ROLE OF SITE II MOTIFS IN MITOCHONDRIAL CYTOCHROME C OXIDASE GENE PROMOTERS

MUFARREGE, EDUARDO; CURI, GRACIELA AND GONZALEZ, DANIEL.

Rosario, Argentina

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB); 2006

Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB)

Cytochrome c oxidase (COX) is composed of several subunits, 3 of them encoded by the mitochondrial genome and the rest encoded by the nuclear genome. In this work, we study the structure of the single COX6a and the three COX6b gene promoters from Arabidopsis thaliana. All of these promoters contain copies of a motif named site II (TGGGCC/T) involved in expression in meristematic cells in other genes. We obtained transgenic plants that express the gus (b-glucuronidase) gene under the control of COX6a and COX6b promoter sequences and analyzed GUS enzymatic activity by histochemical assays. Transgenic plants that included COX6a promoter sequences revealed GUS activity only in pollen grains. The COX6b1/3 lines showed similar expression patterns in roots, cotyledon veins, leaf veins, shoot apical meristem and pollen. Deletions of the respective promoters down to approximately -200 (a fragment that included the site II motifs) produced plants with the same expression patterns as those observed with larger fragments. In transgenic plants that contained COX6a and COX6b promoters with mutations in the site II motifs the expression disappeared or was extremely low. The results suggest that site II motifs are essential for expression of all Arabidopsis COX6a and COX6b genes. These motifs may participate in the coordinate regulation of the expression of these genes.