The Pdr12 ABC transporter is required for the development of weak organic acid resistance in yeast

Abstract

P.Piper and Y.Mahé contributed equally to this workExposure of Saccharomyces cerevisiae to sorbic acid strongly induces two plasma membrane proteins, one of which is identified in this study as the ATP-binding cassette (ABC) transporter Pdr12. In the absence of weak acid stress, yeast cells grown at pH 7.0 express extremely low Pdr12 levels. However, sorbate treatment causes a dramatic induction of Pdr12 in the plasma membrane. Pdr12 is essential for the adaptation of yeast to growth under weak acid stress, since Δpdr12 mutants are hypersensitive at low pH to the food preservatives sorbic, benzoic and propionic acids, as well as high acetate levels. Moreover, active benzoate efflux is severely impaired in Δpdr12 cells. Hence, Pdr12 confers weak acid resistance by mediating energydependent extrusion of water-soluble carboxylate anions. The normal physiological function of Pdr12 is perhaps to protect against the potential toxicity of weak organic acids secreted by competitor organisms, acids that will accumulate to inhibitory levels in cells at low pH. This is the first demonstration that regulated expression of a eukaryotic ABC transporter mediates weak organic acid resistance development, the cause of widespread food spoilage by yeasts. The data also have important biotechnological implications, as they suggest that the inhibition of this transporter could be a strategy for preventing food spoilage.

On the Mechanism of Constitutive Pdr1 Activator-mediated PDR5 Transcription in Saccharomyces cerevisiae

“…As analyzed by the CHIP technique using Myc antibody, the recruitment signals of Pdr1 and Pdr1-3 to the PDR12 promoter, which is not subject to regulation by PDR1 (47,48), were at least 10-fold lower than those to the PDR5 UAS sequences. These data indicate that Pdr1 and Pdr1-3 activators bind the PDR5 promoter in a specific manner.…”

Novel stress responses facilitate Saccharomyces cerevisiae growth in the presence of the monocarboxylate preservatives

“…Resistances are induced to Acetic, but not propionic, sorbic or benzoic acids [19] Propionic, sorbic, benzoic acids, but not acetic acid [1,7] Key induced signalling pathway and activity HOG pathway signalling, leading to Hog1p MAP kinase activation [19] No evidence for a signalling pathway involvement; acid anion may act directly on the War1p transcription factor [13] Key action/target of the induced activity needed for the acquisition of resistance Phosphorylation of Fps1p, leading to Fps1p endocytosis [20] PDR12 gene induction, leading to an elevated plasma membrane level and activity of the Pdr12p ABC transporter [23,28] Probable related stress response Hog1p-directed downregulation of metalloid entry through the Fps1p channel [40] War1p activation in media containing leucine, methionine or phenylalanine as sole nitrogen source [9] Normal physiological function of the major target of the response Fps1p is the major glycerol channel of the plasma membrane, important for osmoadaptation [10,22,38] Pdr12p is also involved in export of the potentially toxic aromatic and branched-chain organic acids produced during amino acid catabolism [9] (2), a MAP kinase constitutively bound to, and that directly phosphorylates, Fps1p (3). This phosphorylation provides the signal for Fps1p endocytosis and degradation, eliminating this source of the acetic acid entry to the cell.…”

“…[29] When S. cerevisiae is subjected to sorbic acid stress, War1p-directed induction of Pdr12p can be so strong that this ABC transporter rapidly becomes one of the most abundant proteins of the yeast plasma membrane. [23,24] In vivo, the activity of Pdr12p can be readily monitored as the energy-dependent extrusion from the cell of benzoate [23] or fluorescein. [11] It appears, therefore, that Pdr12p confers resistance by catalysing the active extrusion of the preservative anion (against its concentration gradient) from the cell, thereby lowering intracellular levels of the preservative (Figure 2b).…”

“…This is an ABC transporter that provides resistance to those carboxylate compounds that can, to a reasonable extent, partition into both lipid and aqueous phases. [7,11,13,23,28] It may therefore initially bind acid anions that have become incorporated within the inner leaflet of the plasma membrane, anions orientated with their polar carboxylate groups exposed on the cytosolic surface of this membrane, then act by transporting these to the opposite (periplasmic) side of the membrane (i.e. act as a 'flippase'; Figure 2b).…”

Yeast ABC transporters – A tale of sex, stress, drugs and aging

“…Notably, Pdr12p does not transport hydrophobic drugs, but confers resistance to weak organic acids. Pdr12p, the closest homologue of Snq2p, mediates energy-dependent extrusion of water-soluble carboxylate anions, such as those used for food preservation, including benzoate, sorbate and propionate [17].…”