Soybean CLE peptides and their CLAVATA-like signaling pathways

Plants coordinate development through complex signaling networks involving many different types of molecules, genes, proteins, and hormones. CLAVATA3-Endosperm Surrounding Region-related (CLE) peptides are one such family of signaling molecules that have roles in general plant development as well during interactions with abiotic and biotic factors. Members of the CLE peptide family have been well studied in the model species, Arabidopsis thaliana; with extensive CLV3, CLE40 and TDIF signaling pathways having been identified. These CLE peptide pathways tend to have three core elements including a CLE peptide, which is perceived by a Receptor-Kinase that regulates a WUSCHEL-like homeobox transcription factor. Such elements are also present in the Autoregulation of Nodulation pathway that controls nodule number during the legume-rhizobia symbiosis. In the soybean genome, 84 CLE peptide-encoding genes are present, although little research outside of nodulation has been undertaken to understand how they modulate growth in the model legume. Understanding CLE peptides may provide novel targets to improve soybean growth and productivity. Moreover, it also represents a unique opportunity to study CLE peptides in the context of beneficial symbiosis with rhizobia and mycorrhizae of which A. thaliana cannot undergo. This chapter reviews the current understanding of CLE peptide signaling in plants, what is currently known about soybean orthologues, and avenues that we can target to improve soybean development using the CLE peptides and their associated molecular networks.