Nucleotide sequence and transcriptional analysis of a mitochondrial plasmid from a cytoplasmic male-sterile line of sunflower.

A mitochondrial plasmid of 1,939 bp (P2) from a cytoplasmic male-sterile line of sunflower has been cloned and sequenced. It presents 437 bp of near-perfect homology to the 1.4-kb mitochondrial plasmid P1 from sunflower. Sequences homologous to P2 were found in nuclear DNA. P2 was transcribed into a major 980-nucleotide (nt) RNA molecule and two minor transcripts of 570 and 520 nt. They were all transcribed from the same strand and within the region nonhomologous to P1. A single 5' boundary and three 3' termini were determined for P2 transcripts. The 5' end is similar to a consensus sequence for plant mitochondrial genes. No evidence of translation products can be provided.