Nitric oxide inhibits nitrate reductase activity in wheat leaves

ROSALES EP; IANNONE, M.F.; GROPPA, M.D.; BENAVIDES M. P.

PLANT PHYSIOLOGY AND BIOCHEMISTRY

ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER

Año: 2011 vol. 49 p. 124 - 130

0981-9428

Nitrate reductase (NR), a committed enzyme in nitrate assimilation, is involved in the generation of nitric oxide (NO) in plants. In wheat leaf segments exposed to sodium nitroprusside (SNP) or S-nitrosoglutathione (GSNO), NR activity was signi*cantly reduced to different degrees between 3 and 21 h, whereas its activity was partially recovered when the NOscavenger cPTIO was used. At 21 h, NR activity decreased from38% with 10 mM SNP to 91% with 500 mM SNP, respect to the C values. S-nitrosoglutathione reduced NR activity between 18% and 26% only at 3 h. When added directly to the incubation solution, NR activity was quickly and strongly inhibited more than 90% by 10 or 50 mMSNP, whereas 10 mMGSNO reduced the enzyme activity an average of 50%, at 30 min of incubation. L-NAME and D-arginine (nitric oxide synthase (NOS) inhibitors) increased NRactivity by 14% and 52% respectively, at 21 h of exposure, leading us to suppose that endogenous NOS-dependent NO formation could also be modulating NR activity. NR protein expression was not affected by 10 or 100 mM SNP at 3 or 21 h of incubation, whereas nitration of tyrosines was not detected in the NR protein. Nitrates, which content increased along the time in the tissues, could be exerting a role in this regulation.mM SNP to 91% with 500 mM SNP, respect to the C values. S-nitrosoglutathione reduced NR activity between 18% and 26% only at 3 h. When added directly to the incubation solution, NR activity was quickly and strongly inhibited more than 90% by 10 or 50 mMSNP, whereas 10 mMGSNO reduced the enzyme activity an average of 50%, at 30 min of incubation. L-NAME and D-arginine (nitric oxide synthase (NOS) inhibitors) increased NRactivity by 14% and 52% respectively, at 21 h of exposure, leading us to suppose that endogenous NOS-dependent NO formation could also be modulating NR activity. NR protein expression was not affected by 10 or 100 mM SNP at 3 or 21 h of incubation, whereas nitration of tyrosines was not detected in the NR protein. Nitrates, which content increased along the time in the tissues, could be exerting a role in this regulation.