Salt stress increases the Ca2+-independent phosphoenolpyruvate carboxylase kinase activity in Sorghum leaves.
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 Ca2+-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 Ca2+ 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 Ca2+-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.
Echevarría
C
C
Departamento de Biología Vegetal, Facultad de Biología, Universidad de Sevilla, Seville, Spain. echeva@cica.es
Garcia-Mauriño
S
S
Alvarez
R
R
Soler
A
A
Vidal
J
J
D000040:Abscisic Acid / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D008027:Light; D010766:Phosphorylation; D010788:Photosynthesis / Q000502:physiology; D010937:Plant Growth Regulators / Q000494:pharmacology*; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D006109:Poaceae / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology*; D015854:Up-Regulation
D010937:Plant Growth Regulators; D012965:Sodium Chloride; D000040:Abscisic Acid; C069767:phosphoenolpyruvate carboxylase kinase; D017346:Protein Serine-Threonine Kinases; D002118:Calcium