Excretion of triacylglycerol as a matrix lipid facilitating apoplastic accumulation of a lipophilic metabolite shikonin
Excretion of triacylglycerol as a matrix lipid facilitating apoplastic accumulation of a lipophilic metabolite shikonin
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DOI：
10.1093/jxb/erac405
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发表时间：
2022-10-12
影响因子：
6.9
通讯作者：
Yazaki，Kazufumi
中科院分区：
文献类型：
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作者：
Tatsumi，Kanade;Ichino，Takuji;Yazaki，Kazufumi
植物产生多种亲脂代谢物，其中许多由细胞分泌并在胞体中积累。这些化合物通常起到保护植物免受环境胁迫的作用。然而，人们对这些亲脂性化合物是如何分泌到外胞体空间的知之甚少。本研究以产紫草素培养细胞为实验模型系统，利用紫草素产率高、培养诱导性强的特点，对其亲脂代谢产物的分泌进行了分析。紫草素衍生物是一种亲脂性的红色萘醌类化合物，只在这些细胞的外胞间隙和完整植物的根表皮中积累。显微分析表明，紫草素以大量颗粒的形式积聚在细胞壁上。脂质组学分析显示。红细胞培养的细胞分泌相当一部分三酰甘油（占总三酰甘油的24-38%），主要由饱和脂肪酸组成。此外，体外重构实验表明，三酰基甘油将紫草素衍生物与磷脂包封形成脂滴状结构。这些发现提示了三酰基甘油作为基质脂质的新作用，这是一种参与特殊亲脂代谢产物分泌的分子成分。
Plants produce a large variety of lipophilic metabolites, many of which are secreted by cells and accumulated in apoplasts. These compounds often play a role to protect plants from environmental stresses. However, little is known about how these lipophilic compounds are secreted into apoplastic spaces. In this study, we used shikonin-producing cultured cells ofLithospermum erythrorhizonas an experimental model system to analyze the secretion of lipophilic metabolites, taking advantage of its high production rate and the clear inducibility in culture. Shikonin derivatives are lipophilic red naphthoquinone compounds that accumulate exclusively in apoplastic spaces of these cells and also in the root epidermis of intact plants. Microscopic analysis showed that shikonin is accumulated in the form of numerous particles on the cell wall. Lipidomic analysis showed thatL. erythrorhizoncultured cells secrete an appreciable portion of triacylglycerol (24–38% of total triacylglycerol), composed predominantly of saturated fatty acids. Moreover,in vitroreconstitution assay showed that triacylglycerol encapsulates shikonin derivatives with phospholipids to form lipid droplet-like structures. These findings suggest a novel role for triacylglycerol as a matrix lipid, a molecular component involved in the secretion of specialized lipophilic metabolites.