Cleavage of the SYMBIOSIS RECEPTOR-LIKE KINASE Ectodomain Promotes Complex Formation with Nod Factor Receptor 5
Cleavage of the SYMBIOSIS RECEPTOR-LIKE KINASE Ectodomain Promotes Complex Formation with Nod Factor Receptor 5
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DOI：
10.1016/j.cub.2013.12.053
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发表时间：
2014-02-17
期刊：
影响因子：
9.2
通讯作者：
Parniske, Martin
中科院分区：
文献类型：
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作者：
Antolin-Llovera, Meritxell;Ried, Martina K.;Parniske, Martin
植物与真菌和细菌形成根部共生，以改善其营养供应。共生受体样激酶 (SYMRK) 是获取磷酸盐的丛枝菌根以及豆科植物 [1] 和放线菌植物 [2, 3] 固氮根瘤共生所必需的，但其确切功能完全不清楚。在这里，我们表明，SYMRK 的胞质外区域包含三个富含亮氨酸的重复序列 (LRR) 和一个与非洲爪蟾碳水化合物结合蛋白相关的马来素样结构域 (MLD) [4]，在没有共生刺激的情况下被切割以释放 MLD。 MLD 释放需要连接 MLD 和 LRR 的保守序列基序 -GDPC。我们发现 Nod 因子受体 5 (NFR5) [5-8] 与 MLD 释放后保留的 SYMRK 版本形成复合物 (SYMRK-Delta MLD)。 SYMRK-Delta MLD 在 NFR5 相互作用方面胜过全长 SYMRK，表明 MLD 对复合物形成有负面干扰。 SYMRK-Delta MLD 的含量低于 MLD，表明 MLD 释放后会快速降解。整个胞质外区域的缺失增加了蛋白质丰度，表明 LRR 区域促进了降解。奇怪的是，这种删除导致了过度的感染线形成，凸显了 SYMRK 胞外域微调调节的重要性。
Plants form root symbioses with fungi and bacteria to improve their nutrient supply. SYMBIOSIS RECEPTOR-LIKE KINASE (SYMRK) is required for phosphate-acquiring arbuscular mycorrhiza, as well as for the nitrogen-fixing root nodule symbiosis of legumes [1] and actinorhizal plants [2, 3], but its precise function was completely unclear. Here we show that the extracytoplasmic region of SYMRK, which comprises three leucine-rich repeats (LRRs) and a malectin-like domain (MLD) related to a carbohydrate-binding protein from Xenopus laevis [4], is cleaved to release the MLD in the absence of symbiotic stimulation. A conserved sequence motif-GDPC-that connects the MLD to the LRRs is required for MLD release. We discovered that Nod factor receptor 5 (NFR5) [5-8] forms a complex with the SYMRK version that remains after MLD release (SYMRK-Delta MLD). SYMRK-Delta MLD outcompeted full-length SYMRK for NFR5 interaction, indicating that the MLD negatively interferes with complex formation. SYMRK-Delta MLD is present at lower amounts than MLD, suggesting rapid degradation after MLD release. A deletion of the entire extracytoplasmic region increased protein abundance, suggesting that the LRR region promotes degradation. Curiously, this deletion led to excessive infection thread formation, highlighting the importance of fine-tuned regulation of SYMRK by its ectodomain.