Shoot apex-derived CLE46 peptide signal spatiotemporally restricts root regeneration in Arabidopsis.

Plants have evolved sophisticated cell-to-cell signaling systems to adapt to environmental stimuli. In response to the environmental stimuli, signals are transmitted to distant areas within the plant by mobile molecules such as plant hormones, nutrients, and peptides. Various CLAVATA3/ESR-related (CLE) peptides play pivotal roles in developmental regulation and stress-response processes. Although CLE46 peptide exhibits high amino acid sequence similarity in the conserved CLE domain with vascular meristem-regulating CLE41 and CLE44, the biological function of CLE46 remains unknown. Here, we investigated the biological role of CLE46 peptide in Arabidopsis thaliana. Spatial expression analysis revealed that CLE46 promoter-β-glucuronidase (GUS) activity is restricted to the shoot apex of young seedlings. However, the cle46 loss-of-function mutant showed no developmental defect under normal conditions. We also found transient CLE46 promoter-GUS activity at the wound site of leaves following petiole excision. The cle46 mutant exhibited enhanced root regeneration at the cut end of leaves. To further investigate the role of CLE46 in root regeneration, we employed a hypocotyl excision-induced system, in which CLE46-GUS activity did not appear at the wound site. In hypocotyl-excised seedlings, CLE46-GUS activity in the shoot apex was decreased prior to root regeneration. Root regeneration rate was higher in the cle46 mutant than wild-type. The root regeneration phenotype of cle46 was rescued not only by the genetic complementation of CLE46 sequence but by the exogenous application of the synthetic CLE46 peptide. These results suggest that CLE46 expressed in the shoot apex may repress root regeneration in the lower part of the tissue as a shoot apex-derived signal.