Induction of Sexual Reproduction and Genetic Diversity in the Cheese Fungus Penicillium Roqueforti
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Induction of sexual reproduction and genetic diversity in the cheese fungus Penicillium roqueforti Jeanne Ropars, Manuela Lopez-Villavicencio, Joelle Dupont, Alodie Snirc, Guillaume Gillot, Monika Coton, Jean-Luc Jany, Emmanuel Coton, Tatiana Giraud To cite this version: Jeanne Ropars, Manuela Lopez-Villavicencio, Joelle Dupont, Alodie Snirc, Guillaume Gillot, et al.. Induction of sexual reproduction and genetic diversity in the cheese fungus Penicillium roqueforti. Evolutionary Applications, Blackwell, 2014, 10.1111/eva.12140. hal-01302704 HAL Id: hal-01302704 https://hal.archives-ouvertes.fr/hal-01302704 Submitted on 14 Apr 2016 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. 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Evolutionary Applications Evolutionary Applications ISSN 1752-4571 ORIGINAL ARTICLE Induction of sexual reproduction and genetic diversity in the cheese fungus Penicillium roqueforti Jeanne Ropars,1,2 Manuela Lopez-Villavicencio, 3,*Joelle€ Dupont,3 Alodie Snirc,1,2 Guillaume Gillot,4 Monika Coton,4 Jean-Luc Jany,4 Emmanuel Coton4 and Tatiana Giraud1,2,* 1 Ecologie, Systematique et Evolution, Universite Paris-Sud, Orsay Cedex, France 2 CNRS Orsay Cedex, France 3 Origine, Structure, Evolution de la Biodiversite, UMR 7205 CNRS-MNHN, Museum National d’Histoire Naturelle, Paris Cedex 05, France 4 Universite de Brest, EA 3882, Laboratoire Universitaire de Biodiversite et d’Ecologie Microbienne, ESIAB, Technopole^ Brest-Iroise, Plouzane, France Keywords Abstract Aspergillus, domestication, HGT, population structure, sex, wild strains, yeast The emblematic fungus Penicillium roqueforti is used throughout the world as a starter culture in the production of blue-veined cheeses. Like other industrial fila- Correspondence mentous fungi, P. roqueforti was thought to lack a sexual cycle. However, an abil- Tatiana Giraud and Manuela Lopez- ity to induce recombination is of great economic and fundamental importance, Villavicencio, Ecologie, Systematique et as it would make it possible to transform and improve industrial strains, promot- Evolution, Universite Paris-Sud, Batiment 360, ing the creation of novel phenotypes and eliminating the deleterious mutations 91405 Orsay Cedex, France. Tel.: +33 1 69 15 56 69; that accumulate during clonal propagation. We report here, for the first time, the fax: +33 1 69 15 46 97; induction of the sexual structures of P. roqueforti — ascogonia, cleistothecia and e-mails: [email protected] and ascospores. The progeny of the sexual cycle displayed clear evidence of recombi- [email protected] nation. We also used the recently published genome sequence for this species to develop microsatellite markers for investigating the footprints of recombination *These authors cosupervised the work. and population structure in a large collection of isolates from around the world and from different environments. Indeed, P. roqueforti also occurs in silage, wood Received: 20 September 2013 Accepted: 22 November 2013 and human-related environments other than cheese. We found tremendous genetic diversity within P. roqueforti, even within cheese strains and identified six doi:10.1111/eva.12140 highly differentiated clusters that probably predate the use of this species for cheese production. Screening for phenotypic and metabolic differences between these populations could guide future development strategies. Penicillium roqueforti is used in the production of the Introduction French cheese Roquefort and in many other blue-veined Cheese is an important foodstuff introduced into the cheeses around the world, including Italian gorgonzola, human diet in the early Neolithic Era (Beresford et al. Danablue in Denmark, Stilton in United Kingdom and 2001; Salque et al. 2013). Cheese-making increases the Cabrales in Spain. This species is therefore of great eco- quality and duration of milk conservation and the nomic importance. In France alone, the total production of digestibility of lactose (Bennett and Johnston 2004). Roquefort and other blue cheeses reached almost 57 000 Two categories of microorganisms are required for tonnes in 2011 (Martin-Houssart 2012). Indeed, Roquefort cheese-making: primary and secondary flora (Salque cheese is one of the most emblematic cheeses in France, et al. 2013). The primary flora consists of lactic acid produced and exported in large amounts, and it was the bacteria, which have been studied in detail (Mounier first cheese to obtain the ‘Appellation d’Origine Controlee’ et al. 2008; Irlinger and Mounier 2009; Douglas and (AOC) label, which guarantees the origin of traditional Klaenhammer 2010). The secondary flora develops after French products. By contrast to many other industrial the environment has been modified by the primary flora species, such as P. camemberti, wild strains of P. roqueforti and consists of a mixture of bacteria, yeasts and moulds can be found, allowing comparisons between industrial playing an important role in the texture and flavour of and wild strains for understanding the domestication cheeses. process and history. In addition to its presence in dairy © 2014 The Authors. Evolutionary Applications published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative 1 Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Cheesy sex Ropars et al. environments, P. roqueforti is a common spoilage agent in structure in a large collection of 114 isolates from different refrigerated stored foods, meat, wheat products and silage, environments and locations (Table S1). and it is even found in forest soil and wood (Pitt and Hocking 2009). Materials and methods Penicillium roqueforti, like other industrial filamentous fungi and an estimated one-fifth of fungal species, was Fungal isolates thought to lack a sexual cycle. However, evidence for the We used 114 strains of P. roqueforti described in a previous occurrence of sexual reproduction has been obtained for study (Ropars et al. 2012) (Table S1). All these strains are many of the supposed ‘asexual’ species (Burt et al. 1996; kept in the collection of the Natural History Museum in Pringle et al. 2005; Rydholm et al. 2006), and indirect evi- Paris or the LUBEM collection. The fungal strains were of dence of sexual reproduction has recently been reported for industrial origin or obtained from silage and natural habi- P. roqueforti (Ropars et al. 2012). Mating type genes (MAT tats. Single-spore isolation was systematically carried out genes), which are involved in gamete recognition and by a dilution method to guarantee that colonies originated mating in fungi, and other genes involved in meiosis, have from a single genotype. been detected in the P. roqueforti genome and appear to be subject to strong purifying selection, suggesting that they DNA extraction are still used and functional. Haploid strains of P. roquefor- ti carry a single allele of the MAT gene in their genome, as Genomic DNA was extracted from fresh mycelium of the all heterothallic fungi, meaning that fusion is possible only isolates listed in Table S1 grown for 3–5 days on malt agar. between gametes with opposing MAT alleles. Population The Qiagen DNeasy Plant Mini Kit (Qiagen, Ltd. Crawley, analyses with polymorphic markers have revealed foot- UK) was used for DNA extraction and purification. We prints of recombination and both MAT alleles have been used the 5′ end of the b-tubulin gene (oligonucleotide detected. Other indirect evidence for the occurrence of sex primer set Bt2a/Bt2b; Glass and Donaldson 1995) to type in P. roqueforti includes the detection of RIP (repeat- strains, to ensure that they belonged to the P. roqueforti induced point mutation) footprints (Ropars et al. 2012), a species (Samson et al. 2004). phenomenon in which repeated sequences are mutated and which occurs in fungi exclusively during the dikaryotic Induction of sex phase between syngamy and meiosis. However, sexual structures have never been observed in Eight P. roqueforti isolates were crossed in all possible pair- P. roqueforti, in either natural or controlled conditions. wise MAT1-1 (four strains) and MAT1-2 (four strains) Industrial strains are maintained by ferment producers and combinations, in duplicate, following the protocol recently are replicated clonally. As for other industrial species, published for P. chrysogenum (Bohm€ et al. 2012). Two dif- efforts to identify novel traits have thus been based purely ferent media culture were used, oatmeal agar (Bohm€ et al. on random mutagenesis and screening (Poggeler€ 2001). 2012) and goat-cheese agar media (Decker and Nielsen The possibility of inducing a sexual cycle would be of con- 2005), both supplemented with biotin (6.4 lg/L) after auto- siderable interest for industrial purposes, as it would facili- claving (Bohm€ et al. 2012). Petri dishes were sealed with tate the generation, by recombination, and selection of Parafilm and incubated at 15 or 25°C in the dark. For each interesting new traits, in terms of colour, growth rate and isolate, spore suspensions