Sterols regulate endocytic pathways during flg22-induced defense responses in Arabidopsis

Development. 2018 Oct 1;145(19):dev165688. doi: 10.1242/dev.165688.

Abstract

The plant transmembrane receptor kinase FLAGELLIN SENSING 2 (FLS2) is crucial for innate immunity. Although previous studies have reported FLS2-mediated signal transduction and endocytosis via the clathrin-mediated pathway, whether additional endocytic pathways affect FLS2-mediated defense responses remains unclear. Here, we show that the Arabidopsis thaliana sterol-deficient mutant steroid methyltransferase 1 displays defects in immune responses induced by the flagellin-derived peptide flg22. Variable-angle total internal reflection fluorescence microscopy (VA-TIRFM) coupled with single-particle tracking showed that the spatiotemporal dynamics of FLS2-GFP changed on a millisecond time scale and that the FLS2-GFP dwell time at the plasma membrane increased in cells treated with a sterol-extracting reagent when compared with untreated counterparts. We further demonstrate that flg22-induced FLS2 clustering and endocytosis involves the sterol-associated endocytic pathway, which is distinct from the clathrin-mediated pathway. Moreover, flg22 enhanced the colocalization of FLS2-GFP with the membrane microdomain marker Flot 1-mCherry and FLS2 endocytosis via the sterol-associated pathway. This indicates that plants may respond to pathogen attacks by regulating two different endocytic pathways. Taken together, our results suggest the key role of sterol homeostasis in flg22-induced plant defense responses.

Keywords: Endocytosis; FLS2; Plant immunity; Spatiotemporal dynamics; Sterols; VA-TIRFM.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / cytology*
  • Arabidopsis / drug effects
  • Arabidopsis / immunology*
  • Arabidopsis Proteins / metabolism
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Clathrin / metabolism
  • Endocytosis* / drug effects
  • Flagellin / pharmacology*
  • Green Fluorescent Proteins / metabolism
  • Methyltransferases / metabolism
  • Mutation / genetics
  • Plant Epidermis / cytology
  • Plant Immunity / drug effects
  • Plants, Genetically Modified
  • Protein Aggregates
  • Protein Kinases / metabolism
  • Protein Multimerization
  • Sterols / metabolism*

Substances

  • Arabidopsis Proteins
  • Clathrin
  • Protein Aggregates
  • Sterols
  • Flagellin
  • Green Fluorescent Proteins
  • Methyltransferases
  • SMT1 protein, Arabidopsis
  • Protein Kinases
  • FLS2 protein, Arabidopsis