Nitric Oxide and polyamines are involved in the regulation of wheat nitrate reductase

ROSALES E.P, PAGANO, E; IANNONE, M.F., GROPPA, M.D., BENAVIDES M. P.

Tucumán, Argentina

Congreso; XLV Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular. SAIB; 2009

SAIB

Nitric oxide is a molecule which origin in plants is still discussed. Nitrate reductase is proposed to be involved in NO biosynthesis while polyamines (Pas), that share arginine as a common precursor with NO, are nitrogen compounds that can modulate NR. The aim of this work was to study a possible modulation of NR by NO and the effect of PAs on the NR. Wheat leaf segments were incubated with 10, 100 y 500 µM SNP; and with 0.1-1 mM Put, Spm and Spd during 6, 9, 16 and 21 h. At shorter times, 0.1 mM of the three PAs decreased significantly NR activity, while at 21 h, the activity increased. Only Put and Spm produced a similar effect when were used at 1 mM. To evaluate if NO participated in the initial inhibition caused by Put, we tested the recovery of the activity in the presence of c-PTIO and effectively, the effect produced by Put was mediated by NO. Sodium nitroprusside, produced a strong inhibition of the NR activity from the lowest concentration used. We confirmed that NO was involved in the inhibition using c-PTIO to reversed the effect. Although a clear inhibition of the activity was observed, no changes were observed in the  NR protein expression. Then, we investigated the presence of the NO-tyr on the NR, with negative results. To summarize, NO and PAs participate in the regulation of NR, with NO as intermediate in the PAs effect and the mechanism involved still unknown.