Overrepresentation of Elements Recognized by TCP-Domain Transcription Factors in the Upstream Regions of Nuclear Genes Encoding Components of the Mitochondrial Oxidative Phosphorylation Machinery

WELCHEN, ELINA AND GONZALEZ DANIEL

PLANT PHYSIOLOGY.

Año: 2006 p. 540 - 545

0032-0889

The promoters of the Arabidopsis thaliana cytochrome c genes, Cytc-1 and Cytc-2, were analyzed using plants transformed with fusions to the b-glucuronidase coding sequence. Histochemical staining of plants indicated that the Cytc-1 promoter directs expression in root and shoot meristems and in anthers. In turn, plants transformed with the Cytc-2 promoter fusions showed expression in vascular tissues of cotyledons, leaves, roots, and hypocotyls, and also in anthers. Quantitative measurements in extracts prepared from different organs suggested that expression of Cytc-1 is higher in flowers, while that of Cytc-2 is higher in leaves. The analysis of a set deletions and site-directed mutants of the Cytc-1 promoter indicated that a segment located between –147 and –156 from the translation start site is required for expression and that site II elements (TGGGCC/T) located in this region, coupled with a downstream internal telomeric repeat (AAACCCTAA), are responsible for the expression pattern of this gene. Proteins present in cauliflower nuclear extracts, as well as a recombinant protein from the TCP-domain family, were able to specifically bind to the region required for expression. We propose that expression of the Cytc-1 gene is linked to cell proliferation through the elements described above. The fact that closely located site II motifs are present in similar locations in several genes encoding subunits of cytochrome c oxidase or proteins involved in its biogenesis suggests that these elements may be the target of factors that co-ordinate the expression of nuclear genes encoding components of this part of the mitochondrial respiratory chain.