Mitochondrial DNA changes in abnormal growth (nonchromosomal stripe) mutants of maize

Abstract

The genetic analysis of higher plant mitochondria has been limited by a scarcity of identified mutations with known progenitors. Correspondingly, few molecular studies have been directed at types of plant mitochondrial variation other than cytoplasmic male sterility. The maternally inherited nonchromosomal stripe (NCS) mutants of maize have profound deleterious effects on plant growth and yield. We report specific alterations in mitochondrial DNA (mtDNA) for two independent, phenotypically distinct NCS mutants. NCS2 plants have a distinctive 21-kilobase Xho I mtDNA band and very reduced amounts of DNA in an 8-kilobase band that is present in the progenitor. NCS3 plants have a distinctive 20-kilobase Xho I band and a reduction in a 16-kilobase band. Our studies confirm that the affected organelle in NCS plants is the mitochondrion. Because NCS-type plants appear with a certain frequency in a particular line (WF9), this line is a potential source of additional mutations for functional and molecular analyses of maize mitochondrial genes.