The SPI1 Gene, Encoding a Glycosylphosphatidylinositol-Anchored Cell Wall Protein, Plays a Prominent Role in the Development of Yeast Resistance to Lipophilic Weak-Acid Food Preservatives

Abstract

The Saccharomyces cerevisiae SPI1 gene encodes a member of the glycosylphosphatidylinositol-anchored cell wall protein family. In this work we show results indicating that SPI1 expression protects the yeast cell from damage caused by weak acids used as food preservatives. This is documented by a less extended period of adaptation to growth in their presence and by a less inhibited specific growth rate for a parental strain compared with a mutant with SPI1 deleted. Maximal protection exerted by Spi1p against equivalent concentrations of the various weak acids tested was registered for the more lipophilic acids (octanoic acid, followed by benzoic acid) and was minimal for acetic acid. Weak-acid adaptation was found to involve the rapid activation of SPI1 transcription, which is dependent on the presence of the Msn2p transcription factor. Activation of SPI1 transcription upon acetic acid stress also requires Haa1p, whereas this recently described transcription factor has a negligible role in the adaptive response to benzoic acid. The expression of SPI1 was found to play a prominent role in the development of yeast resistance to 1,3-␤-glucanase in benzoic acidstressed cells, while its involvement in acetic acid-induced resistance to the cell wall-lytic enzyme is slighter. The results are consistent with the notion that Spi1p expression upon weak-acid stress leads to cell wall remodeling, especially for the more lipophilic acids, decreasing cell wall porosity. Decreased cell wall porosity, in turn, reduces access to the plasma membrane, reducing membrane damage, intracellular acidification, and viability loss.

Genome-Wide Identification of S accharomyces cerevisiae Genes Required for Maximal Tolerance to Ethanol

“…Our results point out an important role of some genes involved in phospholipid and ergosterol biosynthesis as part of this adaptive response, consistent with previous reports indicating that there are changes at the level of plasma membrane composition in response to ethanol stress (1,6,53). Decreased cell envelope permeability to weak organic acids was found to depend on cell wall remodeling, leading to increased lyticase resistance (40,41). The importance of the cell wall composition in yeast resistance to ethanol-induced stress has been previously pointed out, based on the fact that sake yeasts, which tolerate a very high ethanol concentration (up to 20%), are more resistant to the cell wall-targeted drugs K1 toxin and zymolase (31).…”

“…Changes in membrane composition in response to ethanol-induced stress at the level of phospholipids and ergosterol composition have been described before (1,6,53). To check whether cell wall remodeling occurs during the yeast response to ethanol shock, the very simple 1,3-ß-glucanase sensitivity assay, which has been shown to be valuable in monitoring cell wall alterations (40,41), was used. Yeast cells grown in a culture medium in the absence of ethanol were seen to be more susceptible to lyticase activity than cells exposed for 3 hours to cultivation in the presence of 6% ethanol (Fig.…”

The Yak1 Protein Kinase Lies at the Center of a Regulatory Cascade Affecting Adhesive Growth and Stress Resistance inSaccharomyces cerevisiae

“…Moreover, our data demonstrate an important role of Yak1 in control- ling not only adhesion, but also acidic stress resistance. In this context, it is interesting to note that Yak1 positively regulates expression of SPI1, a gene that is highly upregulated under acetic acid stress in an Haa1-dependent manner and encodes a GPI-anchored cell wall protein that confers acidic stress resistance (Simoes et al 2006). Thus, Yak1 might contribute to acidic stress resistance by ensuring the Haa1-mediated expression of Spi1 to protect the cell by, e.g., decreasing the porosity of the cell wall.…”

Activation of Two Different Resistance Mechanisms in Saccharomyces cerevisiae upon Exposure to Octanoic and Decanoic Acids

“…This gene affects the lipid composition of the plasma membrane, limiting the passive uptake of the drug across the membrane (48). Curiously, the PDR16 homologous gene PDR17 has no effect on octanoic acid resistance, nor do other genes described to be involved in cell response to weak organic acids, such as SPI1 (38) or HAA1 (13).…”