title: Fate map of Medicago truncatula root nodules.
abstract: Legume root nodules are induced by N-fixing rhizobium bacteria that are hosted in an intracellular manner. These nodules are formed by reprogramming differentiated root cells. The model legume Medicago truncatula forms indeterminate nodules with a meristem at their apex. This organ grows by the activity of the meristem that adds cells to the different nodule tissues. In Medicago sativa it has been shown that the nodule meristem is derived from the root middle cortex. During nodule initiation, inner cortical cells and pericycle cells are also mitotically activated. However, whether and how these cells contribute to the mature nodule has not been studied. Here, we produce a nodule fate map that precisely describes the origin of the different nodule tissues based on sequential longitudinal sections and on the use of marker genes that allow the distinction of cells originating from different root tissues. We show that nodule meristem originates from the third cortical layer, while several cell layers of the base of the nodule are directly formed from cells of the inner cortical layers, root endodermis and pericycle. The latter two differentiate into the uninfected tissues that are located at the base of the mature nodule, whereas the cells derived from the inner cortical cell layers form about eight cell layers of infected cells. This nodule fate map has then been used to re-analyse several mutant nodule phenotypes. This showed, among other things, that intracellular release of rhizobia in primordium cells and meristem daughter cells are regulated in a different manner.
authors.affiliation: Department of Plant Sciences, Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, Wageningen 6708 PB, The Netherlands.
authors.forename: Ting Ting
authors.initials: TT
authors.lastname: Xiao
authors.affiliation: Department of Plant Sciences, Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, Wageningen 6708 PB, The Netherlands.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schilderink
authors.affiliation: Department of Plant Sciences, Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, Wageningen 6708 PB, The Netherlands.
authors.forename: Sjef
authors.initials: S
authors.lastname: Moling
authors.affiliation: Department of Plant Sciences, Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, Wageningen 6708 PB, The Netherlands Department of Systems Biophysics, FOM institute AMOLF, Science Park 104, Amsterdam 1098 XG, The Netherlands.
authors.forename: Eva E
authors.initials: EE
authors.lastname: Deinum
authors.affiliation: Institute of Biochemistry, Biological Research Centre, Hungarian Academy of Sciences, Szeged 6726, Hungary.
authors.forename: Eva
authors.initials: E
authors.lastname: Kondorosi
authors.affiliation: Department of Plant Sciences, Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, Wageningen 6708 PB, The Netherlands.
authors.forename: Henk
authors.initials: H
authors.lastname: Franssen
authors.affiliation: Department of Plant Sciences, Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, Wageningen 6708 PB, The Netherlands.
authors.forename: Olga
authors.initials: O
authors.lastname: Kulikova
authors.affiliation: INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan F-31326, France CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan F-31326, France.
authors.forename: Andreas
authors.initials: A
authors.lastname: Niebel
authors.affiliation: Department of Plant Sciences, Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, Wageningen 6708 PB, The Netherlands College of Science, King Saud University, Post Office Box 2455, Riyadh 11451, Saudi Arabia ton.bisseling@wur.nl.
authors.forename: Ton
authors.initials: T
authors.lastname: Bisseling
mesh_terms: D002454:Cell Differentiation / Q000502:physiology; D019070:Cell Lineage / Q000502:physiology*; D003198:Computer Simulation; D005819:Genetic Markers / Q000235:genetics; D006651:Histocytochemistry; D046913:Medicago truncatula / Q000166:cytology* / Q000382:microbiology; D018519:Meristem / Q000166:cytology* / Q000502:physiology; D009024:Morphogenesis / Q000502:physiology*; D053204:Root Nodules, Plant / Q000166:cytology* / Q000382:microbiology
chemical_list: D005819:Genetic Markers
keywords: Endodermis; Indeterminate root nodule; Inner cortex; Medicago; Nodule meristem; Nodule primordium