title: Cytokinins determine Arabidopsis root-meristem size by controlling cell differentiation.
abstract: Plant postembryonic development takes place in the meristems, where stem cells self-renew and produce daughter cells that differentiate and give rise to different organ structures. For the maintenance of meristems, the rate of differentiation of daughter cells must equal the generation of new cells: How this is achieved is a central question in plant development. In the Arabidopsis root meristem, stem cells surround a small group of organizing cells, the quiescent center. Together they form a stem cell niche [1, 2], whose position and activity depends on the combinatorial action of two sets of genes - PLETHORA1 (PLT1) and PLETHORA2 (PLT2)[3, 4] and SCARECROW (SCR) and SHORTROOT (SHR)[2] - as well as on polar auxin transport. In contrast, the mechanisms controlling meristematic cell differentiation remain unclear. Here, we report that cytokinins control the rate of meristematic cell differentiation and thus determine root-meristem size via a two-component receptor histidine kinase-transcription factor signaling pathway. Analysis of the root meristems of cytokinin mutants, spatial cytokinin depletion, and exogenous cytokinin application indicates that cytokinins act in a restricted region of the root meristem, where they antagonize a non-cell-autonomous cell-division signal, and we provide evidence that this signal is auxin.
authors.affiliation: Dipartimento di Genetica e Biologia Molecolare, Laboratory of Functional Genomics and Proteomics of Model Systems, Università La Sapienza, Rome, Italy.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Dello Ioio
authors.forename: Francisco Scaglia
authors.initials: FS
authors.lastname: Linhares
authors.forename: Emanuele
authors.initials: E
authors.lastname: Scacchi
authors.forename: Eva
authors.initials: E
authors.lastname: Casamitjana-Martinez
authors.forename: Renze
authors.initials: R
authors.lastname: Heidstra
authors.forename: Paolo
authors.initials: P
authors.lastname: Costantino
authors.forename: Sabrina
authors.initials: S
authors.lastname: Sabatini
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000378:metabolism; D002454:Cell Differentiation; D003583:Cytokinins / Q000378:metabolism*; D018519:Meristem / Q000166:cytology*; D018517:Plant Roots / Q000166:cytology* / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D003583:Cytokinins