Papers by Marco Alexandre Guerreiro
Environmental Science and Pollution Research , 2023
Worldwide, the environmental nitrate (NO 3 −) problem is increasingly coming into focus. These in... more Worldwide, the environmental nitrate (NO 3 −) problem is increasingly coming into focus. These increases in NO 3 − concentration result mainly from agricultural inputs and are further exacerbated by decreasing and finite geogenic NO 3 − degradation capacity in aquifers. Thus, treatment methods are becoming more and more important. In this study, the effects of enhanced denitrification with addition of organic carbon (C) on thereby autochthonous occurring microbiology and compared at room temperature as well as 10 °C were investigated. Incubation of bacteria and fungi was carried out using natural sediments without degradation capacity and groundwater with high NO 3 − concentrations. Addition of the four applied substrates (acetate, glucose, ascorbic acid, and ethanol) results in major differences in microbial community. Cooling to 10 °C changes the microbiology again. Relative abundances of bacteria are strongly influenced by temperature, which is probably the explanation for different denitrification rates. Fungi are much more sensitive to the milieu change with organic C. Different fungi taxa preferentially occur at one of the two temperature approaches. Major modifications of the microbial community are mainly observed whose denitrification rates strongly depend on the temperature effect. Therefore, we assume a temperature optimum of enhanced denitrification specific to each substrate, which is influenced by the microbiology.
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Mycological Progress, 2023
Heat resistance is the ability to survive short, extreme temperature stresses, exceeding the own ... more Heat resistance is the ability to survive short, extreme temperature stresses, exceeding the own growth temperature by far. Despite their occurrence in natural substrates and their relevance for the food and healthcare industry, the diversity of fungi with heat resistance abilities is poorly studied. Sampling of boreal forest soils in Canada in combination with a heat-shock treatment (75 °C, 30 min) yielded, among others, four heat resistant, mesophilic fungal isolates. Based on rDNA barcode sequences, the novel isolates were assigned to Basidiomycota. In this study, we use macromorphological and micromorphological observations, cultivation assays and comparative genomics for physiological characterization, interspecific differentiation, and phylogenetic placement of these isolates. A phylogeny of 38 single-copy orthologous genes, an orthology analysis, and septal pore type analysis revealed the isolates as representatives of two new basidiomycetous species of the novel class Peribolosporomycetes, a sister lineage to all other members of Ustilaginomycotina. Further genomic and phenotypic data support two different species (Peribolospora kevripleyi, Peribolospora baueri), which are heat resistant and osmotolerant.
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Mycological Progress, 2023
In forest ecosystems, decomposition is essential for carbon and nutrient cycling and therefore a ... more In forest ecosystems, decomposition is essential for carbon and nutrient cycling and therefore a key process for ecosystem functioning. During the decomposition process, litter chemistry, involved decomposer organisms, and enzymatic activity change interdependently. Chemical composition of the litter is the most complex and dynamic component in the decomposition process and therefore challenging to assess holistically. In this study, we aimed to characterize chemical shifts during decomposition and link them to changes in decomposer fungal activity. We characterized the chemical composition of freshly fallen autumn leaves of European beech (Fagus sylvatica) and the corresponding leaf litter after 1 year of decomposition by proton nuclear magnetic resonance spectroscopy. We further tested the applicability of spiking experiments for qualitative and quantitative characterization of leaves and litter chemistry. The composition and transcriptional activity of fungal communities was assessed by highthroughput Illumina sequencing in the same litter samples. We were able to distinguish freshly fallen leaves from 1-year-old litter based on their chemical composition. Chemical composition of leaves converged among regions with progressing decomposition. Fungal litter communities differed in composition among regions, but they were functionally redundant according to the expression of genes encoding litter degrading enzymes (CAZymes). Fungi of the saprotrophic genera Mycena and Chalara correlated with transcription of litter-degrading CAZymes in 1-year-old litter. Forestry measures influenced the diversity and transcription rate of the detected CAZymes transcripts in litter. Their expression was primarily predicted by composition of the soluble chemical fraction of the litter. Environmental NMR fingerprints thus proved valuable for inferring ecological contexts. We propose and discuss a holistic framework to link fungal activity, enzyme expression, and chemical composition.
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Fungal Ecology, 2022
Fungal endophytes are an integral part of the leaf microbiome of forest trees. Most of these endo... more Fungal endophytes are an integral part of the leaf microbiome of forest trees. Most of these endophytes are horizontally transmitted, however little is known about their assembly drivers. Endophytic assemblages differ in composition according to geography and host individuals. In addition, climate and genetic diversity are also reported to lead to host plant adaptation. To determine the impact of the host progeny and respective adaptation to environmental conditions on endophytic assemblages, we designed a transplantation experiment in beech trees (Fagus sylvatica). Beech nuts were collected from distant geographical regions and germinated in a common greenhouse. One-year-old beech seedlings were transplanted to the different locations and the leaf-endophytic assemblages were characterized in the second growth season after planting by cultivation-independent metabarcoding. The chlorophyll and flavonoid content of the respective leaves were also measured. The results revealed host progeny effects in shaping leaf-endophytic fungal assemblages, that might be concealed by major geographical effects. We hypothesise and discuss possible interactions of different assembly drivers.
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Water Resources Research, 2021
Widespread groundwater pollution with nitrate (NO3−) and the finite and decreasing geogenic NO3− ... more Widespread groundwater pollution with nitrate (NO3−) and the finite and decreasing geogenic NO3− degradation capacity in aquifers require a better understanding of potential treatment methods. This project aimed at exploring and comparing the efficiency of four organic substances as electron donors for heterotrophic denitrification. Circulation column experiments using sediment without NO3− degradation capacity and high agricultural NO3− groundwater were conducted. Acetate, glucose, ascorbic acid, and ethanol were added to these columns in three concentration steps to induce biological denitrification, whereby also temperature dependence of denitrification rates (room temperature and typical groundwater temperature of 10°C) was taken into account. Results show denitrification with all four carbon (C) sources with intensities varying considerably between electron donors. Comparison of the two temperature approaches shows substantial differences between applied organic substances and indicates T as an important variable for denitrification. Ethanol is clearly the most effective electron donor for biodenitrification in groundwater investigated in this study, with a stronger and more effective NO3− degradation at 10°C than at room temperature. In contrast, much higher reaction rates are achieved with glucose at room temperature, compared to 10°C. Denitrification with ascorbic acid is very low at both temperatures; its addition produces biomass which repeatedly led to column clogging. In the entire test series, nitrite (NO2−) accumulation occurred more frequently and in higher concentrations at 10°C. Analysis of microorganisms shows a strong modification in microbial community in reaction to the addition of different organic C as well as between the two temperature approaches.
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G3 Genes|Genomes|Genetics
The Tremellomycetes are a species-rich group within the basidiomycete fungi; however, most analys... more The Tremellomycetes are a species-rich group within the basidiomycete fungi; however, most analyses of this group to date have focused on pathogenic Cryptococcus species within the order Tremellales. Recent genome-assisted studies of other Tremellomycetes have identified interesting features with respect to biotechnological applications as well as the evolution of genes involved in mating and sexual development. Here, we report genome sequences of two strains of Filobasidium floriforme, a species from the order Filobasidiales, which branches basally to the Tremellales, Trichosporonales and Holtermanniales. The assembled genomes of strains CBS6241 and CBS6242 are 27.4 Mb and 26.4 Mb in size, respectively, with 8314 and 7695 predicted protein-coding genes. Overall sequence identity at nucleic acid level between the strains is 97%. Among the predicted genes are pheromone precursor and pheromone receptor genes as well as two genes encoding homedomain (HD) transcription factors, which ar...
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Life, 2021
Symbiotic foliar fungal endophytes can have beneficial effects on host trees and might alleviate ... more Symbiotic foliar fungal endophytes can have beneficial effects on host trees and might alleviate climate-induced stressors. Whether and how the community of foliar endophytes is dependent on the tree neighborhood is still under debate with contradicting results from different tree diversity experiments. Here, we present our finding regarding the effect of the tree neighborhood from the temperate, densely planted and 12-years-old Kreinitz tree diversity experiment. We used linear models, redundancy analysis, Procrustes analysis and Holm-corrected multiple t-tests to quantify the effects of the plot-level tree neighborhood on the diversity and composition of foliar fungal endophytes in Fagus sylvatica, Quercus petraea and Picea abies. Against our expectations, we did not find an effect of tree diversity on endophyte diversity. Endophyte composition, however, was driven by the identity of the host species. Thirteen endophytes where overabundant in tree species mixtures, which might indicate frequent spillover or positive interactions between foliar endophytes. The independence of the diversity of endophytes from the diversity of tree species might be attributed to the small plot size and the high density of tree individuals. However, the mechanistic causes for these cryptic relationships still remain to be uncovered.
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Mycological Progress, 2021
Thermophilic, thermotolerant and heat-resistant fungi developed different physiological traits, e... more Thermophilic, thermotolerant and heat-resistant fungi developed different physiological traits, enabling them to sustain or even flourish under elevated temperatures, which are life-hostile for most other eukaryotes. With the growing demand of heat-stable molecules in biotechnology and industry, the awareness of heat-adapted fungi as a promising source of respective enzymes and biomolecules is still increasing. The aim of this study was to test two different strategies for the efficient isolation and identification of distinctly heat-adapted fungi from easily accessible substrates and locations. Eight compost piles and ten soil sites were sampled in combination with different culture-dependent approaches to describe suitable strategies for the isolation and selection of thermophilous fungi. Additionally, an approach with a heat-shock treatment, but without elevated temperature incubation led to the isolation of heat-resistant mesophilic species. The cultures were identified based on morphology, DNA barcodes, and microsatellite fingerprinting. In total, 191 obtained isolates were assigned to 31 fungal species, from which half are truly thermophilic or thermotolerant, while the other half are heat-resistant fungi. A numerous amount of heat-adapted fungi was isolated from both compost and soil samples, indicating the suitability of the used approaches and that the richness and availability of those organisms in such environments are substantially high.
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BMC Evolutionary Biology, 2020
Background
Hybridization is a central mechanism in evolution, producing new species or introducin... more Background
Hybridization is a central mechanism in evolution, producing new species or introducing important genetic variation into existing species. In plant-pathogenic fungi, adaptation and specialization to exploit a host species are key determinants of evolutionary success. Here, we performed experimental crosses between the two pathogenic Microbotryum species, M. lychnidis-dioicae and M. silenes-acaulis that are specialized to different hosts. The resulting offspring were analyzed on phenotypic and genomic levels to describe genomic characteristics of hybrid offspring and genetic factors likely involved in host-specialization.
Results
Genomic analyses of interspecific fungal hybrids revealed that individuals were most viable if the majority of loci were inherited from one species. Interestingly, species-specific loci were strictly controlled by the species’ origin of the mating type locus. Moreover we detected signs of crossing over and chromosome duplications in the genomes of the analyzed hybrids. In Microbotryum, mitochondrial DNA was found to be uniparentally inherited from the a2 mating type. Genome comparison revealed that most gene families are shared and the majority of genes are conserved between the two species, indicating very similar biological features, including infection and pathogenicity processes. Moreover, we detected 211 candidate genes that were retained under host-driven selection of backcrossed lines. These genes and might therefore either play a crucial role in host specialization or be linked to genes that are essential for specialization.
Conclusion
The combination of genome analyses with experimental selection and hybridization is a promising way to investigate host-pathogen interactions. This study manifests genetic factors of host specialization that are required for successful biotrophic infection of the post-zygotic stage, but also demonstrates the strong influence of intra-genomic conflicts or instabilities on the viability of hybrids in the haploid host-independent stage.
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FEMS Microbiology Ecology, 2019
Forest litter harbors complex networks of microorganisms whose major components are bacteria, fun... more Forest litter harbors complex networks of microorganisms whose major components are bacteria, fungi and protists. Protists, being highly selective consumers of bacteria and fungi could influence decomposition processes by shifting competitive microbial interactions. We investigated the eukaryotic diversity from 18 samples of one-year beech (Fagus sylvatica) leaf litter by RNA-based high-throughput sequencing of the small-subunit ribosomal RNA gene. By applying a metatranscriptomics approach, we avoided biases inherent to PCR-based methods, and could therefore focus on elusive protistan groups. We obtained 14 589 eukaryotic assembled sequences (contigs) representing 2223 unique taxa. Fungi dominated the eukaryotic assemblage, followed by an equal proportion of protists and plants. Among protists, the phylum Amoebozoa clearly dominated, representing more than twice the proportion of Alveolata (mostly ciliates) and Rhizaria (mostly Cercozoa), which are often retrieved as the dominant protistan groups in soils, revealing potential primer biases. By assigning functional traits to protists, we could assess that the proportion of free-living and heterotrophs was much higher than that of parasites and autotrophs, opening the way to a better understanding of the role played by the protistan communities and how biodiversity interacts with decomposition processes.
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Asian Journal of Mycology, Dec 29, 2018
DNA-metabarcoding of the fungal communities in environmental samples has greatly enhanced our kno... more DNA-metabarcoding of the fungal communities in environmental samples has greatly enhanced our knowledge of fungal diversity. However, linking taxonomic information to fungal traits is often challenging because of the immense species diversity encountered in most samples. This complicates inferring functional roles in ecosystem processes from biodiversity patterns. We have therefore made ecological traits of Ascomycete genera, compiled in a previous study, digitally accessible and searchable.
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Epichloë endophytes associated with cool-season grass species can protect their hosts from herbiv... more Epichloë endophytes associated with cool-season grass species can protect their hosts from herbivory and can suppress mycorrhizal colonization of the hosts' roots. However, little is known about whether or not Epichloë endophyte infection can also change the foliar fungal assemblages of the host. We tested 52 grassland study sites along a land-use intensity gradient in three study regions over two seasons (spring vs. summer) to determine whether Epichloë infection of the host grass Lolium perenne changes the fungal community structure in leaves. Foliar fungal communities were assessed by Next Generation Sequencing of the ITS rRNA gene region. Fungal community structure was strongly affected by study region and season in our study, while land-use intensity and infection with Epichloë endophytes had no significant effects. We conclude that effects on non-systemic endophytes resulting from land use practices and Epichloë infection reported in other studies were masked by local and seasonal variability in this study's grassland sites.
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The ecological significance of fungi occurring asymptomatically inside living plant leaves is poo... more The ecological significance of fungi occurring asymptomatically inside living plant leaves is poorly understood. Given the broad saprotrophic potential of many endophytic fungi, we hypothesized that they persist in decaying litter for an extended period of time after leaf abscission. Fungal assemblages were assessed by high-throughput sequencing in autumn leaves of beech (Fagus sylvatica) and in the corresponding leaf litter in 388 samples from 22 beech forest plots in three widely distant regions of Germany. A considerable proportion of the leaf-endophytic fungi was also found in 1-year-old litter. Co-occurrence networks revealed that the fungi formed unstructured assemblages inside the living leaves, rather than well-structured communities. Previously endophytic fungi constituted an integral part of the fungal litter community and were by far the most active fungi in 1-year-old litter. We therefore consider these endophytic occurrences to represent transient stages. Composition of the above-ground microbiome appears therefore to be closely connected to the process of litter decomposition. Considering the respective linked fungal habitat will facilitate predicting nutrient and carbon cycling and storage in forest ecosystems as well as elucidating the ecology of leaf microbiomes.
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ABSTRACT Complete species recovery and robust species identification are both crucial for accurat... more ABSTRACT Complete species recovery and robust species identification are both crucial for accurate biodiversity assessment of yeasts in the environment. We set out to analyse the relationship between species richness values in soils and sampling at several hierarchical levels: (i) different plots within a forest sampled in the same season, (ii) forests of the same type studied in the same season, and (iii) forests of the same type studied in different seasons. By using species richness estimations, we determined the adequate sampling effort in a habitat. Our results revealed that yeast communities in soils are: (1) generally species-poor in a single plot; (2) highly dissimilar between plots or across spatial and environmental transects; (3) globally diverse with up to 25% more species discovered with every new forest or season sampled; (4) understudied and may contain up to 20% hitherto undescribed species. Furthermore, we assessed species boundaries in several clades of Tremellomycetes and tested for the presence of cryptic species from the same environments using multi-locus sequence analysis (MLSA) approaches. Our results showed that ITS-LSU rRNA sequences are often unable to distinguish cryptic species and demonstrated the usefulness of network-based methods over tradi4onal phylogenetic trees for adequate species delimitation. This work was partly supported by Fundação para a Ciência e a Tecnologia (Portugal), projects PTDC/BIA- MIC/113051/2009, PTDC/BIA-BIC/4585/2012, PEst-OE/BIA/UI0457/2011.
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ABSTRACT Cryptococcus victoriae and C. carnescens are phenotypically indistinguishable sister spe... more ABSTRACT Cryptococcus victoriae and C. carnescens are phenotypically indistinguishable sister species that may be mistaken for C. laurentii based on phenotype. Phylogenetic separation between C. victoriae and C. carnescens was based on LSU and ITS sequence analyses, but very little is known on their intraspecific genetic variability or population structure. In the present study we examined 100 strains of the two species from different substrates and geographic locations, and used an MLST approach to assess genetic variation and re-examine species boundaries. The following six loci were chosen for sequencing: the LSU rRNA gene (D1/D2 domains), the ITS region, the IGS1 spacer, and fragments of the genes encoding the largest subunit of RNA polymerase II (RPB1), second largest subunit of RNA polymerase II (RPB2) and translation elongation factor 1 alpha (TEF1). We performed separate phylogenetic analyses to determine the discriminatory power of each locus. Amplification of IGS1 was inconsistent and the few sequences obtained were apparently not species-specific, while TEF1 was highly variable and intron number and position varied among strains of the same species. However, TEF1 coding sequences were too conserved and not informative. IGS1 and TEF1 were therefore not included in the MLST analysis. The RPB1 gene fragment showed the highest inter- and intraspecific variability (56 and 31 alleles in C. victoriae and C. carnescens, respectively), while LSU showed the highest conservation (5 alleles for each species). Phylogenetic network analyses of the concatenated sequences of four loci confirmed the genetic separation of the two species and revealed two additional related undescribed species. Our analyses also showed a high degree of genetic heterogeneity within C. victoriae, but the relationship between the different lineages was not clearly resolved and further analyses are required to define the limits of this species. In contrast, C. carnescens was more homogenous and a group of two strains formed a clearly separate lineage that may represent an undescribed species. Geographic origin and substrate of isolation did not reflect the phylogenetic relationships of strains from either species. Our results emphasize the importance of studying large numbers of strains and argue against using single barcode markers to determine species boundaries, which should rely on multigene approaches. Work funded by FCT – Fundação para a Ciência e a Tecnologia (PTDC/BIA-MIC/113051/2009)
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Cryptococcus flavescens and C. terrestris are phenotypically undistinguishable sister species, wh... more Cryptococcus flavescens and C. terrestris are phenotypically undistinguishable sister species, which may be mistaken for C. laurentii based on phenotype. Phylogenetic separation between C. flavescens and C. terrestris was based on LSU and ITS sequence analyses, but very little is known on their intraspecific genetic variability or population structure. In the present study we studied 50 strains of the two species from different substrates and geographic locations, and used an MLST approach to assess genetic variation and reexamine species boundaries. The following five loci were chosen for sequencing: the LSU rRNA gene (D1/D2 domains), the ITS region, the IGS1 spacer, and fragments of the genes encoding the largest subunit of RNA polymerase II (RPB1) and translation elongation factor 1 alpha (TEF1). We performed separate phylogenetic analyses to determine the discriminatory power of each locus. The TEF gene fragment showed the highest inter- and intraspecific variability (23 alleles...
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Complete species recovery and robust species identification are both crucial for accurate biodive... more Complete species recovery and robust species identification are both crucial for accurate biodiversity assessment of yeasts in the environment. We set out to analyse the relationship between species richness values in soils and sampling at several hierarchical levels: (i) different plots within a forest sampled in the same season, (ii) forests of the same type studied in the same season, and (iii) forests of the same type studied in different seasons. By using species richness estimations, we determined the adequate sampling effort in a habitat. Our results revealed that yeast communities in soils are: (1) generally species-poor in a single plot; (2) highly dissimilar between plots or across spatial and environmental transects; (3) globally diverse with up to 25% more species discovered with every new forest or season sampled; (4) understudied and may contain up to 20% hitherto undescribed species. Furthermore, we assessed species boundaries in several clades of Tremellomycetes and ...
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Cryptococcus victoriae and C. carnescens are phenotypically indistinguishable sister species that... more Cryptococcus victoriae and C. carnescens are phenotypically indistinguishable sister species that may be mistaken for C. laurentii based on phenotype. Phylogenetic separation between C. victoriae and C. carnescens was based on LSU and ITS sequence analyses, but very little is known on their intraspecific genetic variability or population structure. In the present study we examined 100 strains of the two species from different substrates and geographic locations, and used an MLST approach to assess genetic variation and re-examine species boundaries. The following six loci were chosen for sequencing: the LSU rRNA gene (D1/D2 domains), the ITS region, the IGS1 spacer, and fragments of the genes encoding the largest subunit of RNA polymerase II (RPB1), second largest subunit of RNA polymerase II (RPB2) and translation elongation factor 1 alpha (TEF1). We performed separate phylogenetic analyses to determine the discriminatory power of each locus. Amplification of IGS1 was inconsistent ...
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During a survey of yeasts vectored by migratory birds in the Mediterranean basin, isolations from... more During a survey of yeasts vectored by migratory birds in the Mediterranean basin, isolations from the cloacae of members of the order Passeriformes collected in Ustica (Italy) were performed. Based on phylogenetic analysis of the D1/D2 domain of the 26S rRNA gene and the internal transcribed spacer ITS1-5.8S rRNA gene-ITS2 region, five yeast isolates clustered in a new lineage within the Microstromatales clade. The DNA sequences of these isolates differed from those of their closest relatives, Jaminaea angkorensis and Jaminaea lanaiensis, by 20 and 25 nt substitutions in the D1/D2 domain and 119 and 131 nt substitutions in the complete ITS region, respectively. In addition, the five isolates showed phenotypic characteristics not observed in their closest relatives, such as the ability to grow at 44 8C and at pH 2.5, which suggests a possible adaptation to the bird gastrointestinal tract. On the basis of the isolation source, phenotypic features and molecular strain typing carried out with randomly amplified polymorphic DNA (RAPD)-PCR and mini-satellite-primed (MSP)-PCR analysis, the five isolates were characterized as five distinct strains of a novel species formally described as Jaminaea phylloscopi sp. nov., with 551B6 T (5PYCC 6783 T 5CBS 14087 T) as the type strain. The Mycobank accession number is MB811984.
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Papers by Marco Alexandre Guerreiro
Hybridization is a central mechanism in evolution, producing new species or introducing important genetic variation into existing species. In plant-pathogenic fungi, adaptation and specialization to exploit a host species are key determinants of evolutionary success. Here, we performed experimental crosses between the two pathogenic Microbotryum species, M. lychnidis-dioicae and M. silenes-acaulis that are specialized to different hosts. The resulting offspring were analyzed on phenotypic and genomic levels to describe genomic characteristics of hybrid offspring and genetic factors likely involved in host-specialization.
Results
Genomic analyses of interspecific fungal hybrids revealed that individuals were most viable if the majority of loci were inherited from one species. Interestingly, species-specific loci were strictly controlled by the species’ origin of the mating type locus. Moreover we detected signs of crossing over and chromosome duplications in the genomes of the analyzed hybrids. In Microbotryum, mitochondrial DNA was found to be uniparentally inherited from the a2 mating type. Genome comparison revealed that most gene families are shared and the majority of genes are conserved between the two species, indicating very similar biological features, including infection and pathogenicity processes. Moreover, we detected 211 candidate genes that were retained under host-driven selection of backcrossed lines. These genes and might therefore either play a crucial role in host specialization or be linked to genes that are essential for specialization.
Conclusion
The combination of genome analyses with experimental selection and hybridization is a promising way to investigate host-pathogen interactions. This study manifests genetic factors of host specialization that are required for successful biotrophic infection of the post-zygotic stage, but also demonstrates the strong influence of intra-genomic conflicts or instabilities on the viability of hybrids in the haploid host-independent stage.
Hybridization is a central mechanism in evolution, producing new species or introducing important genetic variation into existing species. In plant-pathogenic fungi, adaptation and specialization to exploit a host species are key determinants of evolutionary success. Here, we performed experimental crosses between the two pathogenic Microbotryum species, M. lychnidis-dioicae and M. silenes-acaulis that are specialized to different hosts. The resulting offspring were analyzed on phenotypic and genomic levels to describe genomic characteristics of hybrid offspring and genetic factors likely involved in host-specialization.
Results
Genomic analyses of interspecific fungal hybrids revealed that individuals were most viable if the majority of loci were inherited from one species. Interestingly, species-specific loci were strictly controlled by the species’ origin of the mating type locus. Moreover we detected signs of crossing over and chromosome duplications in the genomes of the analyzed hybrids. In Microbotryum, mitochondrial DNA was found to be uniparentally inherited from the a2 mating type. Genome comparison revealed that most gene families are shared and the majority of genes are conserved between the two species, indicating very similar biological features, including infection and pathogenicity processes. Moreover, we detected 211 candidate genes that were retained under host-driven selection of backcrossed lines. These genes and might therefore either play a crucial role in host specialization or be linked to genes that are essential for specialization.
Conclusion
The combination of genome analyses with experimental selection and hybridization is a promising way to investigate host-pathogen interactions. This study manifests genetic factors of host specialization that are required for successful biotrophic infection of the post-zygotic stage, but also demonstrates the strong influence of intra-genomic conflicts or instabilities on the viability of hybrids in the haploid host-independent stage.