Physical and gene mapping of cauliflower (Brassica oleracea) mitochondrial DNA

Abstract

A physical map of the mitochondrial DNA isolated from B. oleracea (cauliflower) inflorescences was constructed with the restriction endonucleases Sall, Kpnl and Bgll. Physical mapping was made using the multi enzyme method with either unlabeled or labeled DNA fragments isolated by preparative electrophoresis and a clone bank prepared by inserting incomplete Sall restriction digests of mitochondrial DNA into a cosmid vector. The different mapping studies led to a circular map, about 217 kb in size, containing the entire sequence complexity of the genome. The 26S and 18S – 5S ribosomal RNA genes appeared to be separated by about 75 kb in this map. However, the particular cross-hybridization between several restriction fragments and the sequential diversity of some cosmids indicated that intra molecular recombination may occur naturally in higher plant mitochondria. Namely, one recombinational event resulted in the ribosomal RNA genes mapping closer together.