The MtDMI2-MtPUB2 Negative Feedback Loop Plays a Role in Nodulation Homeostasis
The MtDMI2-MtPUB2 Negative Feedback Loop Plays a Role in Nodulation Homeostasis
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MtDMI2-MtPUB2 负反馈环在结瘤稳态中发挥作用
DOI：
10.1104/pp.17.01587
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发表时间：
2018-04-01
期刊：
影响因子：
7.4
通讯作者：
Dong, Jiangli
中科院分区：
文献类型：
--
作者：
Liu, Jiaxing;Deng, Jie;Dong, Jiangli
不进行感染2（MtDMI 2）是蒺藜苜蓿/苜蓿中华根瘤菌共生途径中信号转导所需的富含Leu的重复类型受体激酶。然而，MtDMI 2参与凝血稳态的机制知之甚少。在这项研究中，我们确定了MtPUB 2-一种新的植物U盒（PUB）型E3连接酶-并表明它与MtDMI 2相互作用。显示MtDMI 2和MtPUB 2积累在各种组织中相似。与用空载体转化的对照植物相比，其中MtPUB 2通过RNAi沉默的植物（MtPUB 2-RNAi植物）的根表现出受损的感染丝、更少的结节和更短的初生根长度。使用液相色谱-串联质谱法，我们表明，MtDMI 2磷酸化MtPUB 2在Ser-316，Ser-421，和Thr-488残基。当用模拟磷酸化状态的MtPUB 2（S421 D）转化MtPUB 2-RNAi植物时，MtDMI 2被MtPUB 2（S421 D）持续泛素化并降解，导致比在MtPUB 2/MtPUB 2 RNAi补充植物中观察到的更少的结节。而MtPUB 2（S421 A）/MtPUB 2-RNAi互补植株则没有表现出MtPUB 2泛素化活性，其泛素化表型与空载体转化的MtPUB 2-RNAi植株相似。进一步的研究表明，这些蛋白质形成了猎物（MtDMI 2）-捕食者（MtPUB 2）类型的负反馈环。我们的研究结果表明，MtDMI 2-MtPUB 2负反馈回路，它显示通过MtNIN与长距离自动调节的排尿串扰，在排尿稳态中起着重要作用。
DOES NOT MAKE INFECTION 2 (MtDMI2) is a Leu rich repeat-type receptor kinase required for signal transduction in the Medicago truncatula/Sinorhizobium meliloti symbiosis pathway. However, the mechanisms through which MtDMI2 participates in nodulation homeostasis are poorly understood. In this study, we identified MtPUB2-a novel plant U-box (PUB)-type E3 ligase -and showed that it interacts with MtDMI2. MtDMI2 and MtPUB2 accumulation were shown to be similar in various tissues. Roots of plants in which MtPUB2 was silenced by RNAi (MtPUB2-RNAi plants) exhibited impaired infection threads, fewer nodules, and shorter primary root lengths compared to those of control plants transformed with empty vector. Using liquid chromatography-tandem mass spectrometry, we showed that MtDMI2 phosphorylates MtPUB2 at Ser-316, Ser-421, and Thr-488 residues. When MtPUB2-RNAi plants were transformed with MtPUB2(S421D), which mimics the phosphorylated state, MtDMI2 was persistently ubiquitinated and degraded by MtPUB2(S421D), resulting in fewer nodules than observed in MtPUB2/MtPUB2RNAi-complemented plants. However, MtPUB2(S421A)/MtPUB2-RNAi-complemented plants showed no MtPUB2 ubiquitination activity, and their nodulation phenotype was similar to that of MtPUB2-RNAi plants transformed with empty vector. Further studies demonstrated that these proteins form a negative feedback loop of the prey (MtDMI2)-predator (MtPUB2) type. Our results suggest that the MtDMI2-MtPUB2 negative feedback loop, which displays crosstalk with the long-distance autoregulation of nodulation via MtNIN, plays an important role in nodulation homeostasis.