Plasma membrane H-ATPase activity is involved in adaptation of tomato calli to NaCl |
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Authors: | Kerkeb Loubna Donaire Juan Pedro Rodríguez-Rosales María Pilar |
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Institution: | Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, CSIC, Apartado 419, E-18080 Granada, Spain |
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Abstract: | A tomato ( Lycopersicon esculentum Mill. cv. Pera) callus culture tolerant to NaCl was obtained by successive subcultures of NaCl-sensitive calli in medium supplemented with 50 m M NaCl. NaCl-tolerant calli grew better than NaCl-sensitive calli in media supplemented with 50 and 100 m M NaCl. Analysis of callus ion content showed a strong increase in Na+ and Cl? both in NaCl-tolerant and -sensitive calli grown in media containing NaCl for one subculture. Cells from NaCl-tolerant calli showed a higher H+ extrusion activity than those from NaCl-sensitive calli grown for one subculture in the presence of NaCl. The inhibition of H+ extrusion by NaCl-sensitive cells was correlated with an inhibition of microsomal vanadate-sensitive H+-ATPase (EC 3.6.1.35) and ATP-dependent H+ transport, while the stimulation of H+ extrusion by cells tolerant to 50 m M NaCl was correlated with an increase in plasma membrane ATP-dependent H+ transport. The increase of ATP-dependent H+ extrusion in plasma membranes isolated from 50 m M NaCl-tolerant calli was not a result of stimulation of a vanadate-sensitive ATP hydrolytic activity or an increase in passive permeability to H+. Relative to NaCl-sensitive calli, plasma membrane H+-ATPase from calli tolerant to 50 m M NaCl showed a lower Km for Mg2+-ATP. Our results indicate that tolerance of tomato calli to 50 m M NaCl increases the affinity of plasma membrane H+-ATPase for the substrate ATP and stimulates the H+-pumping activity of this enzyme without modifying its phosphohydrolytic activity. |
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