Functional analysis of flavonoid 3’,5’-hydroxylase gene using transgenic Japanese morning glory (Ipomoea nil)

Delphinidin (Dp), an anthocyanin, is a blue and purple pigment present in many flowers of high economic value in ornamental horticulture.
However, some ornamental species, such as chrysanthemums, lilies, roses, and carnations, lack the flavonoid 3’,5’-hydroxylase (F3’5’H) gene involved in delphinidin biosynthesis and, therefore, lack Dp and do not have blue-flowered cultivars.
Recently, F3’5’H genes have been isolated from plants with blue and purple flowers that accumulate Dp and the transgenic plants expressing this gene have been produced.
However, compatibility exists between the exogenous F3’5’H genes and the host plant, making the Dp accumulation trait plant specific.
For example, the introduction of Campanula medium F3’5’H into chrysanthemums produced plants with high Dp accumulation, whereas F3’5’H from other plants, such as Gentiana triflora, resulted in reduced Dp accumulation.
Several studies on roses have also reported similar compatibility.
In this study, we used Ipomoea nil, which lacks the F3’5’H gene, to clarify the mechanisms underlying the compatibility between the F3’5’H gene and the host plant.
Compared with chrysanthemums and roses, I. nil has advantages such as high efficiency in genetic transformation and a short interval between the transformation and flowering of regenerated plants.
The accumulation of Dp-type anthocyanins was high when F3’5’H genes isolated from Eustoma grandiflorum, C. medium, and × Viola wittrockiana were introduced into I. nil but low when the gene was from G. triflora. Unexpectedly, the petals of Dp-accumulated transgenic plants did not develop adequately, and the buds did not open.
Observations of petal cells revealed that enlargement, necessary for flowering, was inhibited.
In conclusion, this study revealed that the transgenic I. nil is valuable for the functional analysis of the F3’5’H gene.

IV Asian Horticultural Congress – AHC2023

T.P. Huynh, C. Motoyama, H. Oshima, N. Kozai, F. Hashimoto, K. Shimizu

Agrobacterium, anthocyanin, biosynthesis, Campanula, Eustoma, flower, pigment

https://doi.org/10.17660/ActaHortic.2024.1404.117