Flavonoids, common to all land plants, are synthesized via the phenylpropanoid pathway. Phenylalanine ammonia lyase catalyzes the first reaction of this pathway (conversion of phenylalanine to cinnamate), which is followed by a set of about ten enzymes catalyzing reactions to flavones, flavonols and anthocyanins (Fig.1). Anthocyanin pigments are responsible for pink, orange and purple to blue colors in petals.
Flavonoids in our model ornamental plant Gerbera hybrida consist of three subgroups, flavones, flavonols and anthocyanins. Most of the anthocyanins accumulate in the adaxial epidermi of petals and give the different cultivars their different color. Both pelargonidin and cyanidin derivatives are found in gerbera, but none of the cultivars contain delphinidin.
According to chromatographic and MS analysis for ray flowers of more than 22 cultivars in different developmental stages, we observed that pelargonidin-type Gerbera cultivars accumulated only the favone apigenin, while cyanidin-type cultivars accumulated luteolin. However, the biosynthesis of flavonols was different, quercetin was observed in both pelargonidin and cyanidin-type cultivars.
Based on chemical analysis, RNA sequencing and enzyme assays, we are trying to understand the biosynthetic pathway of flavonoids in differentGerbera cultivars. Different aspects in the timing of gene expression encoding isoenzymes e.g. F3’H and DFR across developmental stages seems important for determination of the flavonoid pattern in the inflorescence
