Molecular characterization of a brown midrib3 deletion mutation in maize

The caffeic acid O-methyltransferase (COMT) gene plays an important role in the synthesis of lignin. We have used the polymerase chain reaction in conjuction with genomic analysis to characterize deletion mutations of this gene in maize. In addition, we have analyzed and compared regions of the COMT gene from three distinct heterotic groups. Both PCR and Southern analysis indicate that the active wild-type COMT gene can be polymorphic. We suggest that the intron domain of at least one heterotic inbred can contribute to the alteration of the wild-type gene. In addition, multiple deletion mutations have occurred at this locus. We have found a previously uncharacterized deletion mutation in which segments of both the intron and exon have been deleted and replaced by other sequences. Precise knowledge of its sequence has allowed us to develop an assay by which we can follow this mutation in a breeding program.