Salt stress increases the Ca2+-independent phosphoenolpyruvate carboxylase kinase activity in Sorghum leaves
2001
Echevarria, C. | Garcia-Maurino, S. | Alvarez, R. | Soler, A. | Vidal, J.
In C4 plants, the photosynthetic enzyme phosphoenolpyruvate carboxylase (PEPCase; EC 4.1.1.31) is subjected to a phosphorylation process via the light-dependent up-regulation of a Ca(2+)-independent PEPCase-kinase. The present work aimed to study the effect of salt stress on PEPCase phosphorylation in Sorghum vulgare Pers. leaves. The growth of salt-treated plants was reduced compared with that of the control plants. PEPCase activity modestly increased (around 20-40%) whereas PEPCase phosphorylation was markedly enhanced, on a protein basis, in extracts from illuminated leaves. The enhanced protein kinase activity was found to display a low molecular mass in the range 32-35 kDa, to be independent of Ca(2+) and to be up-regulated by light. Furthermore, up-regulation was blocked in vivo by the cytosolic protein synthesis inhibitor cycloheximide. Collectively, these data demonstrated that salinity stress altered the Ca(2+)-independent PEPCase-kinase, presumably by increasing the mesophyll content of the enzyme. Potassium chloride, but not abscisic acid, mimicked the effect of NaCl on PEPCase-kinase activity.
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