01933naa a2200277 a 450000100080000000500110000800800410001910000270006024501050008726000090019252011330020165000210133465000240135565000140137965000290139365000140142265000200143665000100145665300220146670000200148870000180150870000240152670000280155070000220157877300550160020030222014-12-17       2014    bl uuuu     u00u1 u    #d1 aALVAREZ-PIZARRO, J. C.  aPlasma membrane H+-ATPase in sorghum roots as affected by potassium deficiency and nitrogen sources.  c2014  aAbstract: We studied the influence of inorganic nitrogen sources (NO3- or NH4+) and potassium deficiency on expression and activity of plasma membrane (PM) H+-ATPase in sorghum roots. After 15 d of cultivation at 0.2 mM K+, the plants were transferred to solutions lacking K+ for 2 d. Then, K+ depletion assays were performed in the presence or absence of vanadate. Further, PMs from K+-starved roots were extracted and used for the kinetic characterization of ATP hydrolytic activity and the immunodetection of PM H+-ATPase. Two major genes coding PM H+-ATPase (SBA1 and SBA2) were analyzed by real-time PCR. PM H+-ATPase exhibited a higher Vmax and Km in NH4+-fed roots compared with NO3--fed roots. The optimum pH of the enzyme was slightly lower in NO3- -fed roots than in NH4+ -fed roots. The vanadate sensitivity was similar. The expressions of SBA1 and SBA2 were increased in roots grown under NH4+. Concomitantly, an increased content of the enzyme in PM was observed. The initial rate of K+ uptake did not differ between plants grown with NO3- or NH4+, but it was significantly reduced by vanadate in NH4+-grown plants.  aAmmonium nitrate  aNitrate fertilizers  aPotassium  aFertilizante nitrogenado  aPotássio  aSorghum Bicolor  aSorgo  aNitrato de Amonia1 aGOMES FILHO, E.1 aPRISCO, J. T.1 aGROSSI DE SA, M. F.1 aOLIVEIRA NETO, O. B. de1 aFRAGOSO, R. da R.  tBiologia Plantarumgv. 58, n. 3, p. 507-514, 2014.