Rooting around in the truffle genome

The genomes of four truffle species are reported in a paper published online this week in Nature Ecology & Evolution. These findings reveal the genetic underpinnings of one of the world’s most aromatic and expensive foods.

Truffles are the spore-filled, fruiting bodies of fungi that grow on plant roots. Truffle-forming species have evolved independently more than a hundred times, appearing in nearly every major group of fleshy fungi; however, fundamental questions about the evolution of the truffle lifestyle remain.

Francis Martin and colleagues sequenced the genomes of the prized Piedmont white truffle and the Burgundy, desert and pig truffles. The authors compared these genomes with the Périgord black truffle and non-truffle-forming fungi and uncover unexpected genetic similarities among the truffle species, despite their separate evolutionary paths since their divergence over hundreds of millions of years. For example, they find shared genes relating to truffles’ symbiosis with plants and their ability to derive nutrients from the soil. They also find that truffles have a limited set of the genes that allow other fungi to specialize in breaking down the cell walls of the plants on which they live. Instead, truffles have a wider repertoire of genes that produce smelly volatile organic compounds, generating the pungent aroma that attracts animals (such as pigs and truffle dogs) to disperse the truffle’s spores.

This study is part of the 1000 Fungal Genomes Project - a five-year initiative intended to fill the gaps in our understanding of one of the largest branches in the tree of life.