背景1：During secondary growth, meristematic cells in the cambium can either proliferate to maintain the stem cell population or differentiate into xylem or phloem. The balance between these two developmental trajectories is tightly regulated by many environmental and endogenous cues. 

背景2：Strigolactones (SLs), a class of plant hormones, were previously reported to regulate secondary growth by promoting cambium activity. 

提出问题：However, the underlying molecular mechanisms of SL action in plant secondary growth are not well understood.

研究材料与方法：We performed histological, genetic, and biochemical analyses using genetic materials in Arabidopsis (Arabidopsis thaliana) with altered activity of the transcription factors BRI1-EMS-SUPPRESSOR1 (BES1) or WUSCHEL-related HOMEOBOX4 (WOX4) or lacking MORE AXILLARY SHOOT2 (MAX2), a key positive component in the SL signaling pathway. 

结果1-BES1-WOX4：We found that BES1, a downstream regulator in the SL signaling pathway that promotes shoot branching and xylem differentiation, also inhibits WOX4 expression, a key regulator of cambium cell division in the intercellular TRACHEARY ELEMENT DIFFERENTIATION INHIBITORY FACTOR (TDIF)–TDIF RECEPTOR (TDR) signaling pathway. 

结果2-BES1-TDIF-WOX4：The antagonistic roles of BES1 and WOX4 in the regulation of cambium activity may integrate intercellular TDIF signals to efficiently and bidirectionally modulate cambium cell proliferation and differentiation. 

结论：As both BES1 and WOX4 are widely involved in various endogenous signals and responses to environmental stimuli, these findings may provide insight into the dynamic regulation of cambium development.

 摘 要 

在次生生长过程中，形成层中的分生细胞要么通过增殖来维持干细胞群，或者分化以形成木质部或韧皮部。这两个发育轨迹之间的平衡是由许多环境和内在因素共同调节的。独角金内酯（SLs）是一类植物激素，先前的研究显示SLs能够通过促进形成层活性，调控植物的次生生长。但是，SLs作用于植物次生生长的潜在分子机制还不清楚。本文中，作者通过对拟南芥转录因子BES1或WOX4活性改变以及缺少一个SL信号转导途径关键组分MAX2的遗传材料进行了组织学、遗传学和生物化学的分析。作者发现，SL信号转导途径下游的转录因子BES1能够促进地上部分的分枝以及木质部的分化，同时还能够抑制TDIF-TDR信号转导途径中一个调控形成层分裂的关键因子WOX4的表达。BES1与WOX4在形成层活性调控上的拮抗作用可能整合了胞间的TDIF信号，从而高效的双向调节形成层细胞的增殖和分化。由于BES1和WOX4均广泛参与多个内源信号和对环境刺激的响应，本文的发现可能为深入了解形成层发育的动态调节提供了新的视野。

 通讯作者 

** 王学路 **