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Key message
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.