, Volume 163, Issue 3, pp 370–375 | Cite as

Repair in vitro of nitrate reductase-deficient tobacco mutants (cnxA) by molybdate and by molybdenum cofactor

  • Ralf R. Mendel
  • Andreas J. Müller


Two nitrate reductase-deficient mutant cell lines (CnxA68/2, CnxA101) of Nicotiana tabacum are shown to be repairable under in-vitro conditions by (i) molybdate or (ii) by preparations of active molybdenum cofactor of homologous or heterologous origin, thereby yielding about 20% and 80%, respectively, of the corresponding wild-type NADH-nitrate reductase (EC activity. In-vitro repair of nitrate reductase activity is dependent on sulphydryl-group protecting reagents and ethylenediaminetetraacetic acid (EDTA) in the extraction medium, the nitrogen source in the growth medium and the age of the cells. The results support the conclusion that the cnxA gene controls the insertion of molybdenum into the molybdenum cofactor. They are consistent with the idea of two interlinked pathways for the metabolic processing of molybdenum acquisition, one involving the synthesis of the structural moiety of the molybdenum cofactor and the other involving processing of the molybdate anion.

Key words

Molybdenum Mutant (NicotianaNicotiana (nitrate reductase) Nitrate reductase mutant 



ethylene diaminetetraacetic acid


molybdenum cofactor


nitrate reductase


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Copyright information

© Springer-Verlag 1985

Authors and Affiliations

  • Ralf R. Mendel
    • 1
  • Andreas J. Müller
    • 1
  1. 1.Zentralinstitut für Genetik und KulturpflanzenforschungAkademie der Wissenschaften der DDRGaterslebenGerman Democratic Republic

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