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Enhanced H+/ATP coupling ratio of H+-ATPase and increased 14-3-3 protein content in plasma membrane of tomato cells upon osmotic shock
Authors:Kerkeb Loubna  Venema Kees  Donaire Juan Pedro  Rodríguez-Rosales María Pilar
Affiliation:Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, CSIC, Granada, Spain
Abstract:Modulation of proton extrusion and ATP-dependent H+ transport through the plasma membrane in relation to the presence of 14-3-3 proteins in this membrane in response to osmotic shock was studied in tomato ( Lycopersicon esculentum Mill. cv. Pera) cell cultures. In vivo H+ extrusion by cells was activated rapidly and significantly after adding 100 m M NaCl, 100 m M KCl, 50 m M Na2SO4, 1.6% sorbitol or 2 µ M fusicoccin to the medium. The increase in H+ extrusion by cells treated with 100 m M NaCl was correlated with an increase of H+ transport by the plasma membrane H+-ATPase (EC 3.6.1.35), but not with changes in ATP hydrolytic activity of this enzyme, suggesting an increased coupling ratio of the enzyme. Immunoblot experiments showed increased amounts of 14-3-3 proteins in plasma membrane fractions isolated from tomato cells treated with 100 m M NaCl as compared to control cells without changing the amount of plasma membrane H+-ATPase. Together, these data indicate that in tomato cells an osmotic shock could enhance coupling between ATP hydrolysis and proton transport at the plasma membrane through the formation of a membrane 14-3-3/H+-ATPase complex.
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