title: Arabidopsis DELLA and two HD-ZIP transcription factors regulate GA signaling in the epidermis through the L1 box cis-element.
abstract: Gibberellins (GAs) are plant hormones that affect plant growth and regulate gene expression differentially across tissues. To study the molecular mechanisms underlying GA signaling in Arabidopsis thaliana, we focused on a GDSL lipase gene (LIP1) induced by GA and repressed by DELLA proteins. LIP1 contains an L1 box promoter sequence, conserved in the promoters of epidermis-specific genes, that is bound by ATML1, an HD-ZIP transcription factor required for epidermis specification. In this study, we demonstrate that LIP1 is specifically expressed in the epidermis and that its L1 box sequence mediates GA-induced transcription. We show that this sequence is overrepresented in the upstream regulatory regions of GA-induced and DELLA-repressed transcriptomes and that blocking GA signaling in the epidermis represses the expression of L1 box-containing genes and negatively affects seed germination. We show that DELLA proteins interact directly with ATML1 and its paralogue PDF2 and that silencing of both HD-ZIP transcription factors inhibits epidermal gene expression and delays germination. Our results indicate that, upon seed imbibition, increased GA levels reduce DELLA protein abundance and release ATML1/PDF2 to activate L1 box gene expression, thus enhancing germination potential.
authors.affiliation: Centro de Biotecnología y Genómica de Plantas, UPM-INIA, and E.T.S.I. Agrónomos, Universidad Politécnica de Madrid, Campus de Montegancedo, Pozuelo de Alarcón, 28223 Madrid, Spain.
authors.forename: Belén
authors.initials: B
authors.lastname: Rombolá-Caldentey
authors.affiliation: Centro de Biotecnología y Genómica de Plantas, UPM-INIA, and E.T.S.I. Agrónomos, Universidad Politécnica de Madrid, Campus de Montegancedo, Pozuelo de Alarcón, 28223 Madrid, Spain.
authors.forename: Paloma
authors.initials: P
authors.lastname: Rueda-Romero
authors.affiliation: Centro de Biotecnología y Genómica de Plantas, UPM-INIA, and E.T.S.I. Agrónomos, Universidad Politécnica de Madrid, Campus de Montegancedo, Pozuelo de Alarcón, 28223 Madrid, Spain.
authors.forename: Raquel
authors.initials: R
authors.lastname: Iglesias-Fernández
authors.affiliation: Centro de Biotecnología y Genómica de Plantas, UPM-INIA, and E.T.S.I. Agrónomos, Universidad Politécnica de Madrid, Campus de Montegancedo, Pozuelo de Alarcón, 28223 Madrid, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: Carbonero
authors.affiliation: Centro de Biotecnología y Genómica de Plantas, UPM-INIA, and E.T.S.I. Agrónomos, Universidad Politécnica de Madrid, Campus de Montegancedo, Pozuelo de Alarcón, 28223 Madrid, Spain luis.onate@upm.es.
authors.forename: Luis
authors.initials: L
authors.lastname: Oñate-Sánchez
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D018525:Germination; D005875:Gibberellins / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D008957:Models, Genetic; D019441:Plant Epidermis / Q000166:cytology / Q000235:genetics / Q000502:physiology; D010937:Plant Growth Regulators / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins; D012639:Seeds / Q000166:cytology / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction; D014026:Nicotiana / Q000166:cytology / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: C103790:ATML1 protein, Arabidopsis; D029681:Arabidopsis Proteins; C109555:GAI protein, Arabidopsis; D005875:Gibberellins; D018398:Homeodomain Proteins; C472305:PDF2 protein, Arabidopsis; D010937:Plant Growth Regulators; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors