title: The NAC-domain transcription factor GOBLET specifies leaflet boundaries in compound tomato leaves.
abstract: Leaves are formed at the flanks of the shoot apical meristem (SAM) and develop into a variety of forms. In tomato, prolonged leaf patterning enables the elaboration of compound leaves by reiterative initiation of leaflets with lobed margins. In goblet (gob) loss-of-function mutants, primary leaflets are often fused, secondary leaflets and marginal serrations are absent, and SAMs often terminate precociously. We show that GOB encodes a NAC-domain transcription factor expressed in narrow stripes at the leaf margins, flanking the distal side of future leaflet primordia, and at the boundaries between the SAM and leaf primordia. Leaf-specific overexpression of the microRNA miR164, a negative regulator of GOB-like genes, also leads to loss of secondary-leaflet initiation and to smooth leaflet margins. Plants carrying a dominant gob allele with an intact ORF but disrupted miR164 binding site produce more cotyledons and floral organs, have split SAMs and, surprisingly, simpler leaves. Overexpression of a form of GOB with an altered miR164 binding site in leaf primordia leads to delayed leaflet maturation, frequent, improperly timed and spaced initiation events, and a simple mature leaflet form owing to secondary-leaflet fusion. miR164 also affects leaflet separation in Cardamine hirsuta, a Brassicaceae species with complex leaves. Genetic and molecular analyses suggest that GOB expression is intact in the simplified leaves of entire tomato mutants, which have a defect in a putative repressor of auxin responses. Our results show that GOB marks leaflet boundaries and that its accurate spatial, temporal and quantitative activity affects leaf elaboration in a context-dependent manner.
authors.affiliation: The Robert H Smith Institute of Plant Sciences and Genetics in Agriculture and The Otto Warburg Minerva Center for Agricultural Biotechnology, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot, Israel.
authors.forename: Yael
authors.initials: Y
authors.lastname: Berger
authors.forename: Smadar
authors.initials: S
authors.lastname: Harpaz-Saad
authors.forename: Arnon
authors.initials: A
authors.lastname: Brand
authors.forename: Hadas
authors.initials: H
authors.lastname: Melnik
authors.forename: Neti
authors.initials: N
authors.lastname: Sirding
authors.forename: John Paul
authors.initials: JP
authors.lastname: Alvarez
authors.forename: Michael
authors.initials: M
authors.lastname: Zinder
authors.forename: Alon
authors.initials: A
authors.lastname: Samach
authors.forename: Yuval
authors.initials: Y
authors.lastname: Eshed
authors.forename: Naomi
authors.initials: N
authors.lastname: Ori
mesh_terms: D001483:Base Sequence; D019521:Body Patterning / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018551:Solanum lycopersicum / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D018519:Meristem / Q000254:growth & development / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics; D008954:Models, Biological; D009154:Mutation; D010641:Phenotype; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D018749:RNA, Plant / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D035683:MicroRNAs; D010940:Plant Proteins; D018749:RNA, Plant; D014157:Transcription Factors