APPLIED GENETICS AND MOLECULAR BIOTECHNOLOGY Expression of phenol oxidase and heat-shock genes during the development of Agaricus bisporus fruiting bodies, healthy and infected by Lecanicillium fungicola Michèle L. Largeteau & Camille Latapy & Nathalie Minvielle & Catherine Regnault-Roger & Jean-Michel Savoie Received: 29 April 2009 / Revised: 3 August 2009 / Accepted: 4 August 2009 / Published online: 27 August 2009 # Springer-Verlag 2009 Abstract The fungal pathogen Lecanicillium fungicola (formerly Verticillium fungicola) is responsible for severe losses worldwide in the mushroom (Agaricus bisporus) industry. Infected crops are characterised by masses of undifferentiated tissue (bubbles) growing in place of spor- ophores. The expression of three laccase genes (lcc1, lcc2 and lcc3), two tyrosinase genes (AbPPO1 and AbPPO2) and the hspA gene encoding a heat-shock protein known to be potentially associated with host–pathogen interaction was investigated in mycelial aggregates and during the develop- ment of healthy sporophores and bubbles of a susceptible cultivar. The lcc3, AbPPO2 and hspA genes were each expressed at different levels at the different stages of sporophore morphogenesis, whilst they showed a stable expression throughout bubble development. The transcript levels were similar in bubbles and at the first developmental stage of healthy fruiting bodies, both showing no tissue differentiation. These observations suggest that lcc3, AbPPO2 and hspA are associated with A. bisporus morpho- genesis. Comparing the expression of the hspA gene in three susceptible and three tolerant strains showed that the latter displayed a higher level of transcript in the primordium, which is the stage receptive to the pathogen. The six strains exhibited a comparable expression in the vegetative myce- lium, non-receptive to L. fungicola. Keywords Fungal pathogen . Mushroom . Gene expression . HSP70 . Laccase . Tyrosinase Introduction Dry bubble disease is the most common and serious fungal disease of Agaricus bisporus. The causal agent, commonly known as Verticillium fungicola (Preuss) Hassebrauk, was recently renamed as Lecanicillium fungicola (Preuss) Zare and Gams (Zare and Gams 2008). L. fungicola infection is manifested in three types of symptoms designed spotty cap, stipe blowout and bubble. Although the three types of symptoms coexist in infected cultures, the pathology is named dry bubble disease. Candidate genes expressed during lesion (spots) development on fully developed sporophores were identified (Amey et al. 2003; Thomas et al. 2007). Cap-spotting mainly affects the surface of the fruiting body and is considered the least severe symptom of the disease. The most severe symptom is bubble, a spherical mass with little or no tissue differentiation, which consists of mycelia of L. fungicola and A. bisporus growing together. The regulation of A. bisporus morphogenesis is beginning to be understood (Ospina-Giraldo et al. 2000; Sreenivasaprasad et al. 2000, 2004; Eastwood et al. 2008) but the biochemical and molecular bases of the processes involved remain largely unknown. Several works showed the putative involvement of phenol oxidases and heat-shock proteins in interspecific hyphal interaction and morphogen- esis. Changes in activity and isozymes of laccase were observed in various interactions between basidiomycetes and ascomycetes (Score et al. 1997; Savoie et al. 1998; Savoie and Mata 1999; Velasquez-Cedeno et al. 2004; Xiao et al. 2004). Laccase isozymes were detected in bubbles, M. L. Largeteau (*) : C. Latapy : N. Minvielle : J.-M. Savoie UR1264, Mycologie et Sécurité des Aliments, INRA, BP81, 33883 Villenave d’Ornon, France e-mail: largeteau@bordeaux.inra.fr C. Regnault-Roger UFR Sciences et Techniques, UPPA (Université Pau et Pays de l’Adour), 64012 Pau Université, France Appl Microbiol Biotechnol (2010) 85:1499–1507 DOI 10.1007/s00253-009-2186-2