Sex in the PAC: A hidden affair in dark septate endophytes?

<p>Abstract</p> <p>Background</p> <p>Fungi are asexually and sexually reproducing organisms that can combine the evolutionary advantages of the two reproductive modes. However, for many fungi the sexual cycle has never been observed in the field or <it>in vitro </it>and it remains unclear whether sexual reproduction is absent or cryptic. Nevertheless, there are indirect approaches to assess the occurrence of sex in a species, such as population studies, expression analysis of genes involved in mating processes and analysis of their selective constraints. The members of the <it>Phialocephala fortinii </it>s. l. - <it>Acephala applanata </it>species complex (PAC) are ascomycetes and the predominant dark septate endophytes that colonize woody plant roots. Despite their abundance in many ecosystems of the northern hemisphere, no sexual state has been identified to date and little is known about their reproductive biology, and how it shaped their evolutionary history and contributes to their ecological role in forest ecosystems. We therefore aimed at assessing the importance of sexual reproduction by indirect approaches that included molecular analyses of the mating type (<it>MAT</it>) genes involved in reproductive processes.</p> <p>Results</p> <p>The study included 19 PAC species and > 3, 000 strains that represented populations from different hosts, continents and ecosystems. Whereas <it>A. applanata </it>had a homothallic (self-fertile) <it>MAT </it>locus structure, all other species were structurally heterothallic (self-sterile). Compatible mating types were observed to co-occur more frequently than expected by chance. Moreover, in > 80% of the populations a 1:1 mating type ratio and gametic equilibrium were found. <it>MAT </it>genes were shown to evolve under strong purifying selection.</p> <p>Conclusions</p> <p>The signature of sex was found in worldwide populations of PAC species and functionality of <it>MAT </it>genes is likely preserved by purifying selection. We hypothesize that cryptic sex regularely occurs in the PAC and that further field studies and <it>in vitro </it>crosses will lead to the discovery of the sexual state. Although structurally heterothallic species prevail, it cannot be excluded that homothallism represents the ancestral breeding system in the PAC.</p

Suitability of Quantitative Real-Time PCR To Estimate the Biomass of Fungal Root Endophytes ▿ †

A nested single-copy locus-based quantitative PCR (qPCR) assay and a multicopy locus-based qPCR assay were developed to estimate endophytic biomass of fungal root symbionts belonging to the Phialocephala fortinii sensu lato-Acephala applanata species complex (PAC). Both assays were suitable for estimation of endophytic biomass, but the nested assay was more sensitive and specific for PAC. For mycelia grown in liquid cultures, the correlation between dry weight and DNA amount was strong and statistically significant for all three examined strains, allowing accurate prediction of fungal biomass by qPCR. For mycelia colonizing cellophane or Norway spruce roots, correlation between biomass estimated by qPCR and microscopy was strain dependent and was affected by the abundance of microsclerotia. Fungal biomass estimated by qPCR and microscopy correlated well for one strain with poor microsclerotia formation but not for two strains with high microsclerotia formation. The accuracy of qPCR measurement is constrained by the variability of cell volumes, while the accuracy of microscopy can be hampered by overlapping fungal structures and lack of specificity for PAC. Nevertheless, qPCR is preferable because it is highly specific for PAC and less time-consuming than quantification by microscopy. There is currently no better method than qPCR-based quantification using calibration curves obtained from pure mycelia to predict PAC biomass in substrates. In this study, the DNA amount of A. applanata extracted from 15 mm of Norway spruce fine root segments (mean diameter, 610 μm) varied between 0.3 and 45.5 ng, which corresponds to a PAC biomass of 5.1 ± 4.5 μg (estimate ± 95% prediction interval) and 418 ± 264 μg

Microsatellite-based quantification method to estimate biomass of endophytic Phialocephala species in strain mixtures

ISSN:1432-184XISSN:0095-362

Ready-to-use workflows for the implementation of genetic tools in conservation management

We present a conservation genetics tool kit, which offers two ready-to-use workflows for the routine application of genetic methods in conservation management. The workflows were optimized for work load and costs and are accompanied by an easy-to-read and richly illustrated manual with guidelines regarding sampling design, sampling of genetic material, necessary permits, laboratory methods, statistical analyses and documentation of results in a practice-oriented way. The manual also provides a detailed interpretation help for the implementation of the results in conservation management. One workflow deals with the identification of pond-breeding amphibians based on metabarcoding and environmental DNA (eDNA) from water samples. This workflow also discriminates the morphologically similar water frogs (Pelophylax sp.) and other closely related species (e.g. Triturus cristatus and T. carnifex). The second workflow studies connectivity among populations using microsatellite markers. Its statistical analyses encompass the detection of genetic groups and historical, recent and current dispersal and gene flow. Using the two workflows does not involve academic research institutes; they can be applied by environmental consultancies, laboratories from the private sector, governmental agencies or non-governmental organisations. These and additional conservation genetic workflows will hopefully foster the routine use of genetic methods in conservation management