A GENE PROPOSED TO ENCODE A TRANSMEMBRANE DOMAIN OF AN ABC TRANSPORTER IS EXPRESSED IN WHEAT MITOCHONDRIA

In a study of transcribed regions of the wheat mitochondrial genome, w e identified an open reading frame of 720 bp, which was consequently d esignated orf240. The amino acid sequence deduced from orf240 shows a high level of similarity with HelC, a protein essential for c-type cyt ochrome biogenesis in the photosynthetic purple bacterium Rhodobacter capsulatus. HelC is part of a purative heme ABC transporter. An open r eading frame homologous to orf240 is present in the mitochondrial geno me of Marchantia polymorpha. The wheat gene is expressed as an mRNA of 2.8 kb, which is further processed to smaller transcripts. The transc ript is highly edited, with 36 C to U modifications found in the codin g region of all cDNAs sequenced. RNA editing is responsible for change s in 14% of the amino acids specified by the transcript.