CLE Signaling Systems During Plant Development and Nematode Infection

Plants contain numerous CLAVATA3 (CLV3)/EMBRYO SURROUNDING REGION (ESR) (CLE) genes encoding small secreted peptide hormones that function in a variety of developmental and physiological processes. The first known Arabidopsis CLE gene was originally discovered through the analysis of clv3 mutants, which exhibit fasciated stems and an increased number of floral organs. In total, 32 CLE genes have been identified in Arabidopsis. Amongst these are CLV3 and CLE40, which repress the expression of homeobox-containing genes WUSCHEL (WUS) and WUSCHEL-related homeobox 5 (WOX5) to control shoot apical meristem (SAM) and root columella initial cell activity, respectively. Interestingly, the CLE signaling pathway appears to be conserved amongst plants. In this review, we discuss the latest research uncovering the diverse functions and activities of CLE peptides in plants; especially during shoot, root and vascular development. In addition, we discuss the important role of CLE peptides during infection by phytoparasitic nematodes. Understanding the molecular properties of CLE peptides and their modes of action will provide further insight into plant cell-cell communication, which could also be applied to manipulate plant-nematode interactions.