利用纤维素酶降解人参(Panax ginseng C.A.Meyer)悬浮细胞的细胞壁制备了内源激发子(CDW).CDW体外诱导了游离人参细胞质膜NADPH氧化酶的活性,激发了活体人参悬浮细胞产生H2O2.CDW还可以诱导提高苯丙氨酸解氨酶(PAL)活性,促进人参鲨烯环氧酶基因(sqe)的转录与人参皂甙的积累.NADPH氧化酶的抑制剂不仅可以抑制CDW体外诱导的质膜NADPH活性而且还可以抑制CDW诱导人参细胞产生H2O2.进而,这些抑制剂还可以抑制CDW诱导PAL活性的提高,以及sqe的转录与人参皂甙的合成.过氧化氢酶与H2O2的粹灭剂也可以抑制CDW激发产生的这些诱导效应.上述结果表明CDW激发质膜NADPH氧化酶的活化与H2O2的产生在介导CDW诱导人参细胞抗性反应中,包括PAL活性的提高与人参皂甙的积累,起了重要的信号转导作用.%Endogenous elicitor, termed cellulase-degraded cell wall (CDW), was prepared from the cellwall of suspension-cultured ginseng (Panax ginseng C.A. Meyer) cells via cellulase degradation. CDW acti-vated the NADPH oxidase activity of isolated plasma membranes and stimulated in vivo H2O2 generation inginseng cell suspensions. CDW also increased the activity of phenylalanine ammonia lyase (PAL), expres-sion of a P. ginseng squalene epoxidase (sqe) gene and saponin synthesis. NADPH oxidase inhibitors inhib-ited bothin vitro NADPH oxidase activity and in vivo H2O2 generation. Induction of PAL activity, saponinsynthesis and sqe gene expression were all inhibited by such inhibitor treatments and reduced by incuba-tion with catalase and H2O2 scavengers. These data indicate that activation of NADPH oxidase and genera-tion of H2O2 are essential signalling events mediating defence responses induced by the endogenouselicitor(s) present in CDW.
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