Induction of plant phenolic amides by oligosaccharides

用β-1，3-寡糖激发子处理马铃薯块茎圆盘，诱导产生一种酚酰胺类化合物--对香豆胺(PCO)。在本研究收集的每一个马铃薯品种中都观察到了这种诱导。用氚标记的化合物进行的掺入实验表明，PCO的八胺部分是由酪氨酸衍生的。诱导子处理后，块茎组织中游离酪胺的水平增加，而章鱼胺的水平没有显著增加。因此，有人认为酪氨酸被脱羧为酪胺，p-香豆酰基部分从相应的辅酶A硫酯转移到酪胺上，随后的氧化在激发子处理的马铃薯组织中产生PCO。PCO的诱导被认为是由于寡糖激发子引起从头合成的激活而发生的。激发子处理协同提高了负责PCO八胺部分形成的酪氨酸脱羧酶和酪氨羟肉桂酰辅酶A转移酶的活性，以及与苯丙氨酸解氨酶和4-羟基肉桂酸：辅酶A连接酶有关的酶的活性。当激发子在TIron或活性氧清除剂没食子酸正丙酯存在的情况下使用时，PCO的诱导被抑制。碘化二苯醚也能抑制这种诱导作用。膜结合NADPH氧化酶的抑制剂，表明NADPH氧化酶产生的活性氧物种参与了从激发子刺激到激活马铃薯块茎组织中PCO生物合成的信号转导。

A phenolic amide compound, p-coumaroyloctopamine (PCO), is induced in potato tuber disks by the treatment with beta-1,3-oligoglucosaccharide elicitor. The induction was observed in every potato cultivar collected in this study. Octopamine moiety of PCO was shown to be derived from tyrosine by the incorporation experiments using deuterium-labelled compounds. The level of free tyramine in the tuber tissue increased after the elicitor treatment, while no significant increase was observed regarding the octopamine level. Thus it was proposed that tyrosine is decarboxylated to tyramine, to which p-coumaroyl moiety is transferred from the corresponding CoA thioester, and the subsequent oxidation gives PCO in elicitor-treated potato tissue. The induction of PCO was thought to occur as a result of the activation of de novo synthesis caused by the oligosaccharide elicitor. The elicitor treatment coordinately raised the activities of tyrosine decarboxylase and tyramine hydroxycinnamoyl CoA transferase, the enzymes responsible for the formation of the octopamine moiety of PCO, together with those involved with phenylpropanoid metabolism including phenylalanine ammonia lyase and 4-hydroxycinnamic acid : CoA ligase. When the elicitor was applied in the presence of tiron or n-propyl gallate, the scavenger of active oxygen species, the induction of PCO was inhibited. The induction was also inhibited by diphenylene iodide, . an inhibitor of membrane-bound NADPH oxidase, suggesting that the active oxygen species produced by NADPH oxidase are involved with the signal transduction from the elicitor stimulation to the activation of PCO biosynthesis in potato tuber tissues.