MATE2 Mediates Vacuolar Sequestration of Flavonoid Glycosides and Glycoside Malonates inMedicago truncatula     

Abstract

The majority of flavonoids, such as anthocyanins, proanthocyanidins, and isoflavones, are stored in the central vacuole, but the molecular basis of flavonoid transport is still poorly understood. Here, we report the functional characterization of a multidrug and toxin extrusion transporter (MATE2), from Medicago truncatula. MATE 2 is expressed primarily in leaves and flowers. Despite its high similarity to the epicatechin 39-O-glucoside transporter MATE1, MATE2 cannot efficiently transport proanthocyanidin precursors. In contrast, MATE2 shows higher transport capacity for anthocyanins and lower efficiency for other flavonoid glycosides. Three malonyltransferases that are coexpressed with MATE2 were identified. The malonylated flavonoid glucosides generated by these malonyltransferases are more efficiently taken up into MATE2-containing membrane vesicles than are the parent glycosides. Malonylation increases both the affinity and transport efficiency of flavonoid glucosides for uptake by MATE2. Genetic loss of MATE2 function leads to the disappearance of leaf anthocyanin pigmentation and pale flower color as a result of drastic decreases in the levels of various flavonoids. However, some flavonoid glycoside malonates accumulate to higher levels in MATE2 knockouts than in wild-type controls. Deletion of MATE2 increases seed proanthocyanidin biosynthesis, presumably via redirection of metabolic flux from anthocyanin storage.

Vacuolar Transport of Abscisic Acid Glucosyl Ester Is Mediated by ATP-Binding Cassette and Proton-Antiport Mechanisms in Arabidopsis

“…The anthocyanin malvidin-3-O-glucoside is transported into vacuoles of grape (Vitis vinifera) berries by the ABCC transporter ABCC1 from grape (Francisco et al, 2013). Proton gradient-dependent vacuolar transport mechanisms were reported for diverse flavonoid glucosides (Klein et al, 1996;Frangne et al, 2002;Zhao and Dixon, 2009;Zhao et al, 2011). Moreover, the vacuolar import mechanism of particular Glc conjugates was found to be species or tissue specific.…”

“…Members of the MATE transporter superfamily have been shown to mediate the proton-dependent vacuolar sequestration of flavonoid glucosides (Marinova et al, 2007;Zhao and Dixon, 2009;Zhao et al, 2011). In Arabidopsis, the MATE superfamily consists of 56 members (The Arabidopsis Genome Initiative, 2000).…”

Manoyl Oxide (13R), the Biosynthetic Precursor of Forskolin, Is Synthesized in Specialized Root Cork Cells in Coleus forskohlii

“…These metabolites may otherwise display adverse activities for the producing plant cell. Intracellular storage of such biologically active metabolites in the vacuole is well established for water-soluble compounds and for compounds that become water soluble through conjugation (Marinova et al, 2007;Ferreres et al, 2011;Zhao et al, 2011;Li et al, 2012b). Similarly, for the large class of often-lipophilic terpenoids, it has been suggested that their intracellular accumulation may be limited by nonspecific interference with cellular Figure 6.…”

ABCC1, an ATP Binding Cassette Protein from Grape Berry, Transports Anthocyanidin 3-O-Glucosides

“…When expressed in barrel medic (Medicago truncatula) hairy roots (HRs), Arabidopsis TT12 as well as a MATE transporter of barrel medic, MATE1, transport the proanthocyanidin (PA) precursor epichatechin 3-Oglucoside (Zhao and Dixon, 2009). A second barrel medic MATE transporter, MATE2, was shown to have consistently different substrate specificity despite its high similarity to MATE1; it efficiently catalyzes the vacuolar uptake of malonylated anthocyanins, while transporting glycosylated anthocyanidins at a lower rate (Zhao et al, 2011). More recently, two grapevine (Vitis vinifera) MATEs, AM1 and AM3, have been described to specifically transport acylated anthocyanins, but not glucosylated ones, which are the predominant forms that accumulate in berries of most red grapevine cultivars .…”

“…Concerning the transporter-mediated model, biochemical, molecular, and genetic evidence support the involvement of both multidrug and toxic extrusion (MATE) and the ATP binding cassette (ABC) proteins in the transport of anthocyanins (Goodman et al, 2004;Marinova et al, 2007b;Gomez et al, 2009;Zhao and Dixon, 2009;Zhao et al, 2011). MATE transporters comprise a large family of transporters, widely distributed in all living organisms.…”