Root-specific CLE3 expression is required for WRKY33 activation in Arabidopsis shoots

Plant Mol Biol. 2022 Feb;108(3):225-239. doi: 10.1007/s11103-021-01234-9. Epub 2022 Jan 17.

Abstract

This study focused on the role of CLE1-7 peptides as defense mediators, and showed that root-expressed CLE3 functions as a systemic signal to regulate defense-related gene expression in shoots. In the natural environment, plants employ diverse signaling molecules including peptides to defend themselves against various pathogen attacks. In this study, we investigated whether CLAVATA3/EMBRYO SURROUNDING REGION-RELATED (CLE) genes (CLE1-7) respond to biotic stimuli. CLE3 showed significant up-regulation upon treatment with flg22, Pep2, and salicylic acid (SA). Quantitative real-time PCR (qRT-PCR) analysis revealed that CLE3 expression is regulated by the NON-EXPRESSOR OF PR GENES1 (NPR1)-dependent SA signaling and flg22-FLAGELLIN-SENSITIVE 2 (FLS2) signaling pathways. We demonstrated that SA-induced up-regulation of CLE3 in roots was required for activation of WRKY33, a gene involved in the regulation of systemic acquired resistance (SAR), in shoots, suggesting that CLE3 functions as a root-derived signal that regulates the expression of defense-related genes in shoots. Microarray analysis of transgenic Arabidopsis lines overexpressing CLE3 under the control of a β-estradiol-inducible promoter revealed that root-confined CLE3 overexpression affected gene expression in both roots and shoots. Comparison of CLE2- and CLE3-induced genes indicated that CLE2 and CLE3 peptides target a few common but largely distinct downstream genes. These results suggest that root-derived CLE3 is involved in the regulation of systemic rather than local immune responses. Our study also sheds light on the potential role of CLE peptides in long-distance regulation of plant immunity.

Keywords: CLE peptide; Defense responses; Salicylic acid; Systemic response; WRKY; flg22.

MeSH terms

  • Arabidopsis / drug effects
  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Down-Regulation
  • Estradiol / pharmacology
  • Gene Expression Regulation, Developmental / drug effects
  • Gene Expression Regulation, Developmental / physiology
  • Gene Expression Regulation, Plant / drug effects
  • Gene Expression Regulation, Plant / physiology*
  • Intercellular Signaling Peptides and Proteins
  • Plant Roots / genetics
  • Plant Roots / metabolism*
  • Plant Shoots / genetics
  • Plant Shoots / metabolism*
  • Plants, Genetically Modified
  • Salicylic Acid / pharmacology
  • Seedlings / growth & development
  • Seedlings / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Up-Regulation

Substances

  • Arabidopsis Proteins
  • Intercellular Signaling Peptides and Proteins
  • Transcription Factors
  • WRKY33 protein, Arabidopsis
  • Estradiol
  • Salicylic Acid