Involvement of Populus CLEL peptides in root development

Hello everyone, I am very glad to share an interesting study from our research group with you. This paper was published in Tree Physiology on July 9, 2019.

Cell-to-cell signaling mediated by small secreted peptide ligands and their relevant receptor-like kinases (RLKs) is critical for the growth and development of plants. As one of the major groups of small post-translationally modified peptides, the CLV3/EMBRYO SURROUNDING REGIONRELATED (CLE)-like (CLEL) peptide family has been reported to regulate root growth, lateral root development and plant gravitropic responses in Arabidopsis thaliana. 

Populus, as a model system for tree and woody perennial plant biology, is widely employed to unravel the molecular mechanisms of tree growth and development. Our knowledge of small post-translationally modified peptides in Populus has been focused on the CLE gene family, particularly the TDIF genes. Unlike CLE, our knowledge about CLEL genes in Populus remains limited.

In this study, we tried to identify P. trichocarpa CLELs (PtrCLELs) by a genome-wide bioinformatics analysis, to investigate their global expression patterns based on both in silico data and quantitative real-time reverse transcription PCR (qRT-PCR) (Figure 1) and to analyze their potential roles in root development by artificially synthesizing the corresponding CLEL peptides for in vitro application in both A. thaliana and Populus (Figure 2,3). 

Figure 1. Expression analysis of PtrCLEL genes.

Figure 2. Root morphology of PtrCLEL peptide-treated P. deltoides

germinating seeds on the vertical plates.

Figure 3. Root tip sections of wild-type and PtrCLEL10a/b-treated

717 cuttings cultured on MS medium

Our study suggested that PtrCLEL and AtCLEL genes encode proteins with similar protein structures, sequences of peptide motif and peptide activities on developing roots. The activities of PtrCLEL peptides in root development were species-dependent. This study provides important clues about different effects of CLEL peptides in root development in woody species.

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