Involvement of Oxidative Burst in Isoflavonoid Metabolism in Elicited Cell Suspension Cultures of Pueraria lobata

Hyung-Hwan Park. Takashi Hakamatsuka, Ushio Sankawa, and Yutaka Ebizuka Faculty of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan Z. Naturforsch. 50c, 824-832 (1995); received July 25/September 26. 1995 Pueraria lobata, Isoflavonoids, Malonylglucosides, Elicitation, Oxidative Burst Hydrogenperoxide exogenously administerd to the suspension-cultured cells of Pueraria lobata stimulated a rapid disappearance of the constitutive isoflavonoids (malonylglucosides of daidzein and genistein) from the methanol soluble fraction of the cells, in a similar manner as observed in the cells treated with yeast extract or glycoprotein preparation of P hyto­ phthora megasperma f. sp. glycinea. Rapid generation of H20 2 was detected within 10 min after elicitation at the cell surface, presumably preceded by the activation of plasma mem­ brane NAD(P)H-oxidases. Pretreatm ent of some representative NAD(P)H-oxidase inhibi­ tors such as SHAM, DEDTC and KCN (1 mM each) to the cells 1 h before elicitation resulted in almost complete inhibition of the elicitor-stimulated metabolism of isoflavonoids for 4 h, whereas treatment of the inhibitors at 1 h after elicitation showed no significant effect on the rapid isoflavonoid metabolism. These findings suggest that this type of response to elicita­ tion could be regarded as a plausible initial defense strategy prior to the appearance of de novo synthesized defensive barriers such as phytoalexins and lignin in plant-pathogen in­ teraction.