title: The AtCathB3 gene, encoding a cathepsin B-like protease, is expressed during germination of Arabidopsis thaliana and transcriptionally repressed by the basic leucine zipper protein GBF1.
abstract: Protein hydrolysis plays an important role during seed germination and post-germination seedling establishment. In Arabidopsis thaliana, cathepsin B-like proteases are encoded by a gene family of three members, but only the AtCathB3 gene is highly induced upon seed germination and at the early post-germination stage. Seeds of a homozygous T-DNA insertion mutant in the AtCathB3 gene have, besides a reduced cathepsin B activity, a slower germination than the wild type. To explore the transcriptional regulation of this gene, we used a combined phylogenetic shadowing approach together with a yeast one-hybrid screening of an arrayed library of approximately 1200 transcription factor open reading frames from Arabidopsis thaliana. We identified a conserved CathB3-element in the promoters of orthologous CathB3 genes within the Brassicaceae species analysed, and, as its DNA-interacting protein, the G-Box Binding Factor1 (GBF1). Transient overexpression of GBF1 together with a PAtCathB3::uidA (β-glucuronidase) construct in tobacco plants revealed a negative effect of GBF1 on expression driven by the AtCathB3 promoter. In stable P35S::GBF1 lines, not only was the expression of the AtCathB3 gene drastically reduced, but a significant slower germination was also observed. In the homozygous knockout mutant for the GBF1 gene, the opposite effect was found. These data indicate that GBF1 is a transcriptional repressor of the AtCathB3 gene and affects the germination kinetics of Arabidopsis thaliana seeds. As AtCathB3 is also expressed during post-germination in the cotyledons, a role for the AtCathB3-like protease in reserve mobilization is also inferred.
authors.affiliation: Centro de Biotecnología y Genómica de Plantas (UPM-INIA), and E.T.S.I. Agrónomos, Campus de Montegancedo, Universidad Politécnica de Madrid, Pozuelo de Alarcón, 28223-Madrid, Spain.
authors.forename: Raquel
authors.initials: R
authors.lastname: Iglesias-Fernández
authors.forename: Dorothee
authors.initials: D
authors.lastname: Wozny
authors.forename: Maite
authors.initials: M
authors.lastname: Iriondo-de Hond
authors.forename: Luis
authors.initials: L
authors.lastname: Oñate-Sánchez
authors.forename: Pilar
authors.initials: P
authors.lastname: Carbonero
authors.forename: Cristina
authors.initials: C
authors.lastname: Barrero-Sicilia
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002401:Cathepsin B / Q000235:genetics / Q000378:metabolism; D018548:Cotyledon / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018525:Germination; D005966:Glucuronidase / Q000378:metabolism; D017404:In Situ Hybridization, Fluorescence; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D060888:Real-Time Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C552546:GBF1 protein, Arabidopsis; D010940:Plant Proteins; D014157:Transcription Factors; D005966:Glucuronidase; D002401:Cathepsin B
keywords: Arabidopsis thaliana; AtCathB3; GBF1; bZIP; cathepsin B-like enzymes; phylogenetic shadowing; reserve mobilization; seed germination; transcriptional regulation.