AtSCO1, A COPPER CHAPERONE HOMOLOG OF YEAST Sco1p, IS ESSENTIAL DURING EMBRIOGENESIS IN ARABIDOPSIS PLANTS

CAROLINA V. ATTALLAH, ELINA WELCHEN, DANIEL H. GONZÁLEZ

Rosario, Santa Fe. Argentina.

Congreso; XXVII Reunión Nacional de la Asociación Argentina de Fisiología Vegetal (SAFV); 2008

Sociedad Argentina de Fisiología Vegetal

The assembly of cytochrome c oxidase (COX) involves a number of auxiliary proteins. Some of these proteins are implicated in metallation of the two copper centers present in COX. Yeast Sco1p is a constituent of the mitochondrial inner membrane involved in the formation of the CuA center and deltasco1 cells are respiratory-deficient. In addition, deltasco1 cells are sensitive to hydrogen peroxide which suggests that Sco1p has a mitochondrial function independent of copper metallation. We have identified Arabidopsis plants with T-DNA insertions in two genes that encode proteins with homology to yeast Sco1p. Homozygote mutant plants with insertions in one of these genes, located in chromosome 4, have no obvious phenotype. In turn, segregation analysis of heterozygote mutant plants in the other gene, AtSCO1, located in chromosome 3, suggests that its function is required at early stages of plant development. Siliques of these plants contain 25% abnormal seeds with embryos arrested at the heart or torpedo stage. To establish a causal link between genotype and phenotype we used complementation with the AtSCO1 cDNA. This approach allowed us to obtain plants homozygous for the T-DNA insertion. We have also analyzed plants that overexpress the protein encoded in chromosome 3. These plants have a different behavior respective to wild-type plants in the presence of copper and a copper chelator. In addition, overexpressing plants show higher production of reactive oxygen species than control plants. Sequences upstream of the translation start site of AtSCO1 were introduced in plants in front of the gus gene. Expression of the reporter gene was localized in meristematic tissues, anthers and embryos at different developmental stages. Our results suggest that AtSCO1 is essential during plant embryogenesis and may be involved in a signalling pathway related with the response of plants to stress and/or copper availability.