FUNCTIONAL STUDIES OF PLANT MITOCHONDRIAL CYTOCHROME C OXIDASE GENE PROMOTERS

MUFARREGE E, CURI G, CHAN R, GONZÁLEZ D.

Iguazú-Misiones, Argentina

Congreso; XL Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB); 2004

Sociedad Argentina de investigación en Bioquímica y Biología Molecular

Cytochrome c oxidase (COX) is the terminal respiratory chain complex of mitochondria, and it is involved in oxygen reduction and proton translocation. This complex is composed of 3 subunits encoded in the mitochondrial genome in most organisms, and several subunits encoded in the nuclear genome. In plants, there are 4 polypeptides encoded in the nuclear genome associated with the enzymatic core: COX5b, COX5c, COX6a and COX6b. We have previously obtained evidence of a coordinated control of gene expression for COX5b, COX6a and COX6b in Arabidopsis thaliana. In Arabidopsis there are four genes encoding COX5c subunit and three genes encoding COX6b subunit. In this work, we tried to gain insight into the structure and function of COX5c-3, COX5c-4, COX6b1 and COX6b2 promoter sequences. To perform this analysis, we obtained transgenic plants that express the gus (b-glucuronidase) gene under the control of COX5c-3/4 or COX6b1/2 promoter sequences, and analyzed GUS enzymatic activity by histochemical assays. Transgenic plants, that included both COX5c promoter sequences, revealed GUS activity in the root meristems, cortex and vascular bundle and hairs, in cotyledons blades and veins, in the hypocotyl vascular bundle, in the shoot apical meristem and in leaf veins and trichomes. In mature plants, we observed expression in leaf veins, blades and trichomes, in flowers petals, sepals, stamens, pollen grains, ovary, style and stigma, in siliques veins and stigma (when present) and in developing seeds. In transgenic plants lines that contained COX6b1 promoter sequence, GUS activity is detected in leaf veins and hydathodes, and in flowers sepals veins and blades, ovary, pollen grains and anther filaments. In COX6b2 lines, the GUS expression was significative lower than in COX6b1 lines, and the stained tissues included leaf veins and hydathodes and pollen grains. In some cases, enzymatic activity was also observed in flowers sepals veins and anthers filaments.