Arabidopsis Root-Type Ferredoxin:NADP(H) Oxidoreductase 2 is Involved in Detoxification of Nitrite in Roots.
Ferredoxin:NADP(H) oxidoreductase (FNR) plays a key role in redox metabolism in plastids. Whereas leaf FNR (LFNR) is required for photosynthesis, root FNR (RFNR) is believed to provide electrons to ferredoxin (Fd)-dependent enzymes, including nitrite reductase (NiR) and Fd-glutamine-oxoglutarate aminotransferase (Fd-GOGAT) in non-photosynthetic conditions. In some herbal species, however, most nitrate reductase activity is located in photosynthetic organs, and ammonium in roots is assimilated mainly by Fd-independent NADH-GOGAT. Therefore, RFNR might have a limited impact on N assimilation in roots grown with nitrate or ammonium nitrogen sources. AtRFNR genes are rapidly induced by application of toxic nitrite. Thus, we tested the hypothesis that RFNR could contribute to nitrite reduction in roots by comparing Arabidopsis thaliana seedlings of the wild type with loss-of-function mutants of RFNR2 When these seedlings were grown under nitrate, nitrite or ammonium, only nitrite nutrition caused impaired growth and nitrite accumulation in roots of rfnr2 Supplementation of nitrite with nitrate or ammonium as N sources did not restore the root growth in rfnr2 Also, a scavenger for nitric oxide (NO) could not effectively rescue the growth impairment. Thus, nitrite toxicity, rather than N depletion or nitrite-dependent NO production, probably causes the rfnr2 root growth defect. Our results strongly suggest that RFNR2 has a major role in reduction of toxic nitrite in roots. A specific set of genes related to nitrite reduction and the supply of reducing power responded to nitrite concomitantly, suggesting that the products of these genes act co-operatively with RFNR2 to reduce nitrite in roots.
RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045 Japan hachiya.takushi@h.mbox.nagoya-u.ac.jp.|Department of Biological Mechanisms and Functions, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601 Japan.
Takushi
T
Hachiya
RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045 Japan.
Nanae
N
Ueda
Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
Munenori
M
Kitagawa
School of Biological and Chemical Sciences, Queen Mary University of London, 7 Mile End Road, London E1 4NS, UK.
Guy
G
Hanke
INRA, Institut Jean-Pierre Bourgin, UMR1318, ERL CNRS 3559, Saclay Plant Sciences, RD10, F-78026 Versailles, France.
Akira
A
Suzuki
Laboratory of Regulation of Biological Reaction, Institute for Protein Research, Osaka University, Suita, Osaka, 565-0871 Japan.
Toshiharu
T
Hase
RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045 Japan.|Department of Biological Mechanisms and Functions, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601 Japan.
Hitoshi
H
Sakakibara
D064751:Ammonium Compounds / Q000494:pharmacology; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D008658:Inactivation, Metabolic / Q000187:drug effects; D016254:Mutagenesis, Insertional / Q000235:genetics; D009154:Mutation / Q000235:genetics; D009573:Nitrites / Q000378:metabolism* / Q000494:pharmacology; D009584:Nitrogen / Q000494:pharmacology; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D020033:Protein Isoforms / Q000378:metabolism
D064751:Ammonium Compounds; D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D009573:Nitrites; D020033:Protein Isoforms; C036483:T-DNA; D010088:Oxidoreductases; C000616112:RFNR2 protein, Arabidopsis; D009584:Nitrogen
Ferredoxin; Ferredoxin:NADP(H) oxidoreductse; Nitrite reduction; Root-type isoform