Two genes encode the adenine nucleotide translocator of maize mitochondria

Abstract

Southern blot hybridisation of maize (Zea mays) genomic DNA with a specific cDNA probe and sequence analysis of several cDNAs have revealed that the mitochondrial adenine nucleotide translocator (ADP/ATP carrier) is encoded by two genes, both of which are expressed in dark‐grown coleoptile tissue. The structural genes (designated ANT‐G1 and ANT‐G2), encoding the two translocator polypeptides, have been isolated from a maize genomic library and characterised by DNA sequence analysis, mung bean nuclease mapping and primer extension. The two genes each contain two introns and encode very similar proteins. Transcripts from both genes have long (approximately 200 nucleotides) 5′ untranslated leaders which are unusual in that they contain several ATG codons upstream of the initiation codon. Transcript analysis of RNA extracted from serial sections of developing maize leaves reveals that the translocator genes are most actively transcribed in the basal meristem, while transcripts were undetectable in green leaves.