Figure 2.

Hypothetical scheme of flavonoid transport pathways in grapevine. Flavonoids could be conjugated with glutathione (GSH) through a reaction catalysed by glutathione S-transferases (GSTs). The main transporters localized in grapevine vacuole and plasma membrane are the ATP-binding cassette (ABC) proteins and the bilitranslocase-homologue (BTL-homologue). The multidrug and toxic compound extrusion (MATE) protein, shown to be involved in flavonoid transport in other plant species, has also been added. Transport mediated by vesicle trafficking is indicated by circles (AVIs, anthocyanic vacuolar inclusions; ACPs, anthocyanoplasts). Question marks indicate the lack of information or still hypothetical components and steps in the process.