Stockmeyer, Kerstin

Kempken, Frank

Pring, Daryl

Unique chimeric mitochondrial genes are associated with cytoplasmic male sterility (CMS) in many higher plants. It is thought that disruption in pollen development is a consequence of mitochondrial dysfunction associated with these chimeric genes. The IS1112C source of Sorghum bicolor CMS contains the chimeric mitochondrial open reading frame orf107, which exclusively is present in that cytoplasm. To analyse the effect of a chimeric mitochondrial gene on mitochondrial gene expression and pollen development, we introduced the CMS-associated mitochondrial orf107 from S. bicolor into the Arabidopsis thaliana nuclear genome and expressed it, by the use of different flower-, or anther-specific promoters. The functionality and specificity of these promoters was demonstrated through histochemical GUS-staining. Expression of ORF107 was analysed by RT-PCR and biotinylation. Mitochondrial import was confirmed employing GFP-fusion experiments. Constitutive as well as flower-specific expression of orf107 fused to the yeast coxIV mitochondrial inner membrane targeting presequence or the Nicotiana plubaginifolia atp2-1 matrix-targeting signal revealed no deleterious effect on pollen development. T1 plants from primary transformants also showed normal pollen development. These data suggest that there is no effect of the ORF107 protein on male fertility in A. thaliana.

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