CEP13, CEP14, and CEP15 peptides inhibit root development and de novo shoot regeneration in Arabidopsis

C-TERMINALLY ENCODED PEPTIDE (CEP) peptides are essential for plant developmental and adaptive responses, but their biological roles, particularly those of group II CEPs, are not fully understood. Here, we determined that group II CEP peptides, CEP13, CEP14, and CEP15, function redundantly as important regulators in root development and adventitious shoot regeneration. Application of these peptides significantly inhibited primary root elongation, lateral root formation, and de novo shoot regeneration. In contrast, the cep13, cep14, and cep15 single mutants, as well as their double and triple mutants, exhibited enhanced primary root length, and increased numbers of lateral roots and adventitious shoots. The group II CEP peptide-mediated inhibition of root growth requires the receptor-like kinase CEP RECEPTOR 1 (CEPR1), while CEP14- and CEP13/CEP15-mediated inhibition of shoot regeneration depends on CEPR1 and CEPR1/CEPR2, respectively. We further found that group II CEP peptides are likely affect auxin biosynthesis and its polar transport, thereby modulating primary and lateral root development. Collectively, our results reveal that CEP13, CEP14, and CEP15 peptides regulate primary root length, lateral root formation, and de novo shoot regeneration through a CEPR-dependent mechanism.