The precise control of receptor levels is crucial for initiating cellular signaling transduction in response to specific ligands; however, such mechanisms regulating nodulation factor (NF) receptor (NFR)-mediated perception of NFs to establish symbiosis remain unclear. In this study, we unveil the pivotal role of the NFR-interacting RING-type E3 ligase 1 (NIRE1) in regulating NFR1/NFR5 homeostasis to optimize rhizobial infection and nodule development in . We demonstrated that NIRE1 has a dual function in this regulatory process. It associates with both NFR1 and NFR5, facilitating their degradation through K48-linked polyubiquitination before rhizobial inoculation. However, following rhizobial inoculation, NFR1 phosphorylates NIRE1 at a conserved residue, Tyr-109, inducing a functional switch in NIRE1, which enables NIRE1 to mediate K63-linked polyubiquitination, thereby stabilizing NFR1/NFR5 in infected root cells. The introduction of phospho-dead NIRE1 leads to delayed nodule development, underscoring the significance of phosphorylation at Tyr-109 in orchestrating symbiotic processes. Conversely, expression of the phospho-mimic NIRE1 results in the formation of spontaneous nodules in , further emphasizing the critical role of the phosphorylation-dependent functional switch in NIRE1. In summary, these findings uncover a fine-tuned symbiotic mechanism that a single E3 ligase could undergo a phosphorylation-dependent functional switch to dynamically and precisely regulate NF receptor protein levels.

中文翻译：

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豆科植物结瘤期间通过磷酸化介导的 RING 型 E3 连接酶功能开关动态调节结瘤因子受体水平


受体水平的精确控制对于启动响应特定配体的细胞信号转导至关重要；然而，这种调节结瘤因子（NF）受体（NFR）介导的 NF 感知以建立共生的机制仍不清楚。在这项研究中，我们揭示了 NFR 相互作用的 RING 型 E3 连接酶 1 (NIRE1) 在调节 NFR1/NFR5 稳态以优化根瘤菌感染和根瘤发育中的关键作用。我们证明了 NIRE1 在此调节过程中具有双重功能。它与 NFR1 和 NFR5 结合，在根瘤菌接种前通过 K48 连接的多泛素化促进它们的降解。然而，在根瘤菌接种后，NFR1 在保守残基 Tyr-109 处磷酸化 NIRE1，诱导 NIRE1 中的功能开关，使 NIRE1 能够介导 K63 连接的多聚泛素化，从而稳定受感染根细胞中的 NFR1/NFR5。磷酸化死亡 NIRE1 的引入导致根瘤发育延迟，强调了 Tyr-109 磷酸化在协调共生过程中的重要性。相反，磷酸化模拟 NIRE1 的表达导致自发结节的形成，进一步强调了 NIRE1 中磷酸化依赖性功能开关的关键作用。总之，这些发现揭示了一种微调的共生机制，即单个 E3 连接酶可以经历磷酸化依赖性功能转换，以动态、精确地调节 NF 受体蛋白水平。