背景回顾：Crown root morphogenesis is critical for normal growth and nutrition absorption in cereals. In rice, WUSCHEL-RELATED HOMEOBOX11 (WOX11) and CROWN ROOTLESS1 (CRL1) play vital roles in controlling crown root development. 

提出问题：Despite their importance, it remains unclear whether and how the two regulators coordinate crown root formation. 

结果1-CRL1和WOX11结合并激活CKX4：Eletrophoretic mobility shift assays (EMSAs), transient expression and chromatin immunoprecipitation qPCR (ChIP-qPCR) suggested that WOX11 and CRL1 directly bind to OsCKX4 to regulate its expression during crown root development. 

结果2-CRL1和WOX11的协同作用：CRL1 enhances OsCKX4 activation through direct interaction with WOX11 at root emergence and elongation stages. Genetic dissection showed that wox11/crl1 double mutant exhibits a more severe root phenotype. 

结果3-CKX4作用于WOX11和CRL1的下游：OsCKX4 knock-out plants generated by CRISPR/Cas9 exhibited fewer crown roots number and higher cytokinin levels in root meristem. Increased expression of OsCKX4 could partially complement the crown root phenotypes of both crl1 and wox11 mutants. 

结果4-CK与WOX11：Furthermore, cytokinin can promote WOX11 protein accumulation in root meristem. 

结论：Together, these findings show that cytokinin accumulation is tightly regulated by the WOX11-CRL1 complex during crown root elongation by counter-acting on the negative regulatory effects of cytokinin on root development. Importantly, these results reveal an intrinsic link between WOX11 protein accumulation and cytokinin to maintain crown root growth.

A proposed model of WOX11-CRL1 promoting crown root development by maintaining cytokinin homeostasis.

冠根的形态建成对于谷类作物的正常生长和营养吸收至关重要。在水稻中，WOX11和CRL1在控制冠根发育方面发挥重要作用。但是，有关这两个调控子是否存在协同作用，以及如何协同作用于根冠的形成，还不清楚。本文中，作者通过EMSA试验、瞬时表达和ChIP-qPCR试验，发现WOX11和CRL1均可以在冠根发育过程中直接结合OsCKX4基因以调控其表达水平。遗传试验显示wox11/crl1双突变体存在更严重的根缺陷表型。通过CRISPR/Cas9敲除OsCKX4基因会导致冠根数变少、根分生组织中细胞分裂素水平增高。OsCKX4表达的增强可以部分恢复wox11和crl1突变体的冠根缺陷表型。此外，细胞分裂素可以促进WOX11在根分生组织中的积累。综上，本文的研究结果显示冠根伸长过程中，WOX11-CRL1复合物通过对抗细胞分类素对根发育的负调控作用，严格控制细胞分裂素的积累。重要的是，本文的研究结果揭示了一个WOX11蛋白积累和细胞分裂素的内在联系，作用于谷类作物冠根发育的维持。

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