Mitochondrial proteomics of the acetic acid - induced programmed cell death response in a highly tolerant Zygosaccharomyces bailii - derived hybrid strain.

Joana Guerreiro,Belem Sampaio-Marques,Paula Ludovico,Ana Coelho,Cecilia Leao,Isabel Sa-Correia,Renata Soares

doi:10.15698/mic2016.02.477

Abstract

Very high concentrations of acetic acid at low pH induce programmed cell death (PCD) in both the experimental model Saccharomyces cerevisiae and in Zygosaccharomyces bailii, the latter being considered the most problematic acidic food spoilage yeast due to its remarkable intrinsic resistance to this food preservative. However, while the mechanisms underlying S. cerevisiae PCD induced by acetic acid have been previously examined, the corresponding molecular players remain largely unknown in Z. bailii. Also, the reason why acetic acid concentrations known to be necrotic for S. cerevisiae induce PCD with an apoptotic phenotype in Z. bailii remains to be elucidated. In this study, a 2-DE-based expression mitochondrial proteomic analysis was explored to obtain new insights into the mechanisms involved in PCD in the Z. bailii derived hybrid strain ISA1307. This allowed the quantitative assessment of expression of protein species derived from each of the parental strains, with special emphasis on the processes taking place in the mitochondria known to play a key role in acetic acid - induced PCD. A marked decrease in the content of proteins involved in mitochondrial metabolism, in particular, in respiratory metabolism (Cor1, Rip1, Lpd1, Lat1 and Pdb1), with a concomitant increase in the abundance of proteins involved in fermentation (Pdc1, Ald4, Dld3) was registered. Other differentially expressed identified proteins also suggest the involvement of the oxidative stress response, protein translation, amino acid and nucleotide metabolism, among other processes, in the PCD response. Overall, the results strengthen the emerging concept of the importance of metabolic regulation of yeast PCD.

Highlights

Acetic acid is a commonly used anti-microbial additive, with a broad application in the preservation of acidic foods and beverages
Characterization of strain ISA1307 global response to an acetic acid concentration inducing programmed cell death (PCD) it has already been reported that acetic acid concentrations in the range of 320 - 800 mM induce a PCD process in Z. bailii hybrid strain ISA1307 [7], this study was started by validating the experimental conditions to be used and to confirm the occurrence of massive PCD under the specific scale-up conditions of acetic acid treatment required to isolate higher amounts of mitochondrial protein extracts suitable to carry out proteomic analysis
This was evidenced by the high number of propidium iodide (PI)negative cells, indicating that plasma membrane integrity was preserved and no extensive necrosis has occurred (Fig. 1A), and by the detection of transferase - mediated dUTP nick end labeling (TUNEL)-positive cells, indicating occurrence of DNA strand breaks typical of apoptotic phenotypes (Fig. 1A-C)

Summary

Introduction

Acetic acid is a commonly used anti-microbial additive, with a broad application in the preservation of acidic foods and beverages. Under these conditions many yeasts and moulds are able to adapt and proliferate, becoming the prevailing contaminants of foods and beverages preserved at low pH [1, 2]. Proteomics of Z. bailii acetic acid - induced PCD (PCD) in both the experimental model Saccharomyces cerevisiae [6] and in Z. bailii [7] This effect is observed at much higher concentrations of the acid for Z. bailii, in the range of 320 - 800 mM, compared to 20 - 120 mM for S. cerevisiae [6,7,8]. Depending on the acid concentration, acetic acid may induce a PCD either with an apoptotic or a necrotic phenotype [6,7,8]

Methods

Results

Conclusion