Genome-Wide Identification and Functional Analysis of CLAVATA3/EMBRYO SURROUNDING REGION-RELATED (CLE) in Three Populus Species

Intercellular communication mediated by CLAVATA3/EMBRYO SURROUNDING REGION-RELATED (CLE) peptides and their receptors is crucial for plant development and environmental adaptation. In this study, 45 and 89 <i>CLEs</i> were identified in <i>Populus tomentosa</i> and <i>Populus alba</i> × <i>Populus glandulosa</i>, respectively, and, together with the 52 <i>CLEs</i> in <i>Populus trichocarpa</i>, the chromosome localization, gene and protein characteristics, collinearity and gene duplication events, cis-acting regulatory elements in promoters and evolutionary relationships of <i>CLEs</i> in these three poplar species were analyzed. The <i>CLEs</i> of three poplar species were divided into four subfamilies. Among them, the <i>CLEs</i> in subfamilies I, II and IV were A-type <i>CLEs</i>, while those in subfamily III were B-type <i>CLEs</i>. During the evolutionary process of poplar, the selection pressure faced by whole-genome duplication or segmental duplication was purifying selection, and the duplication events led to the expansion of the <i>CLE</i> family in poplar. The exogenous addition of a certain concentration of poplar CLE13 peptides inhibits the root growth of <i>Arabidopsis thaliana</i> and poplar and simultaneously reduces the expression levels of <i>ARFs</i> and <i>LBDs</i> in the roots. In addition, drought stress induces the expression of <i>PtrCLE13A</i>. The overexpression of <i>preCLE13A</i> significantly enhances the osmotic and drought tolerance in <i>Populus tomentosa</i>. These results have provided valuable information for further research on the molecular mechanisms of CLE peptide signaling pathways in the woody model plant poplar regarding plant growth and stress resistance.