Inhibition of Phosphoenolpyruvate carboxylase (PEPC) by phosphatidic acid (PA) is modulated by nutrient availability in Arabidopsis thaliana plants

• Cirenia Arias ^[1] ; Cristina Echevarría ^[1] ; Sofía García-Mauriño ^[1] ; José Antonio Monreal ^[1]
  1. [1] Universidad de Sevilla

     Universidad de Sevilla

     Sevilla, España

     
• Localización: SEFV 2011: programa de sesiones y resúmenes de conferencias plenarias e invitadas / coord. por Vicent Arbona Mengual, Rosa María Pérez Clemente, María Fernanda López Climent, Aurelio Gómez Cadenas, 2011, ISBN 978-84-8021-805-4, pág. 31
• Idioma: inglés
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• Resumen

  • Phosphoenolpyruvate Carboxylase (PEPC, EC4.1.1.31) is a ubiquitous cytosolic enzymecatalyzing the irreversible β-carboxylation of phosphoenolpyruvate (PEP) to form oxaloacetateand inorganic phosphate. PEPC plays a crucial role in C4 and CAM photosynthesis performingthe initial fixation of atmospheric CO2, but it also has an anaplerotic function in coordinatingcarbon and nitrogen metabolism in all plants. Recently, C3 PEPC from tomato and Arabidopsissuspension-cultured cells was described to bind phosphatidic acid (PA). We have shown that C4PEPC from sorghum leaves binds phosphatidic acid (PA) and its activity is inhibited by thelipid. However, C3 PEPC from sorghum roots or Arabidopsis shoots or roots did not show sucha binding nor inhibition pattern. Interestingly, when C3 PEPC from Arabidopsis suspensionculturedcells was used, the enzyme was found to be inhibited by PA in a manner depending onthe age of the culture, being more bound and inhibited as older was the culture (3 days vs 7 daysafter refreshing the cultures). These results lead us to study whether this different behaviorbetween C3 PEPC from shoots/roots and cells was due to a stress related to nutrient starvation. Ithas been reported that phosphate starvation induces higher expression of PEPC genes andposttranslational modifications of the enzyme in Arabidopsis plants or cells. Therefore, the aimof this work was to analyze possible transcriptional and/or posttranslational modificationsoccurring in Arabidopsis plants growing in hydroponical cultures in response to some nutrientdeficiencies, namely phosphate, nitrogen and iron starvation, that could impact on PEPC-PAinteraction. After 3 weeks of treatment, the inhibition by PA of the PEPC from Arabidopsisshoots was higher in the plants treated without nitrogen, and lower in those treated withoutphosphate or iron. Only the plants without phosphate showed higher PEPC expression andactivity. These results suggest that both transcriptional and posttranslational modifications maybe operating in the modulation of the PEPC-PA binding.