Comparative genomics reveals low levels of inter- and intraspecies diversity in the causal agents of dwarf and common bunt of wheat and hint at conspecificity of Tilletia caries and T. laevis.

Tilletia caries and T. laevis, which are the causal agents of common bunt, as well as T. controversa, which causes dwarf bunt of wheat, threaten especially organic wheat farming. The three closely related fungal species differ in their teliospore morphology and partially in their physiology and infection biology. The gene content as well as intraspecies variation in these species and the genetic basis of their separation is unknown. We sequenced the genome of four T. caries, five T. controversa, and two T. laevis and extended this dataset with five publicly available ones. The genomes of the three species displayed microsynteny with up to 94.3% pairwise aligned regions excluding repetitive regions. The majority of functionally characterized genes involved in pathogenicity, life cycle, and infection of corn smut, Ustilago maydis, were found to be absent or poorly conserved in the draft genomes and the biosynthetic pathway for trimethylamine in Tilletia spp. could be different from bacteria. Overall, 75% of the identified protein-coding genes comprising 84% of the total predicted carbohydrate utilizing enzymes, 72.5% putatively secreted proteins, and 47.4% of effector-like proteins were conserved and shared across all 16 isolates. We predicted nine highly identical secondary metabolite biosynthesis gene clusters comprising in total 62 genes in all species and none were species-specific. Less than 0.1% of the protein-coding genes were species-specific and their function remained mostly unknown. Tilletia controversa had the highest intraspecies genetic variation, followed by T. caries and the lowest in T. laevis. Although the genomes of the three species are very similar, employing 241 single copy genes T. controversa was phylogenetically distinct from T. caries and T. laevis, however these two could not be resolved as individual monophyletic groups. This was in line with the genome-wide number of single nucleotide polymorphisms and small insertions and deletions. Despite the conspicuously different teliospore ornamentation of T. caries and T. laevis, a high degree of genomic identity and scarcity of species-specific genes indicate that the two species could be conspecific.

In silico screening and molecular dynamics of phytochemicals from Indian cuisine against SARS-CoV-2 MPro.

SARS-CoV-2 cause fatal infection in 213 countries accounting for the death of millions of people globally. In the present study, phytochemicals from spices were assessed for their ability to interact with SARS-CoV-2 MPro. Structure based virtual screening was performed with 146 phytochemicals from spices using Autodock Vina. Phytochemicals with binding energy ≥ -8.0 kcal/mol were selected to understand their interaction with MPro. Virtual screening was further validated by performing molecular docking to generate favorable docked poses and the participation of important amino acid residues. Molecular dynamics simulation for the docked poses was performed to study thermodynamic properties of the protein, ligand and protein-ligand complexes. The finding shows that cinnamtannin B2 and cyanin showed favorable binding affinity values with SARS-CoV-2 MPro. The results are comparable in terms of docked poses, important amino acid participation and thermodynamic properties with the standard control drugs remdesivir, benazepril and hydroxychloroquine diphosphate. Prime MM-GBSA was employed for end-point binding energy calculation. Binding to domain I and II of MPro were mediated through the OH, SH, NH2 and non-polar side chain of amino acids. Cinnamtannin B2 and cyanin binds to MPro with many sub sites within the active site with RMSD and RMSF within 4 Å. The results computed using Prime MM-GBSA show that cinnamtannin B2 (-68.54940214 kcal/mol) and cyanin (-62.1902835 kcal/mol) have better binding affinity in comparison to hydroxychloroquine diphosphate (-54.00912412 kcal/mol) and benazepril (-53.70242369 kcal/mol). The results provide a basis for exploiting cinnamtannin B2 and cyanin as a starting point potential candidate for the development of drug against SARS-CoV-2.Communicated by Ramaswamy H. Sarma.

Complete Chloroplast Genomes of Fagus sylvatica L. Reveal Sequence Conservation in the Inverted Repeat and the Presence of Allelic Variation in NUPTs.

Growing amounts of genomic data and more efficient assembly tools advance organelle genomics at an unprecedented scale. Genomic resources are increasingly used for phylogenetic analyses of many plant species, but are less frequently used to investigate within-species variability and phylogeography. In this study, we investigated genetic diversity of Fagus sylvatica, an important broadleaved tree species of European forests, based on complete chloroplast genomes of 18 individuals sampled widely across the species distribution. Our results confirm the hypothesis of a low cpDNA diversity in European beech. The chloroplast genome size was remarkably stable (158,428 ± 37 bp). The polymorphic markers, 12 microsatellites (SSR), four SNPs and one indel, were found only in the single copy regions, while inverted repeat regions were monomorphic both in terms of length and sequence, suggesting highly efficient suppression of mutation. The within-individual analysis of polymorphisms showed >9k of markers which were proportionally present in gene and non-gene areas. However, an investigation of the frequency of alternate alleles revealed that the source of this diversity originated likely from nuclear-encoded plastome remnants (NUPTs). Phylogeographic and Mantel correlation analysis based on the complete chloroplast genomes exhibited clustering of individuals according to geographic distance in the first distance class, suggesting that the novel markers and in particular the cpSSRs could provide a more detailed picture of beech population structure in Central Europe.

Genomic basis for drought resistance in European beech forests threatened by climate change.

In the course of global climate change, Central Europe is experiencing more frequent and prolonged periods of drought. The drought years 2018 and 2019 affected European beeches (Fagus sylvatica L.) differently: even in the same stand, drought-damaged trees neighboured healthy trees, suggesting that the genotype rather than the environment was responsible for this conspicuous pattern. We used this natural experiment to study the genomic basis of drought resistance with Pool-GWAS. Contrasting the extreme phenotypes identified 106 significantly associated single-nucleotide polymorphisms (SNPs) throughout the genome. Most annotated genes with associated SNPs (>70%) were previously implicated in the drought reaction of plants. Non-synonymous substitutions led either to a functional amino acid exchange or premature termination. An SNP assay with 70 loci allowed predicting drought phenotype in 98.6% of a validation sample of 92 trees. Drought resistance in European beech is a moderately polygenic trait that should respond well to natural selection, selective management, and breeding.

Climate change is having a serious impact on many ecosystems. In the summer of 2018 and 2019, around two thirds of European beech trees were damaged or killed by extreme drought. It is critical to keep these beech woods healthy, as they are central to the survival of over 6,000 other species of animals and plants. The level of damage caused by the drought varied between forests. However, not all the trees in each forest responded in the same way, with severely damaged trees often sitting next to fully healthy ones. This suggests that the genetic make-up of each tree determines how well it can adapt to drought rather than its local environment. To investigate this further, Pfenninger et al. studied the genome of over 400 European beech trees from the Hesse region in Germany. The samples came from pairs of neighbouring trees that had responded differently to the droughts. The analysis found more than 80 parts of the genome that differed between healthy and damaged trees. Pfenninger et al. then used this information to create a genetic test which can quickly and inexpensively predict how well an individual beech tree might survive in a drought. Applying this test to another 92 trees revealed that it can reliably detect which ones were healthy and which ones were damaged. Beech forests are typically managed by private owners, agencies or breeders that could use this genetic test to select and reproduce trees that are better adapted to drought. The goal now is to develop the test so that it can be used more widely to manage European beech trees and potentially other species.

A Chromosome-Level Genome Assembly of the European Beech (Fagus sylvatica) Reveals Anomalies for Organelle DNA Integration, Repeat Content and Distribution of SNPs.

The European Beech is the dominant climax tree in most regions of Central Europe and valued for its ecological versatility and hardwood timber. Even though a draft genome has been published recently, higher resolution is required for studying aspects of genome architecture and recombination. Here, we present a chromosome-level assembly of the more than 300 year-old reference individual, Bhaga, from the Kellerwald-Edersee National Park (Germany). Its nuclear genome of 541 Mb was resolved into 12 chromosomes varying in length between 28 and 73 Mb. Multiple nuclear insertions of parts of the chloroplast genome were observed, with one region on chromosome 11 spanning more than 2 Mb which fragments up to 54,784 bp long and covering the whole chloroplast genome were inserted randomly. Unlike in Arabidopsis thaliana, ribosomal cistrons are present in Fagus sylvatica only in four major regions, in line with FISH studies. On most assembled chromosomes, telomeric repeats were found at both ends, while centromeric repeats were found to be scattered throughout the genome apart from their main occurrence per chromosome. The genome-wide distribution of SNPs was evaluated using a second individual from Jamy Nature Reserve (Poland). SNPs, repeat elements and duplicated genes were unevenly distributed in the genomes, with one major anomaly on chromosome 4. The genome presented here adds to the available highly resolved plant genomes and we hope it will serve as a valuable basis for future research on genome architecture and for understanding the past and future of European Beech populations in a changing climate.

The Genome of Microthlaspi erraticum (Brassicaceae) Provides Insights Into the Adaptation to Highly Calcareous Soils.

Microthlaspi erraticum is widely distributed in temperate Eurasia, but restricted to Ca2+-rich habitats, predominantly on white Jurassic limestone, which is made up by calcium carbonate, with little other minerals. Thus, naturally occurring Microthlaspi erraticum individuals are confronted with a high concentration of Ca2+ ions while Mg2+ ion concentration is relatively low. As there is a competitive uptake between these two ions, adaptation to the soil condition can be expected. In this study, it was the aim to explore the genomic consequences of this adaptation by sequencing and analysing the genome of Microthlaspi erraticum. Its genome size is comparable with other diploid Brassicaceae, while more genes were predicted. Two Mg2+ transporters known to be expressed in roots were duplicated and one showed a significant degree of positive selection. It is speculated that this evolved due to the pressure to take up Mg2+ ions efficiently in the presence of an overwhelming amount of Ca2+ ions. Future studies on plants specialized on similar soils and affinity tests of the transporters are needed to provide unequivocal evidence for this hypothesis. If verified, the transporters found in this study might be useful for breeding Brassicaceae crops for higher yield on Ca2+-rich and Mg2+ -poor soils.

A reference genome of the European beech (Fagus sylvatica L.).

Background: The European beech is arguably the most important climax broad-leaved tree species in Central Europe, widely planted for its valuable wood. Here, we report the 542 Mb draft genome sequence of an up to 300-year-old individual (Bhaga) from an undisturbed stand in the Kellerwald-Edersee National Park in central Germany. Findings: Using a hybrid assembly approach, Illumina reads with short- and long-insert libraries, coupled with long Pacific Biosciences reads, we obtained an assembled genome size of 542 Mb, in line with flow cytometric genome size estimation. The largest scaffold was of 1.15 Mb, the N50 length was 145 kb, and the L50 count was 983. The assembly contained 0.12% of Ns. A Benchmarking with Universal Single-Copy Orthologs (BUSCO) analysis retrieved 94% complete BUSCO genes, well in the range of other high-quality draft genomes of trees. A total of 62,012 protein-coding genes were predicted, assisted by transcriptome sequencing. In addition, we are reporting an efficient method for extracting high-molecular-weight DNA from dormant buds, by which contamination by environmental bacteria and fungi was kept at a minimum. Conclusions: The assembled genome will be a valuable resource and reference for future population genomics studies on the evolution and past climate change adaptation of beech and will be helpful for identifying genes, e.g., involved in drought tolerance, in order to select and breed individuals to adapt forestry to climate change in Europe. A continuously updated genome browser and download page can be accessed from beechgenome.net, which will include future genome versions of the reference individual Bhaga, as new sequencing approaches develop.

The genome sequence of the commercially cultivated mushroom Agrocybe aegerita reveals a conserved repertoire of fruiting-related genes and a versatile suite of biopolymer-degrading enzymes.

BACKGROUND: Agrocybe aegerita is an agaricomycete fungus with typical mushroom features, which is commercially cultivated for its culinary use. In nature, it is a saprotrophic or facultative pathogenic fungus causing a white-rot of hardwood in forests of warm and mild climate. The ease of cultivation and fructification on solidified media as well as its archetypal mushroom fruit body morphology render A. aegerita a well-suited model for investigating mushroom developmental biology. RESULTS: Here, the genome of the species is reported and analysed with respect to carbohydrate active genes and genes known to play a role during fruit body formation. In terms of fruit body development, our analyses revealed a conserved repertoire of fruiting-related genes, which corresponds well to the archetypal fruit body morphology of this mushroom. For some genes involved in fruit body formation, paralogisation was observed, but not all fruit body maturation-associated genes known from other agaricomycetes seem to be conserved in the genome sequence of A. aegerita. In terms of lytic enzymes, our analyses suggest a versatile arsenal of biopolymer-degrading enzymes that likely account for the flexible life style of this species. Regarding the amount of genes encoding CAZymes relevant for lignin degradation, A. aegerita shows more similarity to white-rot fungi than to litter decomposers, including 18 genes coding for unspecific peroxygenases and three dye-decolourising peroxidase genes expanding its lignocellulolytic machinery. CONCLUSIONS: The genome resource will be useful for developing strategies towards genetic manipulation of A. aegerita, which will subsequently allow functional genetics approaches to elucidate fundamentals of fruiting and vegetative growth including lignocellulolysis.

Adaptive differentiation coincides with local bioclimatic conditions along an elevational cline in populations of a lichen-forming fungus.

BACKGROUND: Many fungal species occur across a variety of habitats. Particularly lichens, fungi forming symbioses with photosynthetic partners, have evolved remarkable tolerances for environmental extremes. Despite their ecological importance and ubiquity, little is known about the genetic basis of adaption in lichen populations. Here we studied patterns of genome-wide differentiation in the lichen-forming fungus Lasallia pustulata along an altitudinal gradient in the Mediterranean region. We resequenced six populations as pools and identified highly differentiated genomic regions. We then detected gene-environment correlations while controlling for shared population history and pooled sequencing bias, and performed ecophysiological experiments to assess fitness differences of individuals from different environments. RESULTS: We detected two strongly differentiated genetic clusters linked to Mediterranean and temperate-oceanic climate, and an admixture zone, which coincided with the transition between the two bioclimates. High altitude individuals showed ecophysiological adaptations to wetter and more shaded conditions. Highly differentiated genome regions contained a number of genes associated with stress response, local environmental adaptation, and sexual reproduction. CONCLUSIONS: Taken together our results provide evidence for a complex interplay between demographic history and spatially varying selection acting on a number of key biological processes, suggesting a scenario of ecological speciation.

Genome comparisons provide insights into the role of secondary metabolites in the pathogenic phase of the Photorhabdus life cycle.

BACKGROUND: Bacteria within the genus Photorhabdus maintain mutualistic symbioses with nematodes in complicated lifecycles that also involves insect pathogenic phases. Intriguingly, these bacteria are rich in biosynthetic gene clusters that produce compounds with diverse biological activities. As a basis to better understand the life cycles of Photorhabdus we sequenced the genomes of two recently discovered representative species and performed detailed genomic comparisons with five publically available genomes. RESULTS: Here we report the genomic details of two new reference Photorhabdus species. By then conducting genomic comparisons across the genus, we show that there are several highly conserved biosynthetic gene clusters. These clusters produce a range of bioactive small molecules that support the pathogenic phase of the integral relationship that Photorhabdus maintain with nematodes. CONCLUSIONS: Photorhabdus contain several genetic loci that allow them to become specialist insect pathogens by efficiently evading insect immune responses and killing the insect host.

Draft Genome Sequence of Ochrobactrum anthropi Strain ML7 Isolated from Soil Samples in Vinhphuc Province, Vietnam.

Ochrobactrum species are widespread in the environment and can colonize a wide variety of habitats. Here, we describe the sequencing of a new environmental isolate of Ochrobactrum anthropi isolated from northern Vietnam.

The fungal core effector Pep1 is conserved across smuts of dicots and monocots.

The secreted fungal effector Pep1 is essential for penetration of the host epidermis and establishment of biotrophy in the Ustilago maydis-maize pathosystem. Previously, Pep1 was found to be an inhibitor of apoplastic plant peroxidases, which suppresses the oxidative burst, a primary immune response of the host plant and enables fungal colonization. To investigate the conservation of Pep1 in other pathogens, genomes of related smut species were screened for pep1 orthologues. Pep1 proteins were produced in Escherichia coli for functional assays. The biological function of Pep1 was tested by heterologous expression in U. maydis and Hordeum vulgare. Pep1 orthologues revealed a remarkable degree of sequence conservation, indicating that this effector might play a fundamental role in virulence of biotrophic smut fungi. Pep1 function and its role in virulence are conserved in different pathogenic fungi, even across the monocot-dicot border of host plants. The findings described in this study classify Pep1 as a phylogenetically conserved fungal core effector. Furthermore, we documented the influence of Pep1 on the disease caused by Blumeria graminis f. sp. hordei which is a non-smut-related pathosystem.

Gene loss rather than gene gain is associated with a host jump from monocots to dicots in the Smut Fungus Melanopsichium pennsylvanicum.

Smut fungi are well-suited to investigate the ecology and evolution of plant pathogens, as they are strictly biotrophic, yet cultivable on media. Here we report the genome sequence of Melanopsichium pennsylvanicum, closely related to Ustilago maydis and other Poaceae-infecting smuts, but parasitic to a dicot plant. To explore the evolutionary patterns resulting from host adaptation after this huge host jump, the genome of Me. pennsylvanicum was sequenced and compared with the genomes of U. maydis, Sporisorium reilianum, and U. hordei. Although all four genomes had a similar completeness in CEGMA (Core Eukaryotic Genes Mapping Approach) analysis, gene absence was highest in Me. pennsylvanicum, and most pronounced in putative secreted proteins, which are often considered as effector candidates. In contrast, the amount of private genes was similar among the species, highlighting that gene loss rather than gene gain is the hallmark of adaptation after the host jump to the dicot host. Our analyses revealed a trend of putative effectors to be next to another putative effector, but the majority of these are not in clusters and thus the focus on pathogenicity clusters might not be appropriate for all smut genomes. Positive selection studies revealed that Me. pennsylvanicum has the highest number and proportion of genes under positive selection. In general, putative effectors showed a higher proportion of positively selected genes than noneffector candidates. The 248 putative secreted effectors found in all four smut genomes might constitute a core set needed for pathogenicity, whereas those 92 that are found in all grass-parasitic smuts but have no ortholog in Me. pennsylvanicum might constitute a set of effectors important for successful colonization of grass hosts.

The rise and fall of the Phytophthora infestans lineage that triggered the Irish potato famine.

Phytophthora infestans, the cause of potato late blight, is infamous for having triggered the Irish Great Famine in the 1840s. Until the late 1970s, P. infestans diversity outside of its Mexican center of origin was low, and one scenario held that a single strain, US-1, had dominated the global population for 150 years; this was later challenged based on DNA analysis of historical herbarium specimens. We have compared the genomes of 11 herbarium and 15 modern strains. We conclude that the 19th century epidemic was caused by a unique genotype, HERB-1, that persisted for over 50 years. HERB-1 is distinct from all examined modern strains, but it is a close relative of US-1, which replaced it outside of Mexico in the 20th century. We propose that HERB-1 and US-1 emerged from a metapopulation that was established in the early 1800s outside of the species' center of diversity. DOI:http://dx.doi.org/10.7554/eLife.00731.001.