Molecular characterization of the mutable flaked allele for flower variegation in the common morning glory

The mutable flaked (or a(f)) lines of the common morning glory bear white flowers with colored flakes and sectors. The a(f) allele shows incomplete dominance. Plants in the heterozygous state A/a(f) bear lightly colored flowers with intensely colored flakes and occasionally with white sectors. We showed that the mutable a(f) allele is caused by insertion of a new transposable element, Tip100, into the CHS-D gene intron. Tip100 is 3.9 kb long and belongs to the Ac/Ds family. Although the timing and frequency of the flower variegation vary in different lines, they carry an identical mutable allele. We also noticed that a flaked subline, bearing variegated flowers, carries a Tip100 derivative, Tip100-1 The structure of Tip100-1 contains an additional 48 bp terminal sequence as tandem repeats and its integration site is identical to that of Tip100. Another line, with stable white flowers, is a double mutant carrying two copies of Tip100 in the CHS-D gene. These results are discussed with regard to the variegated phenotypes of flowers in various mutable lines.