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Open Access Highly Accessed Research article

A genomic approach highlights common and diverse effects and determinants of susceptibility on the yeast Saccharomyces cerevisiae exposed to distinct antimicrobial peptides

Belén López-García12, Mónica Gandía1, Alberto Muñoz13, Lourdes Carmona1 and Jose F Marcos1*

Author Affiliations

1 Departamento de Ciencia de los Alimentos, Instituto de Agroquímica y Tecnología de Alimentos (IATA), CSIC, Apartado de Correos 73, Burjassot, 46100 Valencia, Spain

2 Departamento de Genética Molecular de Plantas, Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB, Barcelona, Spain

3 Fungal Cell Biology Group, Institute of Cell Biology (ICB), University of Edinburgh, Rutherford Building, Edinburgh EH9 3JH, UK

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BMC Microbiology 2010, 10:289  doi:10.1186/1471-2180-10-289

Published: 15 November 2010

Abstract

Background

The mechanism of action of antimicrobial peptides (AMP) was initially correlated with peptide membrane permeation properties. However, recent evidences indicate that action of a number of AMP is more complex and involves specific interactions at cell envelopes or with intracellular targets. In this study, a genomic approach was undertaken on the model yeast Saccharomyces cerevisiae to characterize the antifungal effect of two unrelated AMP.

Results

Two differentiated peptides were used: the synthetic cell-penetrating PAF26 and the natural cytolytic melittin. Transcriptomic analyses demonstrated distinctive gene expression changes for each peptide. Quantitative RT-PCR confirmed differential expression of selected genes. Gene Ontology (GO) annotation of differential gene lists showed that the unique significant terms shared by treatment with both peptides were related to the cell wall (CW). Assays with mutants lacking CW-related genes including those of MAPK signaling pathways revealed genes having influence on sensitivity to peptides. Fluorescence microscopy and flow cytometry demonstrated PAF26 interaction with cells and internalization that correlated with cell killing in sensitive CW-defective mutants such as Δecm33 or Δssd1. GO annotation also showed differential responses between peptides, which included ribosomal biogenesis, ARG genes from the metabolism of amino groups (specifically induced by PAF26), or the reaction to unfolded protein stress. Susceptibility of deletion mutants confirmed the involvement of these processes. Specifically, mutants lacking ARG genes from the metabolism of arginine pathway were markedly more resistant to PAF26 and had a functional CW. In the deletant in the arginosuccinate synthetase (ARG1) gene, PAF26 interaction occurred normally, thus uncoupling peptide interaction from cell killing. The previously described involvement of the glycosphingolipid gene IPT1 was extended to the peptides studied here.

Conclusions

Reinforcement of CW is a general response common after exposure to distinct AMP, and likely contributes to shield cells from peptide interaction. However, a weakened CW is not necessarily indicative of a higher sensitivity to AMP. Additional processes modulate susceptibility to specific peptides, exemplified in the involvement of the metabolism of amino groups in the case of PAF26. The relevance of the response to unfolded protein stress or the sphingolipid biosynthesis, previously reported for other unrelated AMP, was also independently confirmed.