A bud sport from a bicolored carnation to a single-colored carnation is accompanied by low expression levels of cinnamoyl-CoA reductase-like genes

摘要

In continuously bud-sported carnation cultivars, namely the 'MINAMI series', 'Feminine Minami' (single deep pink-colored flower) was established by the spontaneous mutation of 'Orange Minami' (bicolored flower; the distal and proximal parts of the petals are pink and yellowish orange, respectively). To clarify the mechanisms of the bud sport, flavonoid amounts and expression levels of flavonoid biosynthesis-related genes were investigated in distal and proximal parts of the petals. These investigations were based on the hypothesis that the substrate availability for flavonoid biosynthesis was limited by the alternative upstream metabolic pathway, which branched from the flavonoid biosynthetic pathway. Thus, we isolated three cinnamoyl-CoA reductase-like genes [CRL1, CRL2 and CRL3), and investigated the expression levels of CRLs. The results indicated that the expression levels of CRL1/2 in the distal part of'Orange Minami' petals and the whole petal of'Feminine Minami' were remarkably lower, but remained high in the proximal part of 'Orange Minami'. The expression level of CRL3 did not differ between the two cultivars. The results of this study suggest that suppression of CRL1/2 expression in the petals of 'Orange Minami' by a bud sport can lead to a reduction of substrate amounts for monolignol biosynthesis and a subsequent increase in flavonoids resulting in the flower phenotype of'Feminine Minami'.