Metabolic Regulation of Genes Encoding Cytochrome c and Cytochrome c Oxidase Subunit Vb in Arabidopsis.

WELCHEN, ELINA.; CHAN, RAQUEL L.; GONZALEZ, DANIEL H.

Villa Carlos Paz, Córdoba

Congreso; XXXVII Reunión anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB).; 2001

METABOLIC REGULATION OF GENES ENCODING CYTOCHROME C AND CYTOCHROME C OXIDASE SUBUNIT Vb IN ARABIDOPSIS. We have analyzed the expression of four Arabidopsis nuclear genes encoding components of the mitochondrial cyanide-sensitive respiratory pathway: two cytochrome c oxidase subunit Vb (COX5b) and two cytochrome c (Cytc) genes. Northern blot analysis indicated that the four genes are mainly expressed in leaves and flowers, with only minor relative differences between different organs. Incubation of dark-adapted plants in solutions containing metabolizable sugars produced an increase in transcript levels. The effect of carbohydrates was more pronounced for Cytc than for COX5b genes, but showed the same time- and concentration-dependence for the four genes, suggesting the operation of a common regulatory mechanism. Light also produced an increase in transcript levels, though smaller than that produced by sugars. In the presence of ammonium, higher transcript levels were observed with respect to plants treated with either nitrogen-free or nitrate solutions. Nitrate, on the other hand, produced a slight decrease in transcript levels and abolished the inducing effect of ammonium when both compounds were combined. Our results suggest that carbon and nitrogen metabolites act in concert to regulate the expression of different components of the cyanide-sensitive respiratory pathway. This is the first evidence of a coordinated metabolic regulation of components of the mitochondrial respiratory chain.