Transcription factor mediated control of anthocyanin biosynthesis in vegetative tissues

Plants accumulate secondary metabolites to adapt to environmental conditions. These compounds, here exemplified by the purple coloured anthocyanins, are accumulated upon high temperatures, UV-light, drought and nutrient deficiencies, and may contribute to tolerance to these stresses. Producing compounds is often part of a more broad response of the plant to changes in the environment. Here we investigate how a transcription-factor mediated program for controlling anthocyanin biosynthesis also has effects on formation of specialized cell structures and changes in the plant root architecture. A systems biology approach was developed in tomato for coordinated induction of biosynthesis of anthocyanins, in a tissue- and development independent manner. A transcription factor couple from Antirrhinum that is known to control anthocyanin biosynthesis was introduced in tomato under control of a dexamethasone-inducible promoter. By application of dexamethasone, anthocyanin formation is induced within 24h in vegetative tissues and in undifferentiated cells. Profiles of metabolites and gene expression were analysed in several tomato tissues. Changes in concentration of anthocyanins and other phenolic compounds were observed in all tested tissues, accompanied by induction of the biosynthetic pathways leading from glucose to anthocyanins. A number of pathways were observed to be regulated that are not known to be involved in anthocyanin biosynthesis. Anthocyanin-producing plants displayed profound physiological and architectural changes, depending on the tissue, including root branching, root epithelial cell morphology, seed germination and leaf conductance. The inducible anthocyanin-production system reveals a range of phenomena that accompany anthocyanin biosynthesis in tomato, including adaptions of the plants architecture and physiology.