Evidence for the involvement of plasma-membrane-bound nitrate reductase in signal transduction during blue-light stimulation of nitrate uptake in Chlorella saccharophila |
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Authors: | Christine Stöhr Ulrich Glogau Michael Mätschke Rudolf Tischner |
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Affiliation: | (1) Institut für Botanik, Technische Hochschule, Schnittspahnstrasse 3, D-64287 Darmstadt, Germany;(2) Pflanzenphysiologisches Institut der Universität Göttingen, Untere Karspüle 2, D-37073 Göttingen, Germany |
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Abstract: | Nitrate uptake in Chlorella saccharophila (Krüger) Nadson was found to be stimulated by blue light, leading to a doubling of the rate. In the presence of background red light (300 mol photons · m-2 · s-1), only 15–20 mol photons · m-2 · s-1 of blue light was sufficient to saturate this increased uptake rate. Incubation of Chlorella cells with anti-nitrate-reductase immunoglobulin-G fragments inhibited blue-light stimulation. However, ferricyanide (10 M) doubled and dithiothreitol (100 M) inhibited the stimulatory effect of blue light. Among the protein-kinase inhibitors used, only staurosporine (10 M) prevented the blue-light stimulation. Phosphatase inhibitors were without effect and sodium vanadate totally inhibited nitrate uptake, pointing to an involvement of the plasma-membrane ATPase. Preincubation of the cells with calmodulin antagonists or calcium ionophores did not significantly reduce blue-light stimulation of nitrate uptake. The data are discussed with regard to transduction of the signal for blue-light stimulation of nitrate uptake and the possibility that the plasma-membrane-bound nitrate reductase is the blue-light receptor.Abbreviations Chl chlorophyll - DMSO dimethylsulfoxide - 1,2-DHG 1,2-dihexanoylglycerol - ML-9 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine - NR nitrate reductase - H-7 1-(5-isoquinolinyl-sulfonyl)-2-methylpiperazine - IgG immunoglobulin G - PFD photon flux density - PM plasma membrane - W-7 N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamideThis work was supported by a grant from the Deutsche Forschungs-gemeinschaft to R.T. |
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Keywords: | Blue-light Chlorella Nitrate reductase (plasma-membrane-bound) Nitrate uptake |
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