CEFOBI   05405
CENTRO DE ESTUDIOS FOTOSINTETICOS Y BIOQUIMICOS
Unidad Ejecutora - UE
artículos
Título:
Alteration of Organic Acid Metabolism in Arabidopsis Overexpressing the Maize C4 NADP-Malic Enzyme Causes Accelerated Senescence during Extended Darkness
Autor/es:
HOLGER FAHNENSTICH *; MARIANA SAIGO * IGUAL CONTRIBUCIÓN; MICHAELA NIESSEN; MARÍA I. ZANOR; CARLOS ANDREO; ALISDAIR FERNI; MARÍA FABIANA DRINCOVICH; ULF-INGO FLÜGGE; VERÓNICA MAURINO
Revista:
PLANT PHYSIOLOGY.
Editorial:
American Society of Plant Biologists
Referencias:
Año: 2007 vol. 145 p. 640 - 652
ISSN:
0032-0889
Resumen:
The full-length cDNA encoding the maize (Zea mays) C4 NADP-malic enzyme was expressed in Arabidopsis (Arabidopsis thaliana) under the control of the cauliflower mosaic virus 35S promoter. Homozygous transgenic plants (MEm) were isolated with activities ranging from 6- to 33-fold of those found in the wild type. The transformants did not show any differences in morphology and development when grown in long days; however, dark-induced senescence progressed more rapidly in MEm plants compared to the wild type. Interestingly, senescence could be retarded in the transgenic lines by exogenously supplying glucose, sucrose, or malate, suggesting that the lack of a readily mobilized carbon source is likely to be the initial factor leadingto the premature induction of senescence in MEm plants. A comprehensive metabolic profiling on whole rosettes allowed determination of approximately 80 metabolites during a diurnal cycle as well as following dark-induced senescence and during metabolic complementation assays. MEm plants showed no differences in the accumulation and degradation of carbohydrates with respect to the wild type in all conditions tested, but accumulated lower levels of intermediates used asrespiratory substrates, prominently malate and fumarate. The data indicated that extremely low levels of malate and fumarate are responsible for the accelerated dark-induced senescence encountered in MEm plants. Thus, in prolonged darkness these metabolites are consumed faster than in the wild type and, as a consequence, MEm plants enter irreversible senescence morerapidly. In addition, the data revealed that both malate and fumarate are important forms of fixed carbon that can be rapidly metabolized under stress conditions in Arabidopsis.