title: Arabidopsis class I KNOTTED-like homeobox proteins act downstream in the IDA-HAE/HSL2 floral abscission signaling pathway.
abstract: Floral organ abscission in Arabidopsis thaliana is regulated by the putative ligand-receptor system comprising the signaling peptide INFLORESCENCE DEFICIENT IN ABSCISSION (IDA) and the two receptor-like kinases HAESA and HAESA-LIKE2. The IDA signaling pathway presumably activates a MITOGEN-ACTIVATED PROTEIN KINASE (MAPK) cascade to induce separation between abscission zone (AZ) cells. Misexpression of IDA effectuates precocious floral abscission and ectopic cell separation in latent AZ cell regions, which suggests that negative regulators are in place to prevent unrestricted and untimely AZ cell separation. Through a screen for mutations that restore floral organ abscission in ida mutants, we identified three new mutant alleles of the KNOTTED-LIKE HOMEOBOX gene BREVIPEDICELLUS (BP)/KNOTTED-LIKE FROM ARABIDOPSIS THALIANA1 (KNAT1). Here, we show that bp mutants, in addition to shedding their floral organs prematurely, have phenotypic commonalities with plants misexpressing IDA, such as enlarged AZ cells. We propose that BP/KNAT1 inhibits floral organ cell separation by restricting AZ cell size and number and put forward a model whereby IDA signaling suppresses BP/KNAT1, which in turn allows KNAT2 and KNAT6 to induce floral organ abscission.
authors: Department of Molecular Biosciences, University of Oslo, N-0316 Oslo, Norway.
authors: Chun-Lin
authors: CL
authors: Shi
authors: Grethe-Elisabeth
authors: GE
authors: Stenvik
authors: Ane Kjersti
authors: AK
authors: Vie
authors: Atle M
authors: AM
authors: Bones
authors: Véronique
authors: V
authors: Pautot
authors: Marcel
authors: M
authors: Proveniers
authors: Reidunn B
authors: RB
authors: Aalen
authors: Melinka A
authors: MA
authors: Butenko
mesh_terms: D017360:Arabidopsis / Q000033:anatomy & histology* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D035264:Flowers / Q000502:physiology* / Q000648:ultrastructure; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D009154:Mutation; D010641:Phenotype; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D018398:Homeodomain Proteins; C512213:IDA protein, Arabidopsis; C092212:KNAT1 protein, Arabidopsis; C092213:KNAT2 protein, Arabidopsis; C491111:KNAT6 protein, Arabidopsis; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C089427:RLK5 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases