Desert truffle genomes reveal their reproductive modes and new insights into plant-fungal interaction and ectendomycorrhizal lifestyle

Desert truffles are edible hypogeous fungi forming ectendomycorrhizal symbiosis withplants of Cistaceae family. Knowledge about the reproductive modes of these fungi and themolecular mechanisms driving the ectendomycorrhizal interaction is lacking. Genomes of the highly appreciated edible desert truffles Terfezia claveryi Chatin andTirmania nivea Trappe have been sequenced and compared with other Pezizomycetes. Transcriptomesof T. claveryi 9 Helianthemum almeriense mycorrhiza from well-watered anddrought-stressed plants, when intracellular colonizations is promoted, were investigated. We have identified the fungal genes related to sexual reproduction in desert truffles anddesert-truffles-specific genomic and secretomic features with respect to other Pezizomycetes,such as the expansion of a large set of gene families with unknown Pfam domains and a numberof species or desert-truffle-specific small secreted proteins differentially regulated in symbiosis.A core set of plant genes, including carbohydrate, lipid-metabolism, and defencerelatedgenes, differentially expressed in mycorrhiza under both conditions was found. Our results highlight the singularities of desert truffles with respect to other mycorrhizalfungi while providing a first glimpse on plant and fungal determinants involved in ecto to endosymbiotic switch that occurs in desert truffle under dry conditions.