MATE Transporters Facilitate Vacuolar Uptake of Epicatechin 3′-O-Glucoside for Proanthocyanidin Biosynthesis inMedicago truncatulaandArabidopsis   

Abstract

Expression of the Arabidopsis thaliana MYB transcription factor TRANSPARENT TESTA 2 (TT2) in Medicago trunculata hairy roots induces both proanthocyanidin accumulation and the ATP-dependent vacuolar/vesicular uptake of epicatechin 3′-O-glucoside; neither process is active in control roots that do, however, possess anthocyanidin 3-O-glucoside vacuolar uptake activity. A vacuolar membrane-localized multidrug and toxic compound extrusion (MATE) transporter, Medicago MATE1, was identified at the molecular level and shown to preferentially transport epicatechin 3′-O-glucoside. Genetic evidence has implicated TT12, a tonoplastic MATE transporter from Arabidopsis, in the transport of precursors for proanthocyanidin biosynthesis in the seed coat. However, although Arabidopsis TT12 facilitates the transport of cyanidin 3-O-glucoside into membrane vesicles when expressed in yeast, there is no evidence that cyanidin 3-O-glucoside is converted to proanthocyanidins after transport into the vacuole. Here, we show that Arabidopsis TT12, like Medicago MATE1, functions to transport epicatechin 3′-O-glucoside as a precursor for proanthocyanidin biosynthesis, and Medicago MATE1 complements the seed proanthocyanidin phenotype of the Arabidopsis tt12 mutant both quantitatively and qualitatively. On the basis of biochemical properties, tissue-specific expression pattern, and genetic loss-of-function analysis, we conclude that MATE1 is an essential membrane transporter for proanthocyanidin biosynthesis in the Medicago seed coat. Implications of these findings for the assembly of oligomeric proanthocyanidins are discussed.

Draft genome sequence of chickpea (Cicer arietinum) provides a resource for trait improvement

“…Among the 0.7% of the genome with Tajima's D < −2 is a region of Ca4 that contains a tandem array of three co-orthologs of the MATE family transporter TT12. The M. truncatula ortholog of TT12 functions in condensed tannin formation, which results in pigmented seeds 25 . This signature of purifying selection was evident in dark-colored desi but not light-colored kabuli genotypes, consistent with ongoing purifying selection for seed color.…”

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.…”

“…The simultaneous addition of ABC transporter and V-ATPase inhibitors inhibited the ABA-GE uptake below the levels observed for these compounds individually. Orthovanadate and bafilomycin A1 were used at concentrations shown to completely inhibit corresponding enzymatic activity in tonoplast preparations (Frelet-Barrand et al, 2008;Zhao and Dixon, 2009). The presence of the preexisting proton gradients in isolated vacuoles explains why the combination of bafilomycin A1 with NH 4 Cl decreased the ABA-GE uptake more than bafilomycin A1 alone.…”

“…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).…”

MYB5 and MYB14 Play Pivotal Roles in Seed Coat Polymer Biosynthesis in Medicago truncatula

“…epicatechin) by anthocyanidin reductase (ANR; Xie et al, 2003Xie et al, , 2004. Epicatechin can also be glycosylated and then transported to the vacuole by a multidrug and toxic compound extrusion transporter (Pang et al, 2008;Zhao and Dixon, 2009), where it is believed to be polymerized by a laccase to form PA oligomers (Pourcel et al, 2005).…”