Mutation of CYCLOIDEA Expands Variation of Dorsal–ventral Flower Asymmetry Expressed as a Pigmentation Pattern in Torenia fournieri Cultivars

抄録

We investigated the molecular mechanisms underlying the pigmentation patterns of the dorsal petals in torenia (Torenia fournieri Lind. ex Fourn.) cultivars. ‘Piccolo Mix’ consists of lines exhibiting different pigmentation patterns in the limb of the dorsal petal, i.e., entirely pigmented (all-pigmented line), picotee with a pigmented margin (half-pigmented line), and entirely pale (pale line). In the all- and half-pigmented lines, expression of T. fournieri CYCLOIDEA2 (TfCYC2), which is involved in dorsal–ventral floral asymmetry, was inhibited by integration of Ty1/Copia-like LTR retrotransposon TORE2 into the exon of TfCYC2 (TfCYC2^TORE2). The all-pigmented line was homozygotic for TfCYC2^TORE2, while the pale line was homozygotic normal-type TfCYC2 (TfCYC2⁺). The half-pigmented line was heterozygotic TfCYC2^TORE2/TfCYC2⁺. Therefore, the extent of pigmentation of the dorsal petal is negatively correlated with the gene dosage of TfCYC2⁺. Further, ‘Crown Violet’, another torenia cultivar exhibiting the same pigmentation pattern as the all-pigmented line of ‘Piccolo Mix’, was also homozygotic for TfCYC2^TORE2. These results indicate that TfCYC2^TORE2 is responsible for the marked enrichment of flower pigmentation patterns seen in torenia cultivars.