Sucrose supply enhances phosphoenolpyruvate carboxylase phosphorylation level in in vitro Solanum tuberosum

Abstract

In order to study the effect of exogenous sucrose on the phosphorylation of phosphoenolpyuruvate carboxylase (PEPC), potato plantlets (Solanum tuberosum L. cv. Kennebec) were grown on three modifications of the Murashige and Skoog (MS) medium: 3% sucrose + normal N level (1% Suc + N); 3% sucrose + normal N level (3% Suc + N); 3% sucrose + reduced N level (3% Suc – N). After 20 days of culture, PEPC phosphorylation levels were determined in leaves and roots by means of protein labelling with 32P, and by L-malate inhibition of enzyme activity. Plants grown with 3% Suc + N had the highest phosphorylation level compared to those cultured with 3% Suc and the control (1% Suc + N). These investigations demonstrated clearly that sucrose enhanced phosphorylation. Sucrose or its metabolism may cause PEPC to become less sensitive to L-malate inhibition.