A Multidrug Resistance–Associated Protein Involved in Anthocyanin Transport in Zea mays

Abstract

Anthocyanin biosynthesis is one of the most thoroughly studied enzymatic pathways in biology, but little is known about the molecular mechanisms of its final stage: the transport of the anthocyanin pigment into the vacuole. We have identified a multidrug resistance-associated protein (MRP), ZmMrp3, that is required for this transport process in maize (Zea mays). ZmMrp3 expression is controlled by the regulators of anthocyanin biosynthesis and mirrors the expression of other anthocyanin structural genes. Localization of ZmMRP3 in vivo shows its presence in the tonoplast, the site at which anthocyanin transport occurs. Mutants generated using antisense constructs have a distinct pigmentation phenotype in the adult plant that results from a mislocalization of the pigment as well as significant reduction in anthocyanin content, with no alteration in the anthocyanin species produced. Surprisingly, mutant plants did not show a phenotype in the aleurone. This appears to reflect the presence of a second, highly homologous gene, ZmMrp4, that is also coregulated with the anthocyanin pathway but is expressed exclusively in aleurone tissue. This description of a plant MRP with a role in the transport of a known endogenous substrate provides a new model system for examining the biological and biochemical mechanisms involved in the MRP-mediated transport of plant secondary metabolites.

A Trafficking Pathway for Anthocyanins Overlaps with the Endoplasmic Reticulum-to-Vacuole Protein-Sorting Route in Arabidopsis and Contributes to the Formation of Vacuolar Inclusions

“…Whereas our results do not rule out the existence of other mechanisms for transport of anthocyanins to the vacuole, such as the interplay of GSTs and tonoplast transporters (Goodman et al, 2004), they highlight the existence of vesicular transport of anthocyanins with properties shared with the secretory pathway. Cellular, molecular, and genetic tools are becoming increasingly available in Arabidopsis to further dissect the mechanisms by which anthocyanins are transported and sequestered in the vacuole.…”

“…The existence of a vesicular-type transport of anthocyanins from the ER to the vacuole provides an alternative to models that involve AN9/BZ2-like GST carrier proteins and/or tonoplast transporters for the cytoplasmic and tonoplast trafficking of these compounds, respectively (Alfenito et al, 1998;Mueller et al, 2000;Mueller and Walbot, 2001;Goodman et al, 2004). Interestingly, whereas the tt19 mutation completely abolishes anthocyanin and PA accumulation (Kitamura et al, 2004), perturbing the formation or vacuolar uptake of GSH conjugates (GS-X) with CDNB or BSO or inhibiting ABC transporters with vanadate increases the number of AVIs (Fig.…”

“…cyanidin 3-glucoside) from the ER to the tonoplast (Mueller et al, 2000). Identification of the ZmMRP3 (maize tonoplast-localized multidrug resistance-associated protein), induced by the C1 and R anthocyanin regulators (Bruce et al, 2000), provides an additional player in a model involving carrier and transporter proteins in the trafficking of anthocyanins from the ER surface to the vacuole (Goodman et al, 2004). In Arabidopsis (Arabidopsis thaliana), mutants in TRANSPARENT TESTA19 (TT19) affect both anthocyanin accumulation in vegetative tissues and proanthocyanidin (PA) accumulation in seed coats.…”

ArabidopsisPEN3/PDR8, an ATP Binding Cassette Transporter, Contributes to Nonhost Resistance to Inappropriate Pathogens That Enter by Direct Penetration

“…In plants, ABC transporters have been localized to the tonoplast, mitochondria, chloroplasts, and plasma membrane (Kushnir et al, 2001;Moller et al, 2001;Goodman et al, 2004;Pighin et al, 2004). Recently, proteomic studies of different organelles have placed PEN3 in the plasma membrane, mitochondria, and chloroplasts (Brugiere et al, 2004;Kleffmann et al, 2004;Nü hse et al, 2004).…”

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

“…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.…”