Ubiquitination is a post-translational modification with reversible attachment of the small protein ubiquitin, which is involved in numerous cellular processes including membrane trafficking. For example, ubiquitination of cargo proteins is known to regulate their subcellular dynamics, and plays important roles in plant growth and stress adaptation. However, the regulatory mechanism of the trafficking machinery components remains elusive. Here, we report Arabidopsis trans-Golgi network/early endosome (TGN/EE) localized soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) protein SYP61 as a novel ubiquitination target of a membrane localized ubiquitin ligase ATL31. SYP61 is a key component of membrane trafficking in Arabidopsis. SYP61 was ubiquitinated with K63-linked chain by ATL31 in vitro and in plants. The knockdown mutants of SYP61 were hypersensitive to the disrupted carbon (C)/nitrogen (N)-nutrient stress, suggesting its critical role in plant homeostasis in response to nutrients. We also found the ubiquitination status of SYP61 is affected by C/N-nutrient availability. These results provided possibility that ubiquitination of SNARE protein has important role in plant physiology.

中文翻译：

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TGN / EE SNARE蛋白SYP61遍在蛋白化，是拟南芥中碳/氮养分反应的必需物质

泛素化是翻译后修饰，带有小蛋白泛素的可逆附着，泛素参与许多细胞过程，包括膜运输。例如，已知货物蛋白的泛素化调节其亚细胞动力学，并在植物生长和逆境适应中起重要作用。但是，贩运机器组成部分的监管机制仍然难以捉摸。在这里，我们报告拟南芥反-高尔基网络/早期内体（TGN / EE）本地化可溶性氮-乙基马来酰亚胺敏感因子附着蛋白受体（SNARE）蛋白SYP61作为膜定位泛素连接酶ATL31的新型泛素化靶标。SYP61是拟南芥中膜运输的关键成分。SYP61在体外和植物中被ATL31泛素化为K63连接的链。SYP61的组合式突变体对碳（C）/氮（N）-营养素胁迫的破坏非常敏感，表明其在植物对营养素的动态平衡中的关键作用。我们还发现SYP61的泛素化状态受C / N营养素可用性的影响。这些结果提供了SNARE蛋白的泛素化在植物生理学中具有重要作用的可能性。