Review Impact of biochemical pre-studies on specific metabolic engineering strategies of flavonoid biosynthesis in plant tissues

The role of flavonoids including anthocyanins in providing brilliant and coloured pigments in different plant tissues, their contribution to plant protection against UV-B radiation, microbial and herbivory pathogens and their medicinal and nutritional value is well documented. Furthermore, general and manifold studies led to the accumulation of a vast amount of knowledge on genetics, chemistry, biochemistry and molecular biology of this pigment group. Several expensive and time consuming experiments were performed to introduce or suppress specific flavonoid genes in ornamental plants. For an improvement of such metabolic engineering strategies a careful characterisation of the target plants and the genes of interest is highly recommended. From simple chemical and biochemical studies with well-established methods valuable information on the gene pool, the biosynthetic pathway, the substrate specificity of relevant enzymes of concerned steps can be easily obtained, allowing a prediction of the putative resulting phenotype of the planned experiment. Actual studies were performed with Zantedeschia, Lilium and Osteospermum using supplementation experiments, inhibitor application, heterologous gene expression and enzymological assays with plant protein extracts and recombinant proteins to design new powerful strategies to modify the flavonoid pattern in these plants, leading to new flower colours