Journal Article

Metabolization of the Artificial Secondary Metabolite 4-Hydroxybenzoate in <i>ubi</i>C-Transformed Tobacco

Shu-Ming Li, Zhao-Xin Wang, Emmanuel Wemakor and Lutz Heide

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 38, issue 7, pages 844-850
Published in print January 1997 | ISSN: 0032-0781
Published online January 1997 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029243
Metabolization of the Artificial Secondary Metabolite 4-Hydroxybenzoate in ubiC-Transformed Tobacco

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Transgenic Nicotiana tabacum cell cultures formed a new, artificial secondary metabolite, i.e. 4-hydroxyben-zoate (4HB), by expression of the bacterial gene ubiC, which encodes chorismate pyruvate-lyase. 4HB was converted in the cells to two different glucosides, i.e. 4-O-(1-rβ-D-gIucosyl)benzoic acid (4HB0G) and 4HB l-rβ-D-glucosyl ester (4HBCOOG). The same metabolization was also observed with exogenously fed 4HB. This glucosylation is catalyzed by constitutively expressed glucosyltransferases which could be detected in cell-free extracts of transgenic and untransformed cells in the same activity. The enzymes forming the two respective glucosides differ in their pH optima, their affinity for 4HB and their regulation. Both in vivo and in cell-free extracts, 4HBOG is the main product at low 4HB concentration, and 4HBCOOG at high 4HB concentration. Whereas 4HB0G is accumulated as an apparently stable secondary metabolite, 4HBCOOG presents a metabolically active form of 4HB. After feeding of [U-14C]4HB, a transient accumulation of 4HBC00G was followed by incorporation of radioactive 4HB into the cell wall, suggesting that 4HBCOOG, but not 4HBOG serves as precursor of cell wall bound 4HB

Keywords: Cell wall; Glucosyltransferase; 4-Hydroxybenzoate; Nicotiana tabacum; Transgenic plants; ubiC gene

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Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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