Salt modulation of vacuolar H+-ATPase and H+-pyrophosphatase activities in Vigna unguiculata
2001
Otoch, M. de L.O. | Sobreira, A.C.M. | Aragao, M.E.F. de | Orellano, E.G. | Lima, M. da G.S. | Fernandes de Melo, D.
Salt modulation of the tonoplast H(+)-pumping V-ATPase and H(+)-PPase was evaluated in hypocotyls of Vigna unguiculata seedlings after 3 and 7 days of treatment. In 3-day-old seedlings, treatment with 100 mmol/L NaCl decreased the proton transport and hydrolytic activities of both the V-ATPase and the H(+)-PPase. After 7 days, the proton transport and hydrolysis activities of the V-ATPase were higher, while the H(+)-PPase activities were lower in seedlings. Western blot analysis of A- and B-subunits of V-ATPase revealed that the protein content of the two subunits varied in parallel with their activities, i.e. to a higher activity corresponded a higher protein content of the subunits and vice versa. Contrarily, Western blot analysis of H(+)-PPase levels failed to show any correlation with PPase activity, suggesting a partial enzyme inactivation. The results indicate that salt stress induces V-ATPase expression in V. unguiculata with concomitant enhancement of its activity as a homeostatic mechanism to cope with salt stress. Under the same conditions PPase is inhibited.
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