Auxin-Regulated Reversible Inhibition of TMK1 Signaling by MAKR2 Modulates the Dynamics of Root Gravitropism

Curr Biol. 2021 Jan 11;31(1):228-237.e10. doi: 10.1016/j.cub.2020.10.011. Epub 2020 Nov 5.


Plants are able to orient their growth according to gravity, which ultimately controls both shoot and root architecture.1 Gravitropism is a dynamic process whereby gravistimulation induces the asymmetric distribution of the plant hormone auxin, leading to asymmetric growth, organ bending, and subsequent reset of auxin distribution back to the original pre-gravistimulation situation.1-3 Differential auxin accumulation during the gravitropic response depends on the activity of polarly localized PIN-FORMED (PIN) auxin-efflux carriers.1-4 In particular, the timing of this dynamic response is regulated by PIN2,5,6 but the underlying molecular mechanisms are poorly understood. Here, we show that MEMBRANE ASSOCIATED KINASE REGULATOR2 (MAKR2) controls the pace of the root gravitropic response. We found that MAKR2 is required for the PIN2 asymmetry during gravitropism by acting as a negative regulator of the cell-surface signaling mediated by the receptor-like kinase TRANSMEMBRANE KINASE1 (TMK1).2,7-10 Furthermore, we show that the MAKR2 inhibitory effect on TMK1 signaling is antagonized by auxin itself, which triggers rapid MAKR2 membrane dissociation in a TMK1-dependent manner. Our findings suggest that the timing of the root gravitropic response is orchestrated by the reversible inhibition of the TMK1 signaling pathway at the cell surface.

Keywords: MAKR; ROP6; TMK; anionic lipids; auxin; brassinosteroid; gravitropism; receptor-like kinase; root.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Arabidopsis Proteins / antagonists & inhibitors
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Gain of Function Mutation
  • Gravitation
  • Gravitropism / physiology*
  • Indoleacetic Acids / metabolism*
  • Loss of Function Mutation
  • Membrane Proteins / antagonists & inhibitors
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Plant Roots / growth & development*
  • Plants, Genetically Modified
  • Protein Serine-Threonine Kinases / antagonists & inhibitors
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism*
  • Signal Transduction / physiology


  • AT1G64080 protein, Arabidopsis
  • Arabidopsis Proteins
  • Indoleacetic Acids
  • Membrane Proteins
  • PIN2 protein, Arabidopsis
  • AT1G66150 protein, Arabidopsis
  • Protein Serine-Threonine Kinases