背景回顾：Optimal root system architecture is beneficial for water-fertilizer use efficiency, stress tolerance and yield improvement of crops. 

提出问题：However, because of the complexity of root traits and difficulty in phenotyping deep roots, the study on mechanisms of root development is rarely reported in wheat (Triticum aestivum L.). 

主要发现：In this study, we identified that the LBD(LATERAL ORGAN BOUNDARIES DOMAIN) gene TaMOR (MORE ROOT in wheat) determines wheat crown root initiation. 

结果1-mor突变体表型：The mor mutants exhibited less or even no crown root, dwarfism, less grain number, and lodging caused by few roots. The observation of cross sections showed that crown root initiation is inhibited in the mor mutants. 

结果2-TaMOR-ARF5-PIN2：Molecular assays revealed that TaMOR interacts with the auxin response factor ARF5 to directly induce the expression of the auxin transporter gene PIN2 (PIN-FORMED 2) in the root base to regulate crown root initiation. 

结果3-MITE插入影响TaMOR-B表达：In addition, a 159-bp MITE (miniature inverted-repeat transposable element) insertion causing DNA methylation and lower expression of TaMOR-B was identified in TaMOR-B promoter, which is associated with lower root dry weight and shorter plant height. 

结论：The results bring new light into regulation mechanisms of crown root initiation and offer a new target for the improvement of root system architecture in wheat.

 摘 要 

最优根系统结构对于作物的水肥利用效率、胁迫耐受性以及产量提升是非常有益的。但是，由于根性状的复杂性以及在深根表型鉴定方面的困难，对于小麦中的根发育机制研究还很局限。本文中，作者鉴定到了一个LBD基因TaMOR，该基因作用于小麦冠根的起始。mor突变体存在冠根减少甚至没有冠根的情况，另外还存在植株矮小、籽粒减少等现象，以及由于根系较少所导致的植株倒伏现象。切片观察显示mor突变体的冠根起始被抑制。分子试验显示TaMOR能够与生长素响应因子ARF5发生互作，直接诱导生长素转运基因PIN2在根基部的表达，从而调控冠根的起始。另外，TaMOR-B基因启动子区域上一段159bp的MITE插入导致该区域发生甲基化，导致TaMOR-B基因的表达水平较低，这与较低的根干重和较矮的株高有关。本文的研究结果揭示了一个小麦中冠根起始的调控机制，为未来小麦的根系统结构改良提供了新的候选靶点。