The MtDMI2-MtPUB2 Negative Feedback Loop Plays a Role in Nodulation Homeostasis  . Issue 4 (13th February 2018)

• Record Type: Journal Article
• Authors: Liu, Jiaxing; Deng, Jie; Zhu, Fugui; Li, Yuan; Lu, Zheng; Qin, Peibin; Wang, Tao; Dong, Jiangli
• Is Part Of: Plant physiology. Volume 176:Issue 4(2018)
• Page Start: 3003
• Page End: 3026
• Publication Date: 2018-02-13
• Subjects: Plant physiology -- Periodicals; Botany -- Periodicals; Periodicals; Electronic journals; 571.2
• DOI: 10.1104/pp.17.01587
• Languages: English
• ISSNs: 0032-0889

Abstract

Abstract : MtPUB2 and MtDMI2 form a negative feedback loop that regulates nodulation homeostasis in the Medicago truncatula/Sinorhizobium meliloti symbiosis. Abstract: 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 / MtPUB2 -RNAi-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.