Induction of plant phenolic amides by oligosaccharides

用-1,3-低聚糖激发剂处理马铃薯块茎，诱导出一种酚醛酰胺化合物对coumaroyloctopamine （PCO）。本研究收集的每个马铃薯品种均进行了诱导试验。用氘标记化合物的掺入实验表明，PCO的章鱼胺部分来源于酪氨酸。诱导剂处理后，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，提出酪氨酸脱羧为酪胺，对香豆基部分从相应的辅酶a硫酯转移到酪胺，随后氧化产生PCO。PCO的诱导被认为是由于低聚糖激发子引起的从头合成激活的结果。激发剂处理协调提高了酪氨酸脱羧酶和酪胺羟肉桂酰基辅酶a转移酶的活性，这两种酶负责PCO中章鱼胺部分的形成，以及苯丙氨酸解氨酶和4-羟基肉桂酸辅酶a连接酶等苯丙氨酸代谢酶的活性。当激发剂与铁或活性氧清除剂没食子酸正丙酯存在时，对PCO的诱导受到抑制。二苯碘也能抑制这种诱导作用。这表明NADPH氧化酶产生的活性氧参与了从激发子刺激到激活马铃薯茎组织中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.