title: Asymmetric leaves2 and Elongator, a histone acetyltransferase complex, mediate the establishment of polarity in leaves of Arabidopsis thaliana.
abstract: Leaf primordia are generated around the shoot apical meristem. Mutation of the ASYMMETRIC LEAVES2 (AS2) gene of Arabidopsis thaliana results in defects in repression of the meristematic and indeterminate state, establishment of adaxial-abaxial polarity and left-right symmetry in leaves. AS2 represses transcription of meristem-specific class 1 KNOX homeobox genes and of the abaxial-determinant genes ETTIN/ARF3, KANADI2 and YABBY5. To clarify the role of AS2 in the establishment of leaf polarity, we isolated mutations that enhanced the polarity defects associated with as2. We describe here the enhancer-of-asymmetric-leaves-two1 (east1) mutation, which caused the formation of filamentous leaves with abaxialized epidermis on the as2-1 background. Levels of transcripts of class 1 KNOX and abaxial-determinant genes were markedly higher in as2-1 east1-1 mutant plants than in the wild-type and corresponding single-mutant plants. EAST1 encodes the histone acetyltransferase ELONGATA3 (ELO3), a component of the Elongator complex. Genetic analysis, using mutations in genes involved in the biogenesis of a trans-acting small interfering RNA (ta-siRNA), revealed that ELO3 mediated establishment of leaf polarity independently of AS2 and the ta-siRNA-related pathway. Treatment with an inhibitor of histone deacetylases (HDACs) caused additive polarity defects in as2-1 east1-1 mutant plants, suggesting the operation of an ELO3 pathway, independent of the HDAC pathway, in the determination of polarity. We propose that multiple pathways play important roles in repression of the expression of class 1 KNOX and abaxial-determinant genes in the development of the adaxial domain of leaves and, thus, in the establishment of leaf polarity.
authors.affiliation: Graduate School of Bioscience and Biotechnology, Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi, 487-8501 Japan.
authors.forename: Shoko
authors.initials: S
authors.lastname: Kojima
authors.forename: Mayumi
authors.initials: M
authors.lastname: Iwasaki
authors.forename: Hiro
authors.initials: H
authors.lastname: Takahashi
authors.forename: Tomoya
authors.initials: T
authors.lastname: Imai
authors.forename: Yoko
authors.initials: Y
authors.lastname: Matsumura
authors.forename: Delphine
authors.initials: D
authors.lastname: Fleury
authors.forename: Mieke
authors.initials: M
authors.lastname: Van Lijsebettens
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Machida
authors.forename: Chiyoko
authors.initials: C
authors.lastname: Machida
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D019070:Cell Lineage / Q000187:drug effects; D016764:Cell Polarity; D002874:Chromosome Mapping; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D051548:Histone Acetyltransferases / Q000235:genetics / Q000378:metabolism*; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006877:Hydroxamic Acids / Q000494:pharmacology; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D018515:Plant Leaves / Q000166:cytology* / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C463739:AS2 protein, Arabidopsis; C456239:ASYMMETRIC LEAVES1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D014157:Transcription Factors; C486145:ZIPPY protein, Arabidopsis; C012589:trichostatin A; C502551:ELO3 protein, Arabidopsis; D051548:Histone Acetyltransferases; C514575:RDR6 protein, Arabidopsis; D012324:RNA-Dependent RNA Polymerase