title: Coordination of auxin-triggered leaf initiation by tomatoLEAFLESS.
abstract: Lateral plant organs, particularly leaves, initiate at the flanks of the shoot apical meristem (SAM) following auxin maxima signals; however, little is known about the underlying mechanisms. Here, we show that tomatoleafless(lfs) mutants fail to produce cotyledons and leaves and grow a naked pin while maintaining an active SAM. A similar phenotype was observed among pin-like shoots induced by polar auxin transport inhibitors such as 2,3,5-triiodobenzoic acid (TIBA). Both types of pin-like shoots showed reduced expression of primordia markers as well as abnormal auxin distribution, as evidenced by expression of the auxin reporterspPIN1:PIN1:GFPandDR5:YFPUpon auxin microapplication, bothlfsmeristems and TIBA-pin apices activatedDR5:YFPexpression with similar kinetics; however, onlylfsplants failed to concurrently initiate leaf primordia. We found thatLFSencodes the single tomato ortholog ofArabidopsis DORNRONSCHEN(DRN) andDRN-like(DRNL) genes and is transiently expressed at incipient and young primordia, overlapping with auxin response maxima.LFSis rapidly induced by auxin application, implying feed-forward activity betweenLFSand auxin signals. However, drivingLFSat auxin response maxima sites using theDR5promoter fails to fully rescuelfsplants, suggesting that additional, auxin-independent regulation is needed. Indeed, extended GCC-box elements upstream ofLFSdrove primordia-specific expression in a LFS-dependent but auxin-independent manner. We thus suggest thatLFStransiently acts at the site of primordia initiation, where it provides a specific context to auxin response maxima culminating in leaf primordia initiation.
authors.affiliation: Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel 7610001.|Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel 76100.
authors.forename: Yossi
authors.initials: Y
authors.lastname: Capua
authors.affiliation: Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel 7610001; yuval.eshed@weizmann.ac.il.
authors.forename: Yuval
authors.initials: Y
authors.lastname: Eshed
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D056726:Genetic Association Studies; D007210:Indoleacetic Acids / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D009154:Mutation; D010641:Phenotype; D010802:Phylogeny; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D020218:Response Elements; D015398:Signal Transduction
chemical_list: D007210:Indoleacetic Acids
keywords: DRN/DRNL; SAM; TIBA pins; extended GCC-box; lateral organ formation