背景回顾：CLAVATA3/EMBRYO SURROUNDING REGION-related (CLE) peptides are a class of small molecules involved in plant growth and development. 

提出问题：Although radish (Raphanus sativus) is an important root vegetable crop worldwide, the functions of CLE peptides in its taproot formation remain elusive. 

结果1-CLE22a表达模式：Here, a total of 48 RsCLE genes were identified from the radish genome. RNA in situ hybridization showed that RsCLE22a gene was highly expressed in the vascular cambium. 

结果2-CLE22a基因功能：Overexpression of RsCLE22a inhibited root growth by impairing stem cell proliferation in Arabidopsis, and radish plants with exogenous supplementation of RsCLE22 peptide (CLE22p) showed a similar phenotype. The vascular cambial activity was increased in RsCLE22a-silenced plants. 

结果3-CLE22a-生长素信号：Transcriptome analysis revealed that CLE22p altered the expression of several genes involved in meristem development and hormone signal transduction in radish. Immunolocalization results showed that CLE22p increased auxin accumulation in vascular cambium. 

结果4-WOX4-CLE22a：Yeast one-hybrid and dual-luciferase assays showed that the WUSCHEL-RELATED HOMEOBOX 4 (RsWOX4) binds to RsCLE22a promoter and activates its transcription. The expression level of RsWOX4 was related to vascular cambial activity and was regulated by auxin. 

结论：Furthermore, a RsCLE22a–RsWOX4 module is proposed to regulate taproot vascular cambium activity through an auxin signaling-related pathway in radish. These findings provide novel insights into the regulation of root growth in a horticultural crop.

Hypothetical model for the regulation of vascular cambium activity by the RsCLE22a–RsWOX4 negative feedback loop in radish taproots.

CLE多肽是一类小分子，参与植物的生长和发育。尽管萝卜是全球范围内重要的块根类蔬菜作物，但是CLE多肽在萝卜主根形成中的作用还不清楚。本文中，作者在萝卜基因组中共鉴定了48个RsCLE基因。RNA原位杂交显示，RsCLE22a在维管形成层中高表达。在拟南芥中过表达RsCLE22a基因会通过损害干细胞的增殖，从而抑制根生长；对萝卜外施RsCLE22多肽（CLE22p）表现出类似的表型。RsCLE22a沉默植株中，维管形成层活性增加。转录组分析显示，CLE22p改变了萝卜中与分生组织发育和激素信号转导相关基因的表达。免疫定位显示CLE22p增加了维管形成层中的生长素积累。酵母单杂和双荧光素酶试验表明，RsWOX4能够直接结合到RsCLE22a基因的启动子上，并激活后者的表达。RsWOX4的表达水平与维管形成层活性相关，并且受到生长素的调节。综上，作者提出RsCLE22a–RsWOX4模块通过一个生长素信号转导相关的通路，作用于萝卜主根中维管形成层活性的调控。本文的研究结果为园艺作物的根生长调控提供了新的视野。

** 柳李旺 **