Orosomucoid Proteins Interact with the Small Subunit of Serine Palmitoyltransferase and Contribute to Sphingolipid Homeostasis and Stress Responses in Arabidopsis
Orosomucoid Proteins Interact with the Small Subunit of Serine Palmitoyltransferase and Contribute to Sphingolipid Homeostasis and Stress Responses in Arabidopsis
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DOI：
10.1105/tpc.16.00574
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发表时间：
2016-12-01
期刊：
影响因子：
11.6
通讯作者：
Yao, Nan
中科院分区：
文献类型：
--
作者：
Li, Jian;Yin, Jian;Yao, Nan
丝氨酸棕榈酰转移酶 (SPT) 是一种吡啶酚-59-磷酸依赖性酶，催化鞘脂生物合成的第一步和限速步骤。在人类和酵母中，类粘蛋白 (ORM) 负向调节 SPT，从而在维持鞘脂水平方面发挥重要作用。尽管鞘氨醇中间体作为生物活性分子很重要，但植物中通过 SPT 调节鞘脂生物合成的机制尚不清楚。在这里，我们鉴定并表征了拟南芥 ORM、ORM1 和 ORM2。 ORM1 和 ORM2 (orm1 amiR-ORM2) 功能丧失会刺激鞘脂从头生物合成，导致鞘脂大量积累，尤其是长链碱基和神经酰胺。酵母双杂交、双分子荧光互补和免疫共沉淀测定证实 ORM1 和 ORM2 与 SPT 小亚基 (ssSPT) 发生物理相互作用，表明 ORM 抑制 ssSPT 功能。我们发现 orm1 amiR-ORM2 植物表现出早期衰老表型，伴随着细胞壁和线粒体中 H2O2 的产生、活跃的囊泡运输以及细胞壁并置的形成。引人注目的是，orm1 amiR-ORM2 植物表现出与内质网应激和防御相关的基因表达增加，并且对氧化应激和病原体感染的抵抗力也增强。综上所述，我们的研究结果表明 ORM 与 SPT 相互作用来调节鞘脂稳态，并在植物的环境胁迫耐受性中发挥关键作用。
Serine palmitoyltransferase (SPT), a pyridoxyl-59-phosphate-dependent enzyme, catalyzes the first and rate-limiting step in sphingolipid biosynthesis. In humans and yeast, orosomucoid proteins (ORMs) negatively regulate SPT and thus play an important role in maintaining sphingolipid levels. Despite the importance of sphingoid intermediates as bioactive molecules, the regulation of sphingolipid biosynthesis through SPT is not well understood in plants. Here, we identified and characterized the Arabidopsis thaliana ORMs, ORM1 and ORM2. Loss of function of both ORM1 and ORM2 (orm1 amiR-ORM2) stimulated de novo sphingolipid biosynthesis, leading to strong sphingolipid accumulation, especially of long-chain bases and ceramides. Yeast two-hybrid, bimolecular fluorescence complementation, and coimmunoprecipitation assays confirmed that ORM1 and ORM2 physically interact with the small subunit of SPT (ssSPT), indicating that ORMs inhibit ssSPT function. We found that orm1 amiR-ORM2 plants exhibited an early-senescence phenotype accompanied by H2O2 production at the cell wall and in mitochondria, active vesicular trafficking, and formation of cell wall appositions. Strikingly, the orm1 amiR-ORM2 plants showed increased expression of genes related to endoplasmic reticulum stress and defenses and also had enhanced resistance to oxidative stress and pathogen infection. Taken together, our findings indicate that ORMs interact with SPT to regulate sphingolipid homeostasis and play a pivotal role in environmental stress tolerance in plants.