Substantial progress has been made in the understanding of early stages of the symbiotic interaction between legume plants and rhizobium bacteria. Those include the specific recognition of symbiotic partners, the initiation of bacterial infection in root hair cells, and the inception of a specific organ in the root cortex, the nodule. Increasingly complex regulatory networks have been uncovered in which cytokinin (CK) phytohormones play essential roles in different aspects of early symbiotic stages. Intriguingly, these roles can be either positive or negative, cell autonomous or non-cell autonomous, and vary, depending on time, root tissues, and possibly legume species. Recent developments on CK symbiotic functions and interconnections with other signaling pathways during nodule initiation are the focus of this review.

在了解豆类植物与根瘤菌之间的共生相互作用的早期阶段已经取得了实质性进展。这些措施包括对共生伴侣的特异性识别，在根毛细胞中细菌感染的起始以及在根皮层中特定器官（结节）的开始。已经发现越来越复杂的调节网络，其中细胞分裂素（CK）植物激素在早期共生阶段的不同方面起着至关重要的作用。有趣的是，这些作用可以是阳性或阴性，细胞自主或非细胞自主，并根据时间，根组织以及可能的豆科植物种类而变化。结节启动过程中CK共生功能以及与其他信号通路的相互联系的最新进展是本综述的重点。