title: Regulation of nitrate reductase by nitric oxide in Chinese cabbage pakchoi (Brassica chinensis L.).
abstract: Nitrate reductase (NR), a committed enzyme in nitrate assimilation, involves generation of nitric oxide (NO) in plants. Here we show that the NR activity was significantly enhanced by the addition of NO donors sodium nitroprusside (SNP) and NONOate (diethylamine NONOate sodium) to the culturing solution, whereas it was decreased by NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (cPTIO). Interestingly, both NO gas and SNP directly enhanced but cPTIO inhibited the NR activities of crude enzyme extracts and purified NR enzyme. The cPTIO terminated the interaction between NR-generated NO and the NR itself. Furthermore, the NR protein content was not affected by the SNP treatment. The investigation of the partial reactions catalysed by purified NR using various electron donors and acceptors indicated that the haem and molybdenum centres in NR were the two sites activated by NO. The results suggest that the activation of NR activity by NO is regulated at the post-translational level, probably via a direct interaction mechanism. Accordingly, the concentration of nitrate both in leaves and roots was decreased after 2 weeks of cultivation with SNP. The present study identifies a new mechanism of NR regulation and nitrate assimilation, which provides important new insights into the complex regulation of N-metabolism in plants.
authors.affiliation: Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health, College of Natural Resources and Environmental Science, Zhejiang University, Hangzhou, 310029, China.
authors.forename: Shaoting
authors.initials: S
authors.lastname: Du
authors.forename: Yongsong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xianyong
authors.initials: X
authors.lastname: Lin
authors.forename: Yue
authors.initials: Y
authors.lastname: Wang
authors.forename: Caixian
authors.initials: C
authors.lastname: Tang
mesh_terms: D001937:Brassica / Q000187:drug effects* / Q000201:enzymology*; D002384:Catalysis / Q000187:drug effects; D003497:Cyclic N-Oxides / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007700:Kinetics; D009280:Naphthaleneacetic Acids / Q000378:metabolism; D050901:Nitrate Reductase / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000494:pharmacology*; D009599:Nitroprusside / Q000494:pharmacology; D010936:Plant Extracts / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology; D013997:Time Factors
chemical_list: D003497:Cyclic N-Oxides; D007093:Imidazoles; D009280:Naphthaleneacetic Acids; D009566:Nitrates; D010936:Plant Extracts; D009599:Nitroprusside; C079391:2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; D009569:Nitric Oxide; C034182:1-naphthaleneacetic acid; D050901:Nitrate Reductase