Posts Tagged ‘Tuber’

Unearthing the truffle genome

February 5th, 2011

np‘The ‘black diamond’, the ‘mysterious product of the earth’, the ‘ultimate fungus’ and ‘la grande mystique’ are some of the common names describing the delectable Périgord black truffle (Tuber melanosporum Vitt.). The culture, harvesting and marketing of this highly prized ectomycorrhizal fungus is a world that retains some of the secrets and intrigue of the past. Truffle cultivation is notoriously difficult, in part because of its cryptic life cycle as an underground symbiont, in which the fungus trades nutrients with oak-tree roots. By the end of the 1960s, there had been some success in devising new methods for producing truffle-infected seedlings under controlled conditions in glasshouses by inoculating plants with truffle cultures and spores. After successful plantation in orchards, reliable information on truffle yields and production is very difficult to obtain as a result of under-reporting of harvests, under-the-table marketing practices and a lack of administration records. It appears, however, that the production of truffles, as with other mushrooms, is erratic from year to year (depending on the weather conditions) and tends to decline as a result of global climate change. Decreasing supply and rising market prices have provided a strong incentive for research on truffle cultivation.’ (from my edito)

The February issue of New Phytologist (189: 3) includes a Special Feature dedicated to the Perigord Truffle genome with 7 papers discussing the transcriptome, the repertoire of transcriptional factors, the carbohydrate metabolism, the aroma biosynthesis and the molecular ecology  of sex of this ultimate fungus. Another raft of companion papers have been published in Fungal, Genetics & Biology.

To date, genomes of two mutualistic fungal symbionts, the basidiomycete L. bicolor and the ascomycete Tuber melanosporum, have been sequenced.  Based on their symbiosis-induced gene networks, evolution of the ectomycorrhizal lifestyle appears to be quite divergent (Plett & Martin, 2011).  To better understand the differences between symbiotic lineages and types of symbiosis, our JGI project is aiming to sequence 25 mycorrhizal fungi from different orders.  As of today, genomic DNA from Amanita muscaria, Cenococcum geophilum, Hebeloma cylindrosporum, Laccaria amethystina, Oidiodendron maius, Piloderma croceum, Paxillus involutus, Pisolithus microcarpus and P. tinctorius is currently being sequenced using next generation sequencing platforms. Sequencing of Boletus edulis, Cantharellus cibarius, Coltricia cinnamomea, Cortinarius glaucopus, Gymnomyces xanthosporus, Lactarius quietus, Meliniomyces bicolor, Paxillus rubicundulus, Ramaria formosa, Rhizoscyphus ericeae, Scleroderma citrinum, Suillus luteus, Sebacina vermifera, Tomentella sublilacina, Tricholoma matsutake, Tulasnella calospora and Terfezia boudieri will follow in 2011.

Blurred Boundaries

December 4th, 2010

PoplarLaccariaECMOur review paper on the genomes of ectomycorrhizal fungi is available online at the Trends in Genetics site.

Plett JM & Martin F. 2010. Blurred boundaries: lifestyle lessons from ectomycorrhizal fungal genomes. Trends in Genetics. doi:10.1016/j.tig.2010.10.005

Abstract. “Soils contain a multitude of fungi with vastly divergent lifestyles ranging from saprotrophic to mutualistic and pathogenic. The recent release of many fungal genomes has led to comparative studies that consider the extent to which these lifestyles are encoded in the genome. The genomes of the symbiotic fungi Laccaria bicolor and Tuber melanosporum are proving especially useful in characterizing the genetic foundation of mutualistic symbiosis. New insights gleaned from these genomes, as compared to their saprotrophic and pathogenic cousins, have helped to redefine and shape our understanding of the nature of the symbiotic lifestyle. Here we detail the current state of research into this complex relationship and discuss avenues for future exploration.”

Photo: section of Populus/Laccaria ectomycorrhizal root – JM Plett © INRA.

Sex Wars of the Truffle Grounds

October 28th, 2010

Tuber_melanosporumLa Truffe … encore et encore !!!

It’s been busy press days for our New Phytologist article on the distribution of mating-type (MAT) genes in a truffle ground! The news coverage  grows by the minute … just amazing how this ‘ultimate’ mushroom is causing a stir. It ‘s nice that this work is reaching a much broader audience (and for not much effort on our part!). Of course having the key words ‘truffle’ and ‘sex wars’ in the headline helped.

Here is the Press Release: “They are one of the most highly prized delicacies in the culinary world, but now scientists have discovered that black truffles are locked in a gender war for reproduction. The research, published in New Phytologist as the truffle season begins, represents a breakthrough in the understanding of truffle cultivation and distribution.

The teams, led by Dr Francesco Paolocci and Dr Andrea Rubini from the CNR Plant Genetics Institute in Perugia and by Dr Francis Martin from INRA in Nancy, carried out their research on the reproduction strategy of the highly prized black truffle, Tuber melanosporum, which is grown across southern Europe. During the truffle season, between late autumn and winter, fruiting truffles can grow up to 7cm in diameter, weighing up to 100g with a value often measured in hundreds of Euros.

‘Fruiting’ is the crucial part of the truffle life cycle, occurring when the fungi interacts with and colonises host plants, usually at the roots. However, the process which causes this transition from vegetative to reproductive state remains unknown.

“It is commonly believed that truffles, like other fungi, are homothallic, meaning that they reproduce themselves,” said Paolocci. “Because fungi that reproduce this way do not need a sexual partner it was believed that truffle cultivation relied only on the environment and nutrition, now we know that is wrong.”

Taking advantage of the information provided by the T. melanosporum genome sequencing project led by Martin and from molecular analyses carried out by the Italian team, research now proves that truffles do outcross, meaning they are a two gender species, with sexual reproduction occurring between strains of opposite mating types.

The team studied samples of wild black truffle strains on plants from a natural truffle ground near Spoleto in central Italy. The study revealed that black truffle strains of opposite gender were not evenly distributed beneath potentially productive soil patches.

The team then studied the dynamics of truffle strains on host plants, artificially inoculated with truffle spores and grown in a greenhouse, which showed that a competition occurs between strains to colonise the host plant roots even under controlled conditions.

The truffle fruiting season traditionally begins in late autumn but sexual reproduction is believed to occur in spring. The Italian team demonstrated that during the latter season strain of opposite gender are present in the soil samples next to colonised host plants and that the host plant colonising strain acts as maternal partner in the reproductive process.

These findings represent a breakthrough in the understanding of truffle reproduction tactics as well as the dynamics of black truffle strains in both open-field conditions and on host plants produced to boost truffle production.

“These results are of considerable practical use for optimising and increasing production in truffle fields,” concluded Paolocci. “It is of paramount interest to artificial truffle plantations to encourage a balance of strains of both mating types. Future investigations will allow us to determine whether the distribution of mating types is a factor that truly limits truffle fruiting body production.”

Andrea Rubini, Beatrice Belfiori, Claudia Riccioni, Sergio Arcioni, Francis Martin, Francesco Paolocci. Tuber melanosporum: mating type distribution in a natural plantation and dynamics of strains of different mating types on the roots of nursery-inoculated host plants. New Phytologist, 2010; DOI: 10.1111/j.1469-8137.2010.03493.x

Martin et al. (2010) Perigord black truffle genome uncovers evolutionary origins and mechanisms of symbiosis. Nature 464, 1033-1038.

Photo: The Black Truffle of Perigord (Tuber melanosporum) © C Murat -INRA.

Chinese and Perigord Black Truffles

April 3rd, 2010

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A TV crew and a photograph from Reuters visited the lab on Thursday. We had a lot of fun in mimicking the DNA typing of the Chinese and Perigord black truffles . As we claimed: “DNA fingerprinting will help identify the regional origin of harvested truffles and set up the means to certify these products and detect any frauds”.

Photo: Claude Murat handling a T. indicum and  T. melanosporum in his right and left hand, respectively. © Reuters/INRA.