Role in Phenylpropanoid Biosynthesis of the Grapevine Plastidic Phosphoenolpyruvate Translocator VviPPT1

Abstract Phosphoenolpyruvate (PEP), the main precursor of the shikimate pathway in the plastids, is imported from the cytosol through a PEP translocator (PPT). The final product of the shikimate pathway, chorismate, is the precursor for all three aromatic amino acids (AAAs), which are pivotal not only in the production of proteins but as precursors of several primary and secondary metabolites. In this study, pigmented cultured cells from cv Gamay fréaux grapes were used as a model to investigate the role of the plastidal VviPPT1 in grapevine secondary metabolism. CRISPR/Cas9-mediated knockout of VviPPT1 produced a cell line with an obvious visual low anthocyanin phenotype. Besides evident modifications of the metabolome, such as a strong reduction in phenolic acids, flavonols, and stilbenoids, key enzymes of the shikimate and phenylpropanoid pathways were inhibited at the protein activity and/or gene expression level, revealing a complex regulation of secondary metabolism not only dependent on the observed reduction of phenylalanine.