CEFOBI   05405
CENTRO DE ESTUDIOS FOTOSINTETICOS Y BIOQUIMICOS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Regulation of mitochondrial oxidation of L-malate through differential subunit association of malic enzyme
Autor/es:
MARCOS A. TRONCONI
Lugar:
La Plata
Reunión:
Conferencia; XXVIII Reunión Argetnina de Fisiología Vegetal; 2010
Institución organizadora:
Asociación Sociedad Argentina de Fisiología Vegetal
Resumen:
The
Arabidopsis thaliana genome contains two genes encoding the
mitochondrial NAD-malic enzyme
(NAD-ME), nad-me1 and nad-me2. The encoded proteins, NAD-ME1 and -2, assemble as active
homodimers; however, they can also associate to form a heterodimeric enzyme (NAD-MEH) in vivo and in vitro. Although nad-me1 and -2 genes show a
similar pattern of expression in mature organs of Arabidopsis, NAD-ME1 and -2
accumulate at different levels in the separate components of floral organ. Such
changes in the protein ratio can influence the formation of the three
different NAD-ME native associations. Recombinant NAD-ME1, -2 and -H isoforms
differ in its interaction with the substrates, L-malate and NAD, and are
differentially regulated by intermediates of glycolysis or Krebs cycle, which
suggest a specificity of function of each entity in the C4-organic
acid metabolism. Another evidence that support this hypothesis arise from the
specific expression shown by nad-me
genes in plants under different nutritional and ambient conditions. In
addition, the analysis of mutant plants lacking of one or both nad-me functional genes revealed in each
case a metabolic perturbation that was gene mutated-dependent. On another hand,
the metabolic status of the double mutant plant, which not presents detectable
NAD-ME activity, was different depending on the light/dark period. In this
regard, during the day double mutant exhibit little changes with a higher level
of some sugars, while in nocturne period the perturbation is more accentuated
with contend of several amino acid enhanced compared to wild type plant. Also,
NAD-ME activity in leaves is higher in the dark, because a mayor expression of nad-me genes. These results reveal a
major role of mitochondrial NAD-ME in the coordination of the carbon and nitrogen
metabolisms during night periods in Arabidopsis.