Nitrate reductase activity in Paul's scarlet rose suspension cultures and the differential role of nitrate and molybdenum in induction |
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| Authors: | R. W. Jones A. J. Abbott E. J. Hewitt G. R. Best E. F. Watson |
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| Affiliation: | (1) Long Ashton Research Station, University of Bristol, BS18 9AF Bristol, UK;(2) Present address: Dept. of Land Resource Science, University of Guelph, N1G 2W1, Ontario, Canada |
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| Abstract: | Induction of nitrate reductase (EC 1.6.6.1) activity was measured in Paul's Scarlet rose cell suspensions cultured in media containing nitrate (NO3-) or urea (U) as nitrogen source, and with (+Mo) or without molybdenum (-Mo). There was a lag of 30 min during induction by NO3-in +Mo cultures but no lag occurred during induction after adding Mo to NO3--Mo or to U-Mo cultures preincubated with NO3-. Actinomycin D, cycloheximide, and puromycin completely blocked induction by NO3-, but had no effect on the initial rate of induction by Mo. Cycloheximide and puromycin blocked induction by NO3-more quickly than actinomycin D. Induction by NO3-appeared to involve mRNA-dependent synthesis of apoprotein followed by rapid activation with molybdenum in intact cells independently of protein synthesis. Nitrate-induced apoprotein appeared less stable than the holoenzyme. When induced by NO3-in the absence of Mo, apoprotein concentration was about half the amount of maximally induced nitrate reductase. Cycloheximide stabilised preformed nitrate reductase which disappeared steadily in the presence of puromycin. Apoprotein was not stabilised by either antimetabolite.Abbreviations Mo molybdenum - NO3-+Mo standard, MX1 culture medium - NO3--Mo MX1 medium purified of Mo - NR nitrate reductase - PSR Paul's Scarlet rose - U urea - U+Mo MX1 medium with NO3-replaced by urea - U-Mo MX1 medium with NO3-replaced by urea and also purified of Mo |
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| Keywords: | Antimetabolites Cell culture Enzyme induction Molybdenum Nitrate reductase Rosa, Paul's Scarlet |
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