 9505, 2300 RA Leiden, The Netherlands.
authors.forename: Enrico
authors.initials: E
authors.lastname: Scarpella
authors.forename: Saskia
authors.initials: S
authors.lastname: Rueb
authors.forename: Annemarie H
authors.initials: AH
authors.lastname: Meijer
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001593:Benzyl Compounds; D015415:Biomarkers; D003583:Cytokinins / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D007210:Indoleacetic Acids / Q000494:pharmacology; D007701:Kinetin; D009154:Mutation; D012275:Oryza / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*; D018515:Plant Leaves / Q000033:anatomy & histology / Q000235:genetics / Q000254:growth & development; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development; D011687:Purines; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000187:drug effects / Q000235:genetics; D012098:Reproduction / Q000235:genetics; D012639:Seeds / Q000033:anatomy & histology / Q000187:drug effects; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001593:Benzyl Compounds; D015415:Biomarkers; D003583:Cytokinins; D018398:Homeodomain Proteins; D007210:Indoleacetic Acids; C106325:Oshox1 protein, Oryza sativa; D010940:Plant Proteins; D011687:Purines; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D014157:Transcription Factors; D000225:Adenine; C480551:benzylaminopurine; D007701:Kinetin