Abstract：
Legume symbiotic nitrogen fixation (SNF) is suppressed by inorganic nitrogen (N) in the soil. High N inhibition of nitrogenase activity is associated with the deprivation of carbon allocation and metabolism in nodules. However, the underlying molecular mechanisms remain unclear. Here, we identify GmCIN1 which encodes a cytosolic invertase, as a gateway for the N-tuning of sucrose utilization in nodules. GmCIN1 is enriched in mature soybean nodules and its expression is regulated by nitrogen status. The knockout of GmCIN1 using genome editing partially mimics the inhibitory effects of N on nitrogenase activity and sugar content and the impact of high N on nodule transcriptomes. This indicates that GmCIN1 partially mediates the high N inhibition of nodule activity. Moreover, ChIP-qPCR and EMSA reveal that SNAP1/2 transcription factors directly bind to the GmCIN1 promoter. In addition, SNAP1/2 may be involved in the repression of GmCIN1 expression in mature nodules at high N concentrations. Our findings provide insights into the involvement of the transcriptional tuning of carbon (C) metabolism genes by N-signaling modulators in the N-induced inhibition of nitrogenase activity.
摘要：
豆类共生固氮（SNF）被土壤中的无机氮抑制。氮对固氮酶活性的高抑制作用与结节中碳分配和代谢的剥夺有关。然而,潜在的分子机制尚不清楚.这里,我们鉴定了编码细胞溶质转化酶的GmCIN1，作为根瘤中蔗糖利用的N调整的门户。GmCIN1在成熟大豆根瘤中富集，其表达受氮状态调控。使用基因组编辑敲除GmCIN1部分模拟了N对固氮酶活性和糖含量的抑制作用以及高N对根瘤转录组的影响。这表明GmCIN1部分介导了结节活性的高N抑制。此外，ChIP-qPCR和EMSA揭示SNAP1/2转录因子直接结合GmCIN1启动子。此外,SNAP1/2可能参与高N浓度下成熟结节中GmCIN1表达的抑制。我们的发现提供了有关N信号调节剂在N诱导的固氮酶活性抑制中参与C代谢基因转录调节的见解。
