We screened the Arabidopsis cDNA library toidentify functional suppressors of AtBI-1, a gene that suppressescell death induced by Bax gene expression in yeast. Cdf 3encodes a 18-amino-acid protein with a molecular mass of25 kDa. This protein has two uncharacterized domains atamino acids residues 5-64 and 74-117. In the present study,CDF3 was found to induce growth defects in yeast andarrested yeast growth, although the cell-growth defect wassomewhat les than that of Bax. Its localization in the innermitochondria was esential for suppresion of yeast-celproliferation. The morphological abnormality of the intracellularnetwork, which is a halmark of AtBI-1, was atenuated byCdf 3 expression.