DNA rearrangements at the region of the dihydroflavonol 4-reductase gene for flower pigmentation and incomplete dominance in morning glory carrying the mutable flaked mutation

 The a-3 ^flecked J] variegated line of Japanese morning glory bearing white flowers with normal-colored flecks and sectors has been shown to carry a 6.4-kb transposable element, Tpn1, inserted within the DFR-B gene, one of the anthocyanin biosynthesis genes encoding dihydroflavonol 4-reductase (DFR). The a ^flaked M] variegated line of morning glory also bears white flowers with normal-colored flakes and sectors, and it was shown to carry multiple DNA rearrangements, including insertions of mobile element-like sequences, MELSIP1 and MELSIP2, in its DFR gene region. Unlike the a-3 ^flecked J] mutation, the mutable a ^flaked M] allele exhibited incomplete dominance. Interestingly, not only intensely colored flakes but also white spots and sectors were often observed in lightly colored flowers of morning glory in the heterozygous state AM]/a ^flaked M]. The interspecific F₁ hybrids between Japanese morning glory and morning glory carrying both a-3 ^flecked J]/A-3M] and AJ]/ a ^flaked M] in the heterozygous condition bear lightly colored flowers with intensely colored sectors as well as white flakes. The results clearly demonstrated that the DFR gene in the a ^flaked M] line of morning glory is active and complements the DFR-B gene carrying Tpn1 in the a-3 ^flecked J] line of Japanese morning glory. Interspecific allelic interactions between the mutable a ^flaked M] gene of morning glory and the corresponding wild-type AJ] gene of Japanese morning glory resulted in incomplete dominance and the formation of white flakes and sectors. The appearance of the white flakes may be due to a somatic mutation of the AJ] gene. Received: 4 November 1996/Accepted: 13 December 1996