Transcriptional and metabolite profiling analyses uncover novel genes essential for polyphenol accumulation

Significant advances in basic sciences are frequently driven by novel technologies. This is also true for research on polyphenols which are major plant secondary metabolites of extremely diverse structures that have many functions in plants and humans. This chapter reports the detection of novel genes putatively involved in the formation of polyphenols in strawberry (Fragaria?×?ananassa) by transcriptome and metabolite profiling analysis. One of the genes (FaPRX27) was validated by heterologous expression and functional characterization, which highlighted the competition of the different phenolics pathways for their common precursors. Through reverse genetic analysis of the functions of four additional candidate genes, six acylphloroglucinol (APG)-glucosides were discovered as native Fragaria spp. fruit metabolites. It could be shown that Fragaria spp. plants have the potential to synthesize pharmaceutically important APGs using dual functional chalcone/(phloriso)valerophenone synthases that are expressed during fruit ripening. Additionally, ripening-related glucosyltransferase genes (UGTs) were characterized by comprehensive biochemical analyses of the encoded proteins and by a RNA interference approach. Metabolite analyses of transgenic fruits confirmed UGT71K3 as a UDP-glucose:APG glucosyltransferase in planta. These results provide the foundation for the breeding of fruits with improved health benefits and for the biotechnological production of bioactive natural products.