Unveiling the phytoalexin biosynthetic puzzle in salt cress: unprecedented incorporation of glucobrassicin into wasalexins A and B
作者:M. Soledade C. Pedras、Estifanos E. Yaya、Sajjad Hossain
DOI:10.1039/c0ob00265h
日期:——
Salt cress (Thellungiella salsuginea also known as T. halophila) is a wild cruciferous extremophile highly resistant to salt, drought, and cold. The recent discovery that salt cress produces the phytoalexins wasalexins A and B, and the phytoanticipins 1-methoxyglucobrassicin and 4-methoxyglucobrassicin in relatively higher amounts than other cruciferous species, prompted investigation of their biosynthetic relationships. Toward this end, perdeuterated 1-methoxybrassinin, L-Trp, glucobrassicin, 1-methoxyindolyl-3-acetaldoxime, brassinin, and methionine, as well as the corresponding natural abundance compounds, were administered to salt cress plants previously irradiated with UV-light (λmax 254 nm). Remarkably, administration of hexadeuterated glucobrassicin led to incorporation of several deuterium atoms into wasalexins A and B, 1-methoxyglucobrassicin and 4-methoxyglucobrassicin. This unprecedented discovery suggests that glucobrassicin is a biosynthetic precursor of wasalexins and methoxylated glucosinolates in salt cress.
盐芹菜(Thellungiella salsuginea,又名 T. halophila)是一种野生十字花科植物,具有很强的抗盐、抗旱和抗寒能力。最近发现,盐芹产生的植物茎叶素 wasalexins A 和 B,以及植物茎叶素 1-甲氧基葡萄糖苷和 4-甲氧基葡萄糖苷的含量相对高于其他十字花科植物,这促使人们对它们的生物合成关系进行研究。为此,我们给盐菜植物施用了过氘化的 1-甲氧基黄铜甙、L-Trp、葡萄糖黄铜甙、1-甲氧基吲哚基-3-乙酰醛肟、黄铜甙和蛋氨酸,以及相应的天然丰度化合物,然后用紫外线(λmax 254 nm)照射。值得注意的是,施用六氘代化的葡萄糖桔梗苷会导致几个氘原子掺入山葵素 A 和 B、1-甲氧基葡萄糖桔梗苷和 4-甲氧基葡萄糖桔梗苷中。这一史无前例的发现表明,在盐菜中,葡萄糖桔梗苷是wasalexins和甲氧基化葡萄糖苷酸盐的生物合成前体。