摘要Symbiotic root nodules are root lateral organs of plants in which nitrogen-fixing bacteria (rhizobia) convert atmospheric nitrogen to ammonia.The formation and number of nodules in legumes are precisely controlled by a rhizobia-induced signal cascade and host-controlled autoregulation of nodulation (AON).However,how these pathways are integrated and their underlying mechanisms are unclear.Here,we report that microRNA172c (miR172c) activates soybean (Glycine max) Rhizobia-lnduced CLE1 (GmRIC1) and GmRIC2 by removing the transcriptional repression of these genes by Nodule Number Control 1 (NNC1),leading to the activation of the AON pathway.NNC1 interacts with GmNINa,the soybean ortholog of Lotus NODULE INCEPTION (NIN),and hampers its transcriptional activation of GmRIC1 and GmRIC2.Importantly,GmNINa acts as a transcriptional activator of miR172c.Intriguingly,NNC1 can transcriptionally repress miR172c expression,adding a negative feedback loop into the NNC1 regulatory network.Moreover,GmNINa interacts with NNC1 and can relieve the NNC1-mediated repression of miR172c transcription.Thus,the GmNINa-miR172c-NNC1 network is a master switch that coordinately regulates and optimizes NF and AON signaling,supporting the balance between nodulation and AON in soybean.