Influence of UVB irradiation on nitrate and ammonium assimilating enzymes in Spirodela polyrhiza

Autor: Manuela Schwalbe, Steffen Teller, Klaus-J. Appenroth, Ralf Oelmüller
Rok vydání: 1999
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Zdroj: Aquatic Botany. 64:19-34
ISSN: 0304-3770
DOI: 10.1016/s0304-3770(99)00005-4
Popis: The influence of UVB radiation on nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), NADH-dependent glutamate synthase (NADH-GOGAT) and ferredoxin-dependent glutamate synthase (Fd-GOGAT) was investigated in fronds and turions of Spirodela polyrhiza. When white light (4.3 W m−2) was supplemented with UVB (0.55 W m−2; λmax = 311 nm), a 40% transient decrease in the growth rate was observed after 12 h UVB irradiation. In addition, the activities of all enzymes investigated, except for the cytoplasmic isoform of GS, were substantially inhibited (NR, 80%; NiR, 32%; GS, 30%; NADH-GOGAT, 36%; Fd-GOGAT, 54% in green fronds). The extent of the inhibition in fronds as well as in turions is in accordance with the assumption that the light-induced increases of enzyme activities are prevented by simultaneous application of UVB. The uptake of nitrate was not influenced by white light or UVB. As shown by western analysis, a correlation between the enzyme activities and their protein amounts was found. Northern analysis revealed that UVB influenced the transcript accumulation of NR but not of Fd-GOGAT. No obvious correlation was observed between the mRNA and the protein amount. This suggests that UVB damage occurs at the transcriptional and post-transcriptional levels as well as at the protein level.
Databáze: OpenAIRE
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