The C1 locus in maize (Zea mays L.):: effect on gene expression

The focus of this genetic study is on the expression of two wild-type alleles [Wisconsin (W22 C) and Cornell (Cornell)] at the C1 locus, functioning in their color-producing roles, that can be distinguished by assaying the gene expression in their competitive capacity against a third allele at that locus. The third allele is a transposon-induced color-suppressing allele with a deficiency that suppresses anthocyanin color. This color suppressing allele (C1-l Delta), however, is not as fully potent as the standard color suppressing allele C1-I (std) and, thus, is competed more readily against the C1 allele in the regulatory control of anthocyanin coloration. Both the C1-l Delta and CI-I(std) alleles have somewhat similar deficiencies and produce truncated transcripts. In the measurement of anthocyanin production in heterozygote genotypes of the two wild-type alleles against the C1-l Delta color suppressor, the following could be shown genetically: that the inhibitor allele reduces color; the two wild-type alleles are different in their competitive capacity against CI-IA; and the genetic background of the two lines influences the degree of color expression. A hypothesis is presented that this study provides a genetic demonstration of the competition for transcription sites on the promoter between two different wild-type alleles that does lead to differences in gene expression. Further, this study illustrates how a genetic investigation could uncover subtle differences among seemingly similar wildtype alleles.