Molecular characterization of the mutableflakedallele for flower variegation in the common morning glory

Abstract

SummaryThe 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.

Dynamics of mobile element activity in chalcone synthase loci in the common morning glory ( Ipomoea purpurea )

“…The 5Ј UTR differs in size among the alleles ranging from 813 bp to 2002 bp, whereas the introns vary in size from about 3 kb to Ϸ11 kb depending on the number and type of mobile element insertions. Sequence data from seven CHS-D alleles from I. purpurea collected in the southern Mexican states of Oaxaca, Chiapas, and Veracruz (four sequences) and in the southeastern United States (two sequences), together with a published sequence (29), are included in the analyses. Finally, we include a complete CHS-D sequence from a closely related species (I. nil) as an outgroup (1).…”

“…The identity includes not only the exons, but also the entire intron sequence and 1 kb of 5Ј UTR. The KKFR35N allele derived from a horticultural sample sequenced by Habu et al (29). The US1 allele was collected from a natural population in Georgia and described in Epperson and Clegg (34,35).…”

“…The presence of this element blocks the accumulation of transcript for CHS-D, preventing the production of pigment in the outer floral limb (21,18). Tip100 was described by Habu et al (29) in different alleles of I. purpurea (Fig. 3).…”

“…The Tip100 element is 3.9 kb with 11 bp terminal inverted repeats and an 8-bp target site duplication. The complete DNA sequence of the Tip100 element in the KKVR40 allele has been published (29), permitting an analysis of Tip100 evolutionary divergence between this allele and US1. One Tip100 is inserted at the identical site in the 5Ј end of the intron in all of the alleles shown in Fig.…”

“…In an allele (data not shown) where there is a footprint for the element in the 5Ј UTR location (indicating that the Tip100 has excised from this location), the flower exhibits high sectoring rates, suggesting high levels of somatic excision of the remaining element. In the KKWP3 allele, the two elements are in the opposite orientation to one another and the flower is stable white (29), suggesting a negligible level of excision. The two Tip100 elements in the US1 allele differ by a single nucleotide substitution, yielding an average pairwise Jukes-Cantor distance Fig.…”