oa Editorial [Hot Topic: Fungal Model Systems to Understand the Mechanisms Unravelling the Oxidative Stress Response (Guest Editor: Maria Angeles de la Torre Ruiz)]

Oxidative stress occurs as a consequence of aerobic life. ROS (Reactive oxygen species) cause important cellular damage to prokaryotic and eukaryotic cells. Oxidation of different molecules in eukaryotic cells is the cause of many human diseases; examples of them include atherosclerosis, Parkinson's and Alzheimer's diseases, mental disorders and others. During decades, researchers have been developing new strategies to counteract the pernicious effects of the oxidative stress. One of the main important cues of these studies is to know and to characterise at the molecular level all the cellular processes involved in cell sensing, signalling, transduction and the adaptive responses to oxidative stress. The characterisation of early and late responses and the adaptive mechanism to oxidants, are of major interest in order to develop new antioxidants and drugs to counteract the noxious effects of oxidative stress. Moreover, since oxidative stress is one of the main causes of aging and cell death, knowledge of those processes circumventing aging is tour aim in order to extend human life. In this special issue, an overview of the current knowledge of different aspects of oxidative stress it is shown, developed upon the study of different fungal systems. Fungi are microorganisms. As unicellular systems, they are relatively easy to manipulate and modify genetically. Fungi are eukaryotic cells. Consequently they are suitable model systems since they present a high degree of similarity with human cells. In addition, yeast data bases are the most extended, containing the most complete genetic information to date. The model systems reviewed in the current issue include Saccharomyces cerevisiae, Schizosaccharomyces pombe, Candida albicans and Aspergillus nidulans. S. cerevisiae is a very well known model system. Studies based in this system have contributed to extend the knowledge of the molecular mechanisms circumventing oxidative stress by using genomic and proteomic approaches. It is a very suitable model to study biochemical and molecular mechanisms related to antioxidant enzymes, glutaredoxins and thioredoxins, among others. Moreover, in the past decades many advances have been achieved in the study of the processes of sensing and transducing the oxidative signal to the nucleus, along with various mechanisms of cellular responses and adaptation to oxidative stress. These mechanisms include those related to the actin cytoskeleton remodelling and in general to morphogenetic processes. In parallel, and with similar relevance, a huge number of studies have been developed with Schizosaccharomyces pombe, another very well known yeast system. In fact, both yeast models, S. cerevisiae and S. pombe, have largely contributed to increase the knowledge of these responses, as detailed in this issue. Candida albincans is a diploid unicellular eukaryotic system whose study complements the knowledge obtained from the haploids systems S. cerevisiae and S. pombe. Of special relevance in microbiology is the study of the oxidative stress in the context of Candida albicans virulence, since this yeast can be an opportunistic pathogen. In this respect, the study of those mechanisms developed by Candida albicans in the oxidative stress response, can favour the identification of different specific cellular targets in order to design new drugs that block the proliferation of possible fungal pathogens. Aspergillus nidulans is a nascent cellular model that is importantly contributing to increase the knowledge of the oxidative stress responses and in general of the signal transduction mechanisms associated whit it. Again, A. nidulans, as in the case of C. albincas, can offer more information related to microbial virulence as for example the development of new antifungal drugs.