Meristem Activity Regulation by Peptide Hormones

Peptide hormones are small molecules (typically <50 amino acids) that regulate various processes, including meristem activity, growth, and defense responses in plants. They were previously overlooked in favor of nonpeptidic hormones, but have drawn more attention after systemic hormones were discovered in 1991. One of the best-studied groups of peptide hormones is the CLAVATA3/embryo surrounding region-related (CLE) peptides. CLE peptides bind with specific receptor kinases such as CLAVATA1, CLAVATA2, and RECEPTOR-LIKE PROTEIN KINASE 2 and regulate meristem activity. CLE peptides also influence some other key regulators like WUSCHEL, which is essential for maintaining stem cells in meristems. Further, some peptides, such as phytosulfokines (PSKs), Tracheary Element Differentiation Inhibitory Factor (TDIF), and Root Growth Factor (RGF), also play significant roles in regulating meristem function, from cell proliferation to vascular tissue differentiation. The involvement of CLE peptides in nodule formation in legumes further highlights their diverse regulatory impact. This chapter explores the regulation of meristem activity by peptide hormones.