Low-light intensity reprogramed flower pigmentation in Dendrobium Sonia via downregulation of dihydroflavonol 4-reductase and anthocyanidin synthase genes

Abstract

Flower color is an important trait of orchids that extensively influences consumer-purchasing decisions, and thus manipulation of flower color variation is a way for orchid production to provide more options to consumers. The application of net shading is one of the simplest methods for transformation of an original orchid flower color. In this study, we report the first color modification of the commercial Dendrobium Sonia (Ds) flower through a simple light intensity adjustment by the application of net shading. A reduction of light intensity significantly decreased anthocyanin production in all stages of flower development, leading to a paler purple. The expression profiles of six flower-color associated genes, including chalcone synthase, DsCHS; chalcone isomerase, DsCHI; flavanone 3-hydroxylase, DsF3H; dihydroflavonol 4-reductase, DsDFR; anthocyanidin synthase, DsANS; and flavonol synthase, DsFLS in three flower stages (very young bud, mature bud, and fully open flower) developing under typical-light (240 μmol photons m−2 s−1) and low-light (45 μmol photons m−2 s−1) intensities were investigated. The lighter flower color produced under the low-light treatment correlated with downregulation of DsDFR and DsANS expression, while the early anthocyanin biosynthetic genes, including DsCHS, DsCHI, DsF3H, and DsFLS, were not significantly affected. This indicates that the expression of DsDFR and DsANS in D. Sonia is light dependent, while the expression of DsCHS, DsCHI, DsF3H, and DsFLS is light independent. Therefore, this low-light transformed flower color is not genetically modified but is economically and socially acceptable, and also nature- and environment-friendly. This finding will be useful for future applications with other Dendrobium species to produce flower color shade variation.