title: MicroRNA miR396 Regulates the Switch between Stem Cells and Transit-Amplifying Cells in Arabidopsis Roots.
abstract: To ensure an adequate organ mass, the daughters of stem cells progress through a transit-amplifying phase displaying rapid cell division cycles before differentiating. Here, we show that Arabidopsis thaliana microRNA miR396 regulates the transition of root stem cells into transit-amplifying cells by interacting with GROWTH-REGULATING FACTORs (GRFs). The GRFs are expressed in transit-amplifying cells but are excluded from the stem cells through inhibition by miR396. Inactivation of the GRFs increases the meristem size and induces periclinal formative divisions in transit-amplifying cells. The GRFs repress PLETHORA (PLT) genes, regulating their spatial expression gradient. Conversely, PLT activates MIR396 in the stem cells to repress the GRFs. We identified a pathway regulated by GRF transcription factors that represses stem cell-promoting genes in actively proliferating cells, which is essential for the progression of the cell cycle and the orientation of the cell division plane. If unchecked, the expression of the GRFs in the stem cell niche suppresses formative cell divisions and distorts the organization of the quiescent center. We propose that the interactions identified here between miR396 and GRF and PLT transcription factors are necessary to establish the boundary between the stem cell niche and the transit-amplifying region.
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario, CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, 2000 Rosario, Argentina rrodriguez@ibr-conicet.gov.ar palatnik@ibr-conicet.gov.ar.
authors.forename: Ramiro E
authors.identifier: http://orcid.org/0000-0002-0867-4099
authors.initials: RE
authors.lastname: Rodriguez
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario, CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, 2000 Rosario, Argentina.
authors.forename: María Florencia
authors.identifier: http://orcid.org/0000-0001-5587-6227
authors.initials: MF
authors.lastname: Ercoli
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario, CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, 2000 Rosario, Argentina.
authors.forename: Juan Manuel
authors.identifier: http://orcid.org/0000-0002-4591-7061
authors.initials: JM
authors.lastname: Debernardi
authors.affiliation: Department of Biology and Howard Hughes Medical Institute, Duke University, Durham, North Carolina 27708.
authors.forename: Natalie W
authors.identifier: http://orcid.org/0000-0001-8517-885X
authors.initials: NW
authors.lastname: Breakfield
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario, CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, 2000 Rosario, Argentina.
authors.forename: Martin A
authors.initials: MA
authors.lastname: Mecchia
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario, CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, 2000 Rosario, Argentina.
authors.forename: Martin
authors.identifier: http://orcid.org/0000-0001-9560-017X
authors.initials: M
authors.lastname: Sabatini
authors.affiliation: Department of Plant Systems Biology, VIB, 9052 Ghent, Belgium Department of Plant Biotechnology and Bioinformatics, Ghent University, B-9052 Ghent, Belgium.
authors.forename: Toon
authors.identifier: http://orcid.org/0000-0002-1258-5531
authors.initials: T
authors.lastname: Cools
authors.affiliation: Department of Plant Systems Biology, VIB, 9052 Ghent, Belgium Department of Plant Biotechnology and Bioinformatics, Ghent University, B-9052 Ghent, Belgium.
authors.forename: Lieven
authors.initials: L
authors.lastname: De Veylder
authors.affiliation: Department of Biology and Howard Hughes Medical Institute, Duke University, Durham, North Carolina 27708.
authors.forename: Philip N
authors.initials: PN
authors.lastname: Benfey
authors.affiliation: Instituto de Biología Molecular y Celular de Rosario, CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, 2000 Rosario, Argentina rrodriguez@ibr-conicet.gov.ar palatnik@ibr-conicet.gov.ar.
authors.forename: Javier F
authors.identifier: http://orcid.org/0000-0001-7996-5224
authors.initials: JF
authors.lastname: Palatnik
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division; D018506:Gene Expression Regulation, Plant; D018519:Meristem / Q000166:cytology / Q000235:genetics / Q000254:growth & development; D035683:MicroRNAs / Q000235:genetics*; D018517:Plant Roots / Q000166:cytology / Q000235:genetics / Q000254:growth & development; D030821:Plants, Genetically Modified; D055153:Stem Cell Niche / Q000235:genetics; D013234:Stem Cells; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C572930:MIRN396 microRNA, Arabidopsis; D035683:MicroRNAs; D014157:Transcription Factors