title: microRNA-directed cleavage of ATHB15 mRNA regulates vascular development in Arabidopsis inflorescence stems.
abstract: Class III homeodomain-leucine zipper proteins regulate critical aspects of plant development, including lateral organ polarity, apical and lateral meristem formation, and vascular development. ATHB15, a member of this transcription factor family, is exclusively expressed in vascular tissues. Recently, a microRNA (miRNA) binding sequence has been identified in ATHB15 mRNA, suggesting that a molecular mechanism governed by miRNA binding may direct vascular development through ATHB15. Here, we show that miR166-mediated ATHB15 mRNA cleavage is a principal mechanism for the regulation of vascular development. In a gain-of-function MIR166a mutant, the decreased transcript level of ATHB15 was accompanied by an altered vascular system with expanded xylem tissue and interfascicular region, indicative of accelerated vascular cell differentiation from cambial/procambial cells. A similar phenotype was observed in Arabidopsis plants with reduced ATHB15 expression but reversed in transgenic plants overexpressing an miR166-resistant ATHB15. ATHB15 mRNA cleavage occurred in standard wheat germ extracts and in Arabidopsis and was mediated by miR166 in Nicotiana benthamiana cells. miR166-assisted ATHB15 repression is likely to be a conserved mechanism that regulates vascular development in all vascular plants.
authors.affiliation: Graduate School of Chemistry and Molecular Engineering, Seoul National University, Seoul 151-742, South Korea.
authors.forename: Joonki
authors.initials: J
authors.lastname: Kim
authors.forename: Jae-Hoon
authors.initials: JH
authors.lastname: Jung
authors.forename: Jose L
authors.initials: JL
authors.lastname: Reyes
authors.forename: Youn-Sung
authors.initials: YS
authors.lastname: Kim
authors.forename: Sun-Young
authors.initials: SY
authors.lastname: Kim
authors.forename: Kyung-Sook
authors.initials: KS
authors.lastname: Chung
authors.forename: Jin A
authors.initials: JA
authors.lastname: Kim
authors.forename: Minsun
authors.initials: M
authors.lastname: Lee
authors.forename: Yoontae
authors.initials: Y
authors.lastname: Lee
authors.forename: V
authors.initials: V
authors.lastname: Narry Kim
authors.forename: Nam-Hai
authors.initials: NH
authors.lastname: Chua
authors.forename: Chung-Mo
authors.initials: CM
authors.lastname: Park
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000502:physiology*; D001483:Base Sequence; D015536:Down-Regulation; D035264:Flowers / Q000254:growth & development; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D018398:Homeodomain Proteins / Q000502:physiology*; D035683:MicroRNAs / Q000502:physiology*; D009154:Mutation; D010641:Phenotype; D018547:Plant Stems / Q000254:growth & development; D012333:RNA, Messenger / Q000502:physiology; D018749:RNA, Plant / Q000502:physiology*; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; C482920:HB-15 protein, Arabidopsis; D018398:Homeodomain Proteins; C580969:MIRN166 microRNA, Arabidopsis; D035683:MicroRNAs; D012333:RNA, Messenger; D018749:RNA, Plant; D014157:Transcription Factors