COMPARISON OF THE RESTRICTION ENDONUCLEASE DIGESTION PATTERNS OF MITOCHONDRIAL DNA FROM NORMAL AND MALE STERILE CYTOPLASMS OF ZEA MAYS L

Kathleen S. Borck ¹ and Virginia Walbot ¹

¹ Department of Biological Sciences, Stanford University, Stanford, California 94305-2493

High resolution gel electrophoresis has allowed the assignment of fragment number and molecular weight to EcoRI, SalI and PstI restriction fragments of mitochondrial DNA from B37 normal (N) and B37 T, C and S male sterile cytoplasmic types of maize. A minimum complexity of 450-475 kb has been established. Hybridization of cloned EcoRI fragments to restriction digests of total mitochondrial DNA suggests that at least 80% of the genome is composed of unique sequences. Restriction fragments of identical size in N, T, C and S contain similar sequence information as evidenced by their hybridization behavior.—The total SalI digest and the larger PstI fragments representing 80% of the total complexity were used to calculate the fraction of shared fragments of each pairwise combination of cytoplasmic types. The C type mtDNA is most closely allied with the other mtDNAs and shares 67% of fragments with S, 65% with N, and 60% with T. The S type mtDNA is quite divergent from N (53% shared fragments) and T (56% shared fragments). N and T share 59% of the fragments. These results are discussed in terms of the origin of mtDNA diversity in maize.