In vitro and in situ unraveling truffle sexual reproduction using Ascobolus immersus as a test tube model

PI : Claude Murat (UMR 1136 Tree/Microorganism Interactions — IAM))

Co-applicants :

International
Francesco Paolocci, CNR – Institute of Biosciences and Bioresources (IBBR-DNR), Perugia, Italie

IDEX Paris-Saclay
Fabienne Malagnac, I2BC, UMR 9198 CEA, CNRS, Université Paris Sud

Truffle sector
Dominique Barry, ALCINA
Michel Tournayre, Fédération Française des Trufficulteurs (FFT)

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Context — Truffles are ectomycorrhizal fungi naturally found in France and Lorraine. Several truffle species produce fruiting bodies with appreciated organoleptic qualities. Ascobolus immersus is a fungal species, used as a model organism, belonging to Pezizomycete, an early diverging lineage of Pezizomycotina. While the genomic resources in this class have increased, genetic tools are still lacking for most of the species, such as truffles. As requested by truffle industry, a better understanding of the sexual reproduction of truffles is critical to improving their production. Since A. immersus can be genetically modified and can complete its sexual cycle under laboratory conditions, we believe that it could be a model system to address fundamental questions concerning Pezizomycetes, such as recognition between strains of opposite mating types within and between Tuber species.

Objectives — The principal objectives of the AscoTube project are 1) to use A. immersus as a model species to address fundamental questions on truffles, and 2) to gain a better understanding of truffle sexual reproduction in situ.

Approach — The AscoTube project involves several active partners: French research teams (IAM, I2BC), Italian academic research teams (CNR-IBBR), truffle industry associations (FFT) and one privately owned company (ALCINA). A. immersus will be used as model species to study the genetic mechanisms underlying recognition between strains of opposite mating types in Tuber spp. This in vitro approach will be complemented with in situ experiments aimed at detecting and following the dynamics of both mating types.

Expected results and impacts —We anticipate that the proposed approach will provide important knowledge on truffle sexual reproduction and will confirm the function of bioinformatically annotated gene models. Expected main outcomes will be new tools for basic research, a deeper understanding of truffle sexual reproduction and new policy recommendations if outcrossing between different truffle species can be demonstrated (e.g. between black European and Chinese truffle).