Department of Biochemistry, Max Planck Institute for Chemical Ecology, 07745 Jena, Germany.
Plant Physiol. 2011 Oct;157(2):876-90. doi: 10.1104/pp.111.181420. Epub 2011 Aug 24.
Stilbenes are dibenzyl polyphenolic compounds produced in several unrelated plant families that appear to protect against various biotic and abiotic stresses. Stilbene biosynthesis has been well described in economically important plants, such as grape (Vitis vinifera), peanut (Arachis hypogaea), and pine (Pinus species). However, very little is known about the biosynthesis and ecological role of stilbenes in spruce (Picea), an important gymnosperm tree genus in temperate and boreal forests. To investigate the biosynthesis of stilbenes in spruce, we identified two similar stilbene synthase (STS) genes in Norway spruce (Picea abies), PaSTS1 and PaSTS2, which had orthologs with high sequence identity in sitka (Picea sitchensis) and white (Picea glauca) spruce. Despite the conservation of STS sequences in these three spruce species, they differed substantially from angiosperm STSs. Several types of in vitro and in vivo assays revealed that the P. abies STSs catalyze the condensation of p-coumaroyl-coenzyme A and three molecules of malonyl-coenzyme A to yield the trihydroxystilbene resveratrol but do not directly form the dominant spruce stilbenes, which are tetrahydroxylated. However, in transgenic Norway spruce overexpressing PaSTS1, significantly higher amounts of the tetrahydroxystilbene glycosides, astringin and isorhapontin, were produced. This result suggests that the first step of stilbene biosynthesis in spruce is the formation of resveratrol, which is further modified by hydroxylation, O-methylation, and O-glucosylation to yield astringin and isorhapontin. Inoculating spruce with fungal mycelium increased STS transcript abundance and tetrahydroxystilbene glycoside production. Extracts from STS-overexpressing lines significantly inhibited fungal growth in vitro compared with extracts from control lines, suggesting that spruce stilbenes have a role in antifungal defense.
芪类化合物是几种不同植物科产生的二苄基多酚化合物，似乎能抵抗各种生物和非生物胁迫。芪类化合物的生物合成在经济上重要的植物中得到了很好的描述，如葡萄（Vitis vinifera）、花生（Arachis hypogaea）和松树（Pinus 种）。然而，关于云杉（Picea）中芪类化合物的生物合成和生态作用知之甚少，云杉是温带和北方森林中一种重要的裸子植物属。为了研究云杉中芪类化合物的生物合成，我们在挪威云杉（Picea abies）中鉴定了两个相似的芪合酶（STS）基因，PaSTS1 和 PaSTS2，它们在锡特卡云杉（Picea sitchensis）和白云杉（Picea glauca）中有高度同源的直系同源物。尽管这三个云杉物种中的 STS 序列具有保守性，但它们与被子植物 STS 有很大的不同。几种类型的体外和体内测定表明，P. abies STS 催化 p-香豆酰辅酶 A 和三个丙二酰辅酶 A 分子的缩合，生成三羟基芪白藜芦醇，但不能直接形成主要的云杉芪类化合物，这些化合物是四羟基化的。然而，在过表达 PaSTS1 的挪威云杉转基因中，显著增加了四羟基芪糖苷白藜芦醇苷和异槲皮苷的产生。这一结果表明，云杉芪类化合物生物合成的第一步是白藜芦醇的形成，然后通过羟基化、O-甲基化和 O-葡萄糖基化进一步修饰，生成白藜芦醇苷和异槲皮苷。用真菌菌丝体接种云杉可增加 STS 转录物的丰度和四羟基芪糖苷的产生。与对照品系相比，STS 过表达系的提取物在体外显著抑制真菌生长，表明云杉芪类化合物在抗真菌防御中具有作用。
