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Summary: The jasmonic acid (JA) signalling pathway plays an important role in the establishment of the ectomycorrhizal symbiosis. The Laccaria bicolor effector MiSSP7 stabilizes JA corepressor JAZ6, thereby inhibiting the activity of Populus MYC2 transcription factors. Although the role of MYC2 in orchestrating plant defences against pathogens is well established, its exact contribution to ECM symbiosis remains unclear. This information is crucial for understanding the balance between plant immunity and symbiotic relationships.Transgenic poplars overexpressing or silencing for the two paralogues of MYC2 transcription factor (MYC2s) were produced, and their ability to establish ectomycorrhiza was assessed. Transcriptomics and DNA affinity purification sequencing were performed.MYC2s overexpression led to a decrease in fungal colonization, whereas its silencing increased it. The enrichment of terpene synthase genes in the MYC2‐regulated gene set suggests a complex interplay between the host monoterpenes and fungal growth. Several root monoterpenes have been identified as inhibitors of fungal growth and ECM symbiosis.Our results highlight the significance of poplar MYC2s and terpenes in mutualistic symbiosis by controlling root fungal colonization. We identified poplar genes which direct or indirect control by MYC2 is required for ECM establishment. These findings deepen our understanding of the molecular mechanisms underlying ECM symbiosis. [ABSTRACT FROM AUTHOR]

Summary: The desert truffle Terfezia claveryi is one of the few mycorrhizal fungi currently in cultivation in semiarid and arid areas. Agroclimatic parameters seem to affect its annual yield, but there is no information on the influence of biotic factors. In this study, fungal diversity was analysed by high‐throughput sequencing of the ITS2 rDNA region from soil and root samples to compare productive and non‐productive mycorrhizal plants in a 4‐years old plantation (Murcia, Spain). The fungal metaprofile was dominated by Ascomycota phylum. Desert truffle productivity was driven by different patterns of fungal species composition in soil (species replacement) and root (species richness differences). Moreover, positive associations for ectomycorrhizal and negative for arbuscular mycorrhizal guilds were found in productive roots, and positive associations for fungal parasite‐plant pathogen guild in non‐productive ones. Soil samples were dominated by pathotroph and saprotroph trophic modes, showing positive associations for Aureobasidium pullulans and Alternaria sp. in productive areas, and positive associations for Fusarium sp. and Mortierella sp. were found in non‐productive soils. Finally, some significant OTUs were identified and associated to ascocarp producing patches, which could serve as predictive and location markers of desert truffle production. [ABSTRACT FROM AUTHOR]

Summary: Desert truffles are edible hypogeous fungi forming ectendomycorrhizal symbiosis with plants of Cistaceae family. Knowledge about the reproductive modes of these fungi and the molecular mechanisms driving the ectendomycorrhizal interaction is lacking.Genomes of the highly appreciated edible desert truffles Terfezia claveryi Chatin and Tirmania nivea Trappe have been sequenced and compared with other Pezizomycetes. Transcriptomes of T. claveryi × Helianthemum almeriense mycorrhiza from well‐watered and drought‐stressed plants, when intracellular colonizations is promoted, were investigated.We have identified the fungal genes related to sexual reproduction in desert truffles and desert‐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 number of species or desert‐truffle‐specific small secreted proteins differentially regulated in symbiosis. A core set of plant genes, including carbohydrate, lipid‐metabolism, and defence‐related genes, differentially expressed in mycorrhiza under both conditions was found.Our results highlight the singularities of desert truffles with respect to other mycorrhizal fungi while providing a first glimpse on plant and fungal determinants involved in ecto to endo symbiotic switch that occurs in desert truffle under dry conditions. [ABSTRACT FROM AUTHOR]

Predicted increases in atmospheric concentration of carbon dioxide (CO2) coupled with increased temperatures and drought are expected to strongly influence the development of most of the plant species in the world, especially in areas with high risk of desertification like the Mediterranean basin. Helianthemum almeriense is an ecologically important Mediterranean shrub with an added interest because it serves as the host for the Terfezia claveryi mycorrhizal fungus, which is a desert truffle with increasingly commercial interest. Although both plant and fungi are known to be well adapted to dry conditions, it is still uncertain how the increase in atmospheric CO2 will influence them. In this article we have addressed the physiological responses of H. almeriense × T. claveryi mycorrhizal plants to increases in atmospheric CO2 coupled with drought and high vapor pressure deficit. This work reports one of the few estimations of mesophyll conductance in a drought deciduous Mediterranean shrub and evaluates its role in photosynthesis limitation. High atmospheric CO2 concentrations help desert truffle mycorrhizal plants to cope with the adverse effects of progressive drought during Mediterranean springs by improving carbon net assimilation, intrinsic water use efficiency and dispersal of the species through increased flowering events. [ABSTRACT FROM AUTHOR]