A Collection of Mutants for CLE-Peptide-Encoding Genes in Arabidopsis Generated by CRISPR/Cas9-Mediated Gene Targeting.

The ligand-receptor-mediated intercellular communication system plays important roles in coordinating developmental and physiological events in multicellular organisms. In plants, CLAVATA3/EMBRYO SURROUNDING REGION (CLE) peptides and their cognate receptors are thought to be involved in various aspects of the plant life cycle. Although the importance of this communication is broadly recognized, most CLE peptides are yet to be functionally characterized. A major problem in research on small signaling peptide-encoding genes is the limited number of loss-of-function mutants available due to their small gene size. CRISPR/Cas9-mediated gene targeting has the potential to overcome this problem, as it can be used to generate targeted mutations in essentially any gene, regardless of size. Here we generated a series of mutants of CLE-peptide-encoding genes. Newly generated clv3 and cle40 mutants reproduced the expected mutant phenotypes in the shoot apical meristem and root meristem, respectively. Our results show that CRISPR/Cas9-mediated gene targeting is a powerful tool for genetic analyses, even of small genes. We also report a novel mutant for CLE44 [which is thought to encode a tracheary elements differentiation inhibitory factor (TDIF)] and show that CLE44 contributes to vascular development. The bioresources presented here will be a powerful tool for further characterization of CLE peptides.