title: TEMPRANILLO Reveals the Mesophyll as Crucial for Epidermal Trichome Formation.
abstract: Plant trichomes are defensive specialized epidermal cells. In all accepted models, the epidermis is the layer involved in trichome formation, a process controlled by gibberellins (GAs) in Arabidopsis rosette leaves. Indeed, GA activates a genetic cascade in the epidermis for trichome initiation. Here we report that TEMPRANILLO (TEM) genes negatively control trichome initiation not only from the epidermis but also from the leaf layer underneath the epidermis, the mesophyll. Plants over-expressing or reducing TEM specifically in the mesophyll, display lower or higher trichome numbers, respectively. We surprisingly found that fluorescently labeled GA3 accumulates exclusively in the mesophyll of leaves, but not in the epidermis, and that TEM reduces its accumulation and the expression of several newly identified GA transporters. This strongly suggests that TEM plays an essential role, not only in GA biosynthesis, but also in regulating GA distribution in the mesophyll, which in turn directs epidermal trichome formation. Moreover, we show that TEM also acts as a link between GA and cytokinin signaling in the epidermis by negatively regulating downstream genes of both trichome formation pathways. Overall, these results call for a re-evaluation of the present theories of trichome formation as they reveal mesophyll essential during epidermal trichome initiation.
authors.affiliation: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, Campus UAB, Bellaterra (Cerdanyola del Vallès) 08193 Barcelona, Spain (L.M.-H., A.E.A.-J., M.O., P.S.-L., S.P.); ICREA (Institució Catalana de Recerca i Estudis Avançats), Barcelona, Spain (S.P.); and Department of Molecular Biology and Ecology of Plants, Faculty of Life Sciences, Tel Aviv University, 39040, Tel Aviv, Israel (R.W., E.S.).
authors.forename: Luis
authors.identifier: http://orcid.org/0000-0001-5626-9576
authors.initials: L
authors.lastname: Matías-Hernández
authors.affiliation: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, Campus UAB, Bellaterra (Cerdanyola del Vallès) 08193 Barcelona, Spain (L.M.-H., A.E.A.-J., M.O., P.S.-L., S.P.); ICREA (Institució Catalana de Recerca i Estudis Avançats), Barcelona, Spain (S.P.); and Department of Molecular Biology and Ecology of Plants, Faculty of Life Sciences, Tel Aviv University, 39040, Tel Aviv, Israel (R.W., E.S.).
authors.forename: Andrea E
authors.initials: AE
authors.lastname: Aguilar-Jaramillo
authors.affiliation: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, Campus UAB, Bellaterra (Cerdanyola del Vallès) 08193 Barcelona, Spain (L.M.-H., A.E.A.-J., M.O., P.S.-L., S.P.); ICREA (Institució Catalana de Recerca i Estudis Avançats), Barcelona, Spain (S.P.); and Department of Molecular Biology and Ecology of Plants, Faculty of Life Sciences, Tel Aviv University, 39040, Tel Aviv, Israel (R.W., E.S.).
authors.forename: Michela
authors.initials: M
authors.lastname: Osnato
authors.affiliation: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, Campus UAB, Bellaterra (Cerdanyola del Vallès) 08193 Barcelona, Spain (L.M.-H., A.E.A.-J., M.O., P.S.-L., S.P.); ICREA (Institució Catalana de Recerca i Estudis Avançats), Barcelona, Spain (S.P.); and Department of Molecular Biology and Ecology of Plants, Faculty of Life Sciences, Tel Aviv University, 39040, Tel Aviv, Israel (R.W., E.S.).
authors.forename: Roy
authors.identifier: http://orcid.org/0000-0002-1300-6802
authors.initials: R
authors.lastname: Weinstain
authors.affiliation: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, Campus UAB, Bellaterra (Cerdanyola del Vallès) 08193 Barcelona, Spain (L.M.-H., A.E.A.-J., M.O., P.S.-L., S.P.); ICREA (Institució Catalana de Recerca i Estudis Avançats), Barcelona, Spain (S.P.); and Department of Molecular Biology and Ecology of Plants, Faculty of Life Sciences, Tel Aviv University, 39040, Tel Aviv, Israel (R.W., E.S.).
authors.forename: Eilon
authors.initials: E
authors.lastname: Shani
authors.affiliation: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, Campus UAB, Bellaterra (Cerdanyola del Vallès) 08193 Barcelona, Spain (L.M.-H., A.E.A.-J., M.O., P.S.-L., S.P.); ICREA (Institució Catalana de Recerca i Estudis Avançats), Barcelona, Spain (S.P.); and Department of Molecular Biology and Ecology of Plants, Faculty of Life Sciences, Tel Aviv University, 39040, Tel Aviv, Israel (R.W., E.S.).
authors.forename: Paula
authors.identifier: http://orcid.org/0000-0001-5748-9263
authors.initials: P
authors.lastname: Suárez-López
authors.affiliation: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB-UB, Campus UAB, Bellaterra (Cerdanyola del Vallès) 08193 Barcelona, Spain (L.M.-H., A.E.A.-J., M.O., P.S.-L., S.P.); ICREA (Institució Catalana de Recerca i Estudis Avançats), Barcelona, Spain (S.P.); and Department of Molecular Biology and Ecology of Plants, Faculty of Life Sciences, Tel Aviv University, 39040, Tel Aviv, Israel (R.W., E.S.) soraya.pelaz@cragenomica.es.
authors.forename: Soraya
authors.identifier: http://orcid.org/0000-0001-7699-9330
authors.initials: S
authors.lastname: Pelaz
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003583:Cytokinins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005875:Gibberellins / Q000378:metabolism; D056626:Inflorescence / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D009154:Mutation; D019441:Plant Epidermis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D064201:Trichomes / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D029681:Arabidopsis Proteins; D003583:Cytokinins; D005875:Gibberellins; D020033:Protein Isoforms; C533191:TEM1 protein, Arabidopsis; D014157:Transcription Factors