Cytoplasmic male sterility (CMS) in sunflower has been correlated with the expression of orf522, a chimeric mitochondria-l gene, generated by the insertion of exogenous genetic material, at the 3' side of the atpA locus. In order to investigate the role of the orf522 in CMS, we constructed a recombinant plasmid, suitable for transforming tobacco plants by particle gun methodol oS/. Several transformation events were obtained. Molecular analysis revealed that the orft22 gene is integrated into the nucleus. No integration events were observed in the mitochondrial (mt) genome. All the transgenic plants were fertile, suggesting that the orfr22 from sunflower does not confer male sterility in trânsgenic tobacco when expressed at the nuclear level.