Isolation and analysis of differentially expressed genes in Penicillium glabrum subjected to thermal stress

1 Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, Université Européenne de Bretagne, Ecole Supérieure de Microbiologie et Sécurité Alimentaire de Brest, Technopôle Brest-Iroise, 28280 Plouzané, France 2 Evolution et Génétique des Populations Marines, UMR CNRS 7144, Université Pierre et Marie Curie, Station Biologique de Roscoff, Place Georges Teissier, 29682 Roscoff Cedex, France 3 Plate-forme Transcriptomique Ouest-Génopôle, Institut du Thorax INSERM U533, 1 Rue Gaston Veil, BP 53508, 44035 Nantes, Cedex 1, France Correspondence V. Vasseur valerie.vasseur{at}univ-brest.fr Penicillium glabrum is a filamentous fungus frequently involved in food contamination. Numerous environmental factors (temperature, humidity, atmospheric composition, etc.) or food characteristics (water activity, pH, preservatives, etc.) could represent potential sources of stress for micro-organisms. These factors can directly affect the physiology of these spoilage micro-organisms: growth, conidiation, synthesis of secondary metabolites, etc. This study investigated the transcriptional response to temperature in P. glabrum , since this factor is one of the most important for fungal growth. Gene expression was first analysed by using suppression subtractive hybridization to generate two libraries containing 445 different up- and downregulated expressed sequence tags (ESTs). Expression of these ESTs was then assessed for different thermal stress conditions, with cDNA microarrays, resulting in the identification of 35 and 49 significantly up- and downregulated ESTs, respectively. These ESTs encode heat-shock proteins, ribosomal proteins, superoxide dismutase, trehalose-6-phosphate synthase and a large variety of identified or unknown proteins. Some of these may be molecular markers for thermal stress response in P. glabrum . To our knowledge, this work represents the first study of the transcriptional response of a food spoilage filamentous fungus under thermal stress conditions. Abbreviations: aRNA, amplified RNA; EST, expressed sequence tag; HSP, heat-shock protein; qRT-PCR, real-time quantitative reverse-transcription PCR; SSH, suppression subtractive hybridization Two supplementary tables with details of the up- and downregulated ESTs are available with the online version of this paper.