title: MATE2 mediates vacuolar sequestration of flavonoid glycosides and glycoside malonates in Medicago 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 3'-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.
authors.affiliation: Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhao
authors.forename: David
authors.initials: D
authors.lastname: Huhman
authors.forename: Gail
authors.initials: G
authors.lastname: Shadle
authors.forename: Xian-Zhi
authors.initials: XZ
authors.lastname: He
authors.forename: Lloyd W
authors.initials: LW
authors.lastname: Sumner
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Tang
authors.forename: Richard A
authors.initials: RA
authors.lastname: Dixon
mesh_terms: D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D053898:Biosynthetic Pathways; D004721:Endoplasmic Reticulum / Q000201:enzymology; D005419:Flavonoids / Q000378:metabolism*; D035264:Flowers / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D006027:Glycosides / Q000378:metabolism*; D007700:Kinetics; D008314:Malonates / Q000378:metabolism*; D046913:Medicago truncatula / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D008861:Microsomes / Q000378:metabolism; D009928:Organ Specificity / Q000235:genetics; D010802:Phylogeny; D010858:Pigmentation; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D044945:Proanthocyanidins / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D012639:Seeds / Q000378:metabolism; D013379:Substrate Specificity; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D005419:Flavonoids; D006027:Glycosides; D008314:Malonates; D010940:Plant Proteins; D044945:Proanthocyanidins; C013221:proanthocyanidin; D000217:Acyltransferases