Daminozide reduces red color intensity in herbaceous peony (Paeonia lactiflora Pall.) flowers by inhibiting the expression of flavonoid biosynthetic genes

Abstract

Daminozide is a plant growth retardant that inhibits 2-oxoglutarate-dependent dioxygenase activity in the gibberellin biosynthesis pathway, but few studies have focused on its effect on the flavonoid biosynthesis pathway involved in flower color. In the present study, the effect of daminozide on the regulation of flower color was investigated. An herbaceous peony (Paeonia lactiflora Pall.) cultivar 'Fenzhu Pan' was used as the material and treated with daminozide. Color parameters of petals were measured; flavonoid composition and content as well as flavonoid biosynthetic gene expression were monitored. The results showed that daminozide treatment caused less red coloration in herbaceous peony. The content of total anthocyanins was decreased by 23%, and the content of total anthoxanthins was increased by 8%; thus, it appeared that less red coloration in daminozide-treated flowers was associated with restricted anthocyanin accumulation. Furthermore, the gene expression patterns of flavonoid 3'-hydroxylase, dihydroflavonol 4-reductase and anthocyanidin synthase were lower after daminozide treatment, which could decrease anthocyanin accumulation and lead to less red coloration in flowers. These findings would improve our understanding of daminozide regulation of flower color in herbaceous peony.

Keywords: Daminozide; Flavonoids; Gene expression; Herbaceous peony.

Fig. 1

Flowers of herbaceous peony in the control and daminozide-treated groups during flower development. S1 (Stage 1) = flower-bud stage, S2 (Stage 2) = initiating bloom stage, S3 (Stage 3) = bloom stage

Fig. 2

Color parameters of herbaceous peony in the control and daminozide-treated petals during flower development. S1 (Stage 1) = flower-bud stage, S2 (Stage 2) = initiating bloom stage, S3 (Stage 3) = bloom stage. The values represented mean ± SE, and different letters marked significant differences (p < 0.05)

Fig. 3

HPLC chromatograms of herbaceous peony in the control and daminozide-treated petals in S1 (Stage 1 = flower-bud stage). a Anthocyanins, detected at 525 nm; b Anthoxanthins, detected at 350 nm; a1–a3 indicate identified anthocyanins; f1–f7 indicate identified anthoxanthins

Fig. 4

Simplified schematic overview of the major flavonoid biosynthetic pathway in herbaceous peony petals and the contents of tentative flavonoid compounds in the control and daminozide-treated petals during flower development. The values represented mean ± SE, and different letters marked significant differences (p < 0.05)

Fig. 5

Total anthocyanin, anthoxanthin and flavonoid content of herbaceous peony in the control and daminozide-treated petals during flower development. S1 (Stage 1) = flower-bud stage, S2 (Stage 2) = initiating bloom stage, S3 (Stage 3) = bloom stage. The values represented mean ± SE, and different letters marked significant differences (p < 0.05)

Fig. 6

Flavonoid biosynthetic gene expression analysis of herbaceous peony in the control and daminozide-treated petals during flower development. S1 (Stage 1) = flower-bud stage, S2 (Stage 2) = initiating bloom stage, S3 (Stage 3) = bloom stage. The values represented mean ± SE, and different letters marked significant differences (p < 0.05)