Intracellular location of NADP+-linked malic enzyme in C3 plants

Ultraviolet light induces anthocyanin biosynthesis in cell cultures of an Afghan cultivar of Daucus carota (Daucus carota L. ssp. sativus). Simultaneous treatment with a fungal elicitor from Pythium aphanidermatum results in an inhibition of the catalytic activity of chalcone synthase (CHS), which in turn correlates with an inhibition of anthocyanin biosynthesis. On immunoblots, one isoenzyme (40 kDa) of CHS disappears upon elicitor treatment. On an mRNA level, only the mRNA for the 40-kDa-CHS is active after treatment with ultraviolet light. After inhibition of anthocyanin biosynthesis by the elicitor the enzyme protein disappears and the CHS mRNA is strongly diminished. This inhibition depends on the concentration of the elicitor. In addition, elicitor treatment leads to an induction of the general phenylpropanoid pathway as well as to the accumulation of 4-hydroxybenzoic acid which is covalently bound to wall polysaccharides of the carrot cells. The possible function of phenylalanine ammonia-lyase in providing precursors for 4-hydroxybenzoic acid is discussed.Abbreviations CHI chalcone isomerase - CHS chalcone synthase - PAL phenylalanine ammonia-lyase - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresisWe are grateful to Professor K. Hahlbrock (Max-Planck-Institut für Züchtungsforschung, Köln, FRG) for providing us with antisera to CHS and PAL, respectively. This work was supported by a grant from the Deutsche Forschungsgemeinschaft and scholarships from the Friedrich-Ebert-Stiftung (J. G.), the Landesgraduierten-förderungsgesetz Baden-Württemberg (J.-P. S) and the Gerhard-Rösch-Stiftung (D. S.). We thank R. Hofmann for her excellent technical assistance.