背景回顾：Propagation through stem cuttings is a popular method world-wide for species such as fruit tree rootstocks and forest trees. Adventitious root (AR) formation from stem cuttings is crucial for effective and successful clonal propagation of apple rootstocks. 

提出问题：Strigolactones (SLs) are newly identified hormones, involved in AR formation. However, the regulatory mechanisms underpinning this process remain elusive. 

主要发现：In this study, weighted gene co-expression network analysis (WGCNA), and rooting assays using stable transgenic apple materials, revealed that MdBRC1 served as a key gene in the inhibition of AR formation by SLs. 

结果1-SMXL7-WRKY6-BRC1：We have demonstrated that MdSMXL7 and MdWRKY6synergistically regulated MdBRC1 expression, depending on the interactions of MdSMXL7 and MdWRKY6 at the protein level downstream of SLs as well as the direct promoter binding on MdBRC1 by MdWRKY6.  

结果2-BRC1-GH3.1：Furthermore, biochemical studies and genetic analysis revealed that MdBRC1 inhibited AR formation by triggering the expression of MdGH3.1 in a transcriptional activation pathway. 

结论：Finally, our study not only proposes a novel component, MdWRKY6, that enables MdSMXL7 to regulate MdBRC1 during the process of SLs-controlled AR formation in apple, but also provides prospective target genes to enhance AR formation capacity using CRISPR technology, particularly in woody plants.

通过植物的茎端插条进行繁殖是全球范围内针对果树砧木和林木等植物的普遍方法。插条上不定根的形成对于苹果砧木的无性繁殖至关重要。独脚金内酯（SL）是一类新的植物激素，参与植物不定根的形成。但是，SL介导植物不定根形成的分子机制并不清楚。本文中，作者通过基因共表达网络分析和稳定转化苹果植株的生根实验，发现MdBRC1作为一个关键基因参与了SLs介导的不定根形成抑制。作者发现MdSMXL7和MdWRKY6协同调控MdBRC1基因的表达，这主要依赖于MdSMXL7和MdWRKY6在蛋白层面的互作以及MdWRKY6直接结合到MdBRC1启动子的能力。此外，生化实验和遗传学分析显示，MdBRC1通过靶向并诱导MdGH3.1基因的表达，从而抑制不定根的形成。综上，本文的研究不仅揭示了MdWRKY6和MdSMXL7通过调控MdBRC1基因的表达参与了SL介导的苹果不定根形成过程，同时也为利用CRISPR技术进行植物尤其是林木的不定根形成能力改良提供了候选靶标。