The CEP5 Peptide Promotes Abiotic Stress Tolerance, As Revealed by Quantitative Proteomics, and Attenuates the AUX/IAA Equilibrium in Arabidopsis

The proteome and phosphoproteome of CEP5 overexpressing Arabidopsis seedlings have been determined. This revealed that CEP5 impacts abiotic stress-related processes. Subsequent genetic, physiological, biochemical, and pharmacological results demonstrated that CEP5-mediated signaling is relevant for osmotic and drought stress tolerance in Arabidopsis. Furthermore, CEP5 specifically counteracts auxin effects by stabilizing AUX/IAA transcriptional repressors. [Display omitted] Highlights •Quantitative Arabidopsis (phospho)proteomes of C-TERMINALLY ENCODED PEPTIDE 5 (CEP5).•CEP5 impacts abiotic stress-related processes and counteracts auxin effects.•CEP5 signaling stabilizes AUX/IAA transcriptional repressors.•Novel peptide-dependent control mechanism that tunes auxin signaling. Peptides derived from non-functional precursors play important roles in various developmental processes, but also in (a)biotic stress signaling. Our (phospho)proteome-wide analyses of C-TERMINALLY ENCODED PEPTIDE 5 (CEP5)-mediated changes revealed an impact on abiotic stress-related processes. Drought has a dramatic impact on plant growth, development and reproduction, and the plant hormone auxin plays a role in drought responses. Our genetic, physiological, biochemical, and pharmacological results demonstrated that CEP5-mediated signaling is relevant for osmotic and drought stress tolerance in Arabidopsis, and that CEP5 specifically counteracts auxin effects. Specifically, we found that CEP5 signaling stabilizes AUX/IAA transcriptional repressors, suggesting the existence of a novel peptide-dependent control mechanism that tunes auxin signaling. These observations align with the recently described role of AUX/IAAs in stress tolerance and provide a novel role for CEP5 in osmotic and drought stress tolerance.