title: Arabidopsis VASCULAR-RELATED UNKNOWN PROTEIN1 regulates xylem development and growth by a conserved mechanism that modulates hormone signaling.
abstract: Despite a strict conservation of the vascular tissues in vascular plants (tracheophytes), our understanding of the genetic basis underlying the differentiation of secondary cell wall-containing cells in the xylem of tracheophytes is still far from complete. Using coexpression analysis and phylogenetic conservation across sequenced tracheophyte genomes, we identified a number of Arabidopsis (Arabidopsis thaliana) genes of unknown function whose expression is correlated with secondary cell wall deposition. Among these, the Arabidopsis VASCULAR-RELATED UNKNOWN PROTEIN1 (VUP1) gene encodes a predicted protein of 24 kD with no annotated functional domains but containing domains that are highly conserved in tracheophytes. Here, we show that the VUP1 expression pattern, determined by promoter-β-glucuronidase reporter gene expression, is associated with vascular tissues, while vup1 loss-of-function mutants exhibit collapsed morphology of xylem vessel cells. Constitutive overexpression of VUP1 caused dramatic and pleiotropic developmental defects, including severe dwarfism, dark green leaves, reduced apical dominance, and altered photomorphogenesis, resembling brassinosteroid-deficient mutants. Constitutive overexpression of VUP homologs from multiple tracheophyte species induced similar defects. Whole-genome transcriptome analysis revealed that overexpression of VUP1 represses the expression of many brassinosteroid- and auxin-responsive genes. Additionally, deletion constructs and site-directed mutagenesis were used to identify critical domains and amino acids required for VUP1 function. Altogether, our data suggest a conserved role for VUP1 in regulating secondary wall formation during vascular development by tissue- or cell-specific modulation of hormone signaling pathways.
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: Etienne
authors.initials: E
authors.lastname: Grienenberger
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Douglas
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D060406:Brassinosteroids / Q000378:metabolism; D000460:Chlorophyta / Q000378:metabolism; D019295:Computational Biology; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D017343:Genes, Plant; D056626:Inflorescence / Q000033:anatomy & histology / Q000378:metabolism; D008027:Light; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010641:Phenotype; D010766:Phosphorylation / Q000528:radiation effects; D010937:Plant Growth Regulators / Q000378:metabolism*; D058526:Plant Vascular Bundle / Q000235:genetics / Q000528:radiation effects; D011401:Promoter Regions, Genetic / Q000235:genetics; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000528:radiation effects; D012326:RNA Splicing / Q000235:genetics / Q000528:radiation effects; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D036226:Seedlings / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics / Q000528:radiation effects; D013347:Subcellular Fractions / Q000378:metabolism; D052584:Xylem / Q000254:growth & development* / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; D060406:Brassinosteroids; D010937:Plant Growth Regulators; D011993:Recombinant Fusion Proteins; C000593210:VASCULAR-RELATED UNKNOWN PROTEIN1, Arabidopsis