Diffusible repression of cytokinin signalling produces endodermal symmetry and passage cells

Nature. 2018 Mar 22;555(7697):529-533. doi: 10.1038/nature25976. Epub 2018 Mar 14.

Abstract

In vascular plants, the root endodermis surrounds the central vasculature as a protective sheath that is analogous to the polarized epithelium in animals, and contains ring-shaped Casparian strips that restrict diffusion. After an initial lag phase, individual endodermal cells suberize in an apparently random fashion to produce 'patchy' suberization that eventually generates a zone of continuous suberin deposition. Casparian strips and suberin lamellae affect paracellular and transcellular transport, respectively. Most angiosperms maintain some isolated cells in an unsuberized state as so-called 'passage cells', which have previously been suggested to enable uptake across an otherwise-impermeable endodermal barrier. Here we demonstrate that these passage cells are late emanations of a meristematic patterning process that reads out the underlying non-radial symmetry of the vasculature. This process is mediated by the non-cell-autonomous repression of cytokinin signalling in the root meristem, and leads to distinct phloem- and xylem-pole-associated endodermal cells. The latter cells can resist abscisic acid-dependent suberization to produce passage cells. Our data further demonstrate that, during meristematic patterning, xylem-pole-associated endodermal cells can dynamically alter passage-cell numbers in response to nutrient status, and that passage cells express transporters and locally affect the expression of transporters in adjacent cortical cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / anatomy & histology*
  • Arabidopsis / cytology*
  • Arabidopsis / growth & development
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / metabolism
  • Body Patterning*
  • Cell Differentiation
  • Cytokinins / metabolism*
  • Diffusion*
  • Endoderm / anatomy & histology
  • Endoderm / cytology*
  • Endoderm / metabolism*
  • Indoleacetic Acids / metabolism
  • Meristem / anatomy & histology
  • Meristem / cytology
  • Meristem / growth & development
  • Meristem / metabolism
  • Plant Cells / metabolism
  • Signal Transduction*

Substances

  • Arabidopsis Proteins
  • Cytokinins
  • Indoleacetic Acids
  • PHO1 protein, Arabidopsis