A mitochondrial transcript with homology to the 3′ end of the chloroplast psbA gene is present only in the atrazine-resistant biotype of Chenopodium album.

The 3' end of the chloroplast (ct) psbA gene is present in the mitochondrial genome of Chenopodium album and is expressed in mitochondria from atrazine-resistant plants. Short specific chloroplast psbA gene probes reveal a 270 bp homolog with the 3' end of the chloroplast psbA gene. The homology starts close to the codon 264 of this gene; this codon is known to be involved in atrazine resistance when mutated in the chloroplast DNA. Comparison of susceptible and resistant plants has not given evidence of modification in the mitochondrial (mt) genome; however, the homologous 3' end of the ct psbA gene present in the mitochondria is expressed as part of a 0.8 kb transcript only in atrazine-resistant plants and not in susceptible ones.