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

Abstract : Penicillium glabrum is a filamentous fungus frequently involved in food contamination. Numerous environmental factors (temperature, humidity, atmosphere composition, etc.) or food characteristics (water activity, pH, preservatives, etc.) could represent potential sources of stress for micro-organisms. These factors can directly affect physiology of these spoilage micro-organisms: growth, conidiation, synthesis of secondary metabolites, etc. This study investigates 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 down-regulated Expressed Sequenced 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 down-regulated 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 them may be potential 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.