title: Integration of hormonal signaling networks and mobile microRNAs is required for vascular patterning in Arabidopsis roots.
abstract: As multicellular organisms grow, positional information is continually needed to regulate the pattern in which cells are arranged. In the Arabidopsis root, most cell types are organized in a radially symmetric pattern; however, a symmetry-breaking event generates bisymmetric auxin and cytokinin signaling domains in the stele. Bidirectional cross-talk between the stele and the surrounding tissues involving a mobile transcription factor, SHORT ROOT (SHR), and mobile microRNA species also determines vascular pattern, but it is currently unclear how these signals integrate. We use a multicellular model to determine a minimal set of components necessary for maintaining a stable vascular pattern. Simulations perturbing the signaling network show that, in addition to the mutually inhibitory interaction between auxin and cytokinin, signaling through SHR, microRNA165/6, and PHABULOSA is required to maintain a stable bisymmetric pattern. We have verified this prediction by observing loss of bisymmetry in shr mutants. The model reveals the importance of several features of the network, namely the mutual degradation of microRNA165/6 and PHABULOSA and the existence of an additional negative regulator of cytokinin signaling. These components form a plausible mechanism capable of patterning vascular tissues in the absence of positional inputs provided by the transport of hormones from the shoot.
authors.affiliation: Centre for Plant Integrative Biology, School of Biosciences, University of Nottingham, Loughborough LE12 5RD, United Kingdom.
authors.forename: Daniele
authors.initials: D
authors.lastname: Muraro
authors.forename: Nathan
authors.initials: N
authors.lastname: Mellor
authors.forename: Michael P
authors.initials: MP
authors.lastname: Pound
authors.forename: Hanna
authors.initials: H
authors.lastname: Help
authors.forename: Mikaël
authors.initials: M
authors.lastname: Lucas
authors.forename: Jérôme
authors.initials: J
authors.lastname: Chopard
authors.forename: Helen M
authors.initials: HM
authors.lastname: Byrne
authors.forename: Christophe
authors.initials: C
authors.lastname: Godin
authors.forename: T Charlie
authors.initials: TC
authors.lastname: Hodgman
authors.forename: John R
authors.initials: JR
authors.lastname: King
authors.forename: Tony P
authors.initials: TP
authors.lastname: Pridmore
authors.forename: Ykä
authors.initials: Y
authors.lastname: Helariutta
authors.forename: Malcolm J
authors.initials: MJ
authors.lastname: Bennett
authors.forename: Anthony
authors.initials: A
authors.lastname: Bishopp
mesh_terms: D017360:Arabidopsis / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism; D035683:MicroRNAs / Q000378:metabolism*; D018613:Microscopy, Confocal; D008954:Models, Biological; D010937:Plant Growth Regulators / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development*; D058526:Plant Vascular Bundle / Q000254:growth & development*; D015398:Signal Transduction / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D018398:Homeodomain Proteins; D035683:MicroRNAs; C114647:PHB protein, Arabidopsis; D010937:Plant Growth Regulators; C410510:SHORT ROOT protein, Arabidopsis; D014157:Transcription Factors
keywords: mathematical modeling; plant development