Pinpointing genes underlying annual/perennial transitions with comparative genomics.

BACKGROUND: Transitions between perennial and an annual life history occur often in plant lineages, but the genes that control whether a plant is an annual or perennial are largely unknown. To identify genes that confer differences between annuals and perennials we compared the gene content of four pairs of sister lineages (Arabidopsis thaliana/Arabidopsis lyrata, Arabis montbretiana/Arabis alpina, Arabis verna/Aubrieta parviflora and Draba nemorosa/Draba hispanica) in the Brassicaceae in which each pair contains one annual and one perennial, plus one extra annual species (Capsella rubella). RESULTS: After sorting all genes in all nine species into gene families, we identified five families in which well-annotated genes are present in the perennials A. lyrata and A. alpina, but are not present in any of the annual species. For the eleven genes in perennials in these families, an orthologous pseudogene or otherwise highly diverged gene was found in the syntenic region of the annual species in six cases. The five candidate families identified encode: a kinase, an oxidoreductase, a lactoylglutathione lyase, a F-box protein and a zinc finger protein. By comparing the active gene in the perennial to the pseudogene or heavily altered gene in the annual, dN and dS were calculated. The low dN/dS values in one kinase suggest that it became pseudogenized more recently, while the other kinase, F-box, oxidoreductase and zinc-finger became pseudogenized closer to the divergence between the annual-perennial pair. CONCLUSIONS: We identified five gene families that may be involved in the life history switch from perennial to annual. Considering the dN and dS data and whether syntenic pseudogenes were found and the potential functions of the genes, the F-box family is considered the most promising candidate for future functional studies to determine if it affects life history.

Phylogeny-wide analysis of social amoeba genomes highlights ancient origins for complex intercellular communication.

Dictyostelium discoideum (DD), an extensively studied model organism for cell and developmental biology, belongs to the most derived group 4 of social amoebas, a clade of altruistic multicellular organisms. To understand genome evolution over long time periods and the genetic basis of social evolution, we sequenced the genomes of Dictyostelium fasciculatum (DF) and Polysphondylium pallidum (PP), which represent the early diverging groups 1 and 2, respectively. In contrast to DD, PP and DF have conventional telomere organization and strongly reduced numbers of transposable elements. The number of protein-coding genes is similar between species, but only half of them comprise an identifiable set of orthologous genes. In general, genes involved in primary metabolism, cytoskeletal functions and signal transduction are conserved, while genes involved in secondary metabolism, export, and signal perception underwent large differential gene family expansions. This most likely signifies involvement of the conserved set in core cell and developmental mechanisms, and of the diverged set in niche- and species-specific adaptations for defense and food, mate, and kin selection. Phylogenetic dating using a concatenated data set and extensive loss of synteny indicate that DF, PP, and DD split from their last common ancestor at least 0.6 billion years ago.

Creation of a structured molecular genomics report for Germany as a local adaption of HL7's Genomic Reporting Implementation Guide.

OBJECTIVE: The objective was to develop a dataset definition, information model, and FHIR® specification for key data elements contained in a German molecular genomics (MolGen) report to facilitate genomic and phenotype integration in electronic health records. MATERIALS AND METHODS: A dedicated expert group participating in the German Medical Informatics Initiative reviewed information contained in MolGen reports, determined the key elements, and formulated a dataset definition. HL7's Genomics Reporting Implementation Guide (IG) was adopted as a basis for the FHIR® specification which was subjected to a public ballot. In addition, elements in the MolGen dataset were mapped to the fields defined in ISO/TS 20428:2017 standard to evaluate compliance. RESULTS: A core dataset of 76 data elements, clustered into 6 categories was created to represent all key information of German MolGen reports. Based on this, a FHIR specification with 16 profiles, 14 derived from HL7®'s Genomics Reporting IG and 2 additional profiles (of the FamilyMemberHistory and RiskAssessment resources), was developed. Five example resource bundles show how our adaptation of an international standard can be used to model MolGen report data that was requested following oncological or rare disease indications. Furthermore, the map of the MolGen report data elements to the fields defined by the ISO/TC 20428:2017 standard, confirmed the presence of the majority of required fields. CONCLUSIONS: Our report serves as a template for other research initiatives attempting to create a standard format for unstructured genomic report data. Use of standard formats facilitates integration of genomic data into electronic health records for clinical decision support.

Origin of land plants: do conjugating green algae hold the key?

BACKGROUND: The terrestrial habitat was colonized by the ancestors of modern land plants about 500 to 470 million years ago. Today it is widely accepted that land plants (embryophytes) evolved from streptophyte algae, also referred to as charophycean algae. The streptophyte algae are a paraphyletic group of green algae, ranging from unicellular flagellates to morphologically complex forms such as the stoneworts (Charales). For a better understanding of the evolution of land plants, it is of prime importance to identify the streptophyte algae that are the sister-group to the embryophytes. The Charales, the Coleochaetales or more recently the Zygnematales have been considered to be the sister group of the embryophytes However, despite many years of phylogenetic studies, this question has not been resolved and remains controversial. RESULTS: Here, we use a large data set of nuclear-encoded genes (129 proteins) from 40 green plant taxa (Viridiplantae) including 21 embryophytes and six streptophyte algae, representing all major streptophyte algal lineages, to investigate the phylogenetic relationships of streptophyte algae and embryophytes. Our phylogenetic analyses indicate that either the Zygnematales or a clade consisting of the Zygnematales and the Coleochaetales are the sister group to embryophytes. CONCLUSIONS: Our analyses support the notion that the Charales are not the closest living relatives of embryophytes. Instead, the Zygnematales or a clade consisting of Zygnematales and Coleochaetales are most likely the sister group of embryophytes. Although this result is in agreement with a previously published phylogenetic study of chloroplast genomes, additional data are needed to confirm this conclusion. A Zygnematales/embryophyte sister group relationship has important implications for early land plant evolution. If substantiated, it should allow us to address important questions regarding the primary adaptations of viridiplants during the conquest of land. Clearly, the biology of the Zygnematales will receive renewed interest in the future.

Centromere sequence and dynamics in Dictyostelium discoideum.

Centromeres play a pivotal role in the life of a eukaryote cell, perform an essential and conserved function, but this has not led to a standard centromere structure. It remains currently unclear, how the centromeric function is achieved by widely differing structures. Since centromeres are often large and consist mainly of repetitive sequences they have only been analyzed in great detail in a handful of organisms. The genome of Dictyostelium discoideum, a valuable model organism, was described a few years ago but its centromere organization remained largely unclear. Using available sequence information we reconstructed the putative centromere organization in three of the six chromosomes of D. discoideum. They mainly consist of one type of transposons that is confined to centromeric regions. Centromeres are dynamic due to transposon integration, but an optimal centromere size seems to exist in D. discoideum. One centromere probably has expanded recently, whereas another underwent major rearrangements. In addition to insights into the centromere organization and dynamics of a protist eukaryote, this work also provides a starting point for the analysis of the evolution of centromere structures in social amoebas by comparative genomics.

Transcriptome analysis of the sex pheromone gland of the noctuid moth Heliothis virescens.

BACKGROUND: The chemical components of sex pheromones have been determined for more than a thousand moth species, but so far only a handful of genes encoding enzymes responsible for the biosynthesis of these compounds have been identified. For understanding the evolution of moth sexual communication, it is essential to know which genes are involved in the production of specific pheromone components and what controls the variation in their relative frequencies in the pheromone blend. We used a transcriptomic approach to characterize the pheromone gland of the Noctuid moth Heliothis virescens, an important agricultural pest, in order to obtain substantial general sequence information and to identify a range of candidate genes involved in the pheromone biosynthetic pathway. RESULTS: To facilitate identifying sets of genes involved in a broad range of processes and to capture rare transcripts, we developed our majority of ESTs from a normalized cDNA library of Heliothis virescens pheromone glands (PG). Combining these with a non-normalized library yielded a total of 17,233 ESTs, which assembled into 2,082 contigs and 6,228 singletons. Using BLAST searches of the NR and Swissprot databases we were able to identify a large number of putative unique gene elements (unigenes), which we compared to those derived from previous transcriptomic surveys of the larval stage of Heliothis virescens. The distribution of unigenes among GO Biological Process functional groups shows an overall similarity between PG and larval transcriptomes, but with distinct enrichment of specific pathways in the PG. In addition, we identified a large number of candidate genes in the pheromone biosynthetic pathways. CONCLUSION: These data constitute one of the first large-scale EST-projects for Noctuidae, a much-needed resource for exploring these pest species. Our analysis shows a surprisingly complex transcriptome and we identified a large number of potential pheromone biosynthetic pathway and immune-related genes that can be applied to population and systematic studies of Heliothis virescens and other Noctuidae.

Multilocus patterns of nucleotide diversity, population structure and linkage disequilibrium in Boechera stricta, a wild relative of Arabidopsis.

Information about polymorphism, population structure, and linkage disequilibrium (LD) is crucial for association studies of complex trait variation. However, most genomewide studies have focused on model systems, with very few analyses of undisturbed natural populations. Here, we sequenced 86 mapped nuclear loci for a sample of 46 genotypes of Boechera stricta and two individuals of B. holboellii, both wild relatives of Arabidopsis. Isolation by distance was significant across the species range of B. stricta, and three geographic groups were identified by structure analysis, principal coordinates analysis, and distance-based phylogeny analyses. The allele frequency spectrum indicated a genomewide deviation from an equilibrium neutral model, with silent nucleotide diversity averaging 0.004. LD decayed rapidly, declining to background levels in approximately 10 kb or less. For tightly linked SNPs separated by <1 kb, LD was dependent on the reference population. LD was lower in the specieswide sample than within populations, suggesting that low levels of LD found in inbreeding species such as B. stricta, Arabidopsis thaliana, and barley may result from broad geographic sampling that spans heterogeneous genetic groups. Finally, analyses also showed that inbreeding B. stricta and A. thaliana have approximately 45% higher recombination per kilobase than outcrossing A. lyrata.

Population history in Arabidopsis halleri using multilocus analysis.

A. halleri is a psuedometallophyte with a patchy distribution in Europe and is often spread by human activity. To determine the population history and whether this history is consistent with potential human effects, we surveyed nucleotide variation using 24 loci from 12 individuals in a large A. halleri population. The means of total and silent nucleotide variation (theta(W)) are within the range expected for the species. The population genetic neutrality tests Tajima's D and Wall's B had significant composite results rejecting panmixia, and Approximate Bayesian Computation analysis revealed that a subdivision model better explained the variation than the standard neutral model, refugia (or admixture), bottleneck or change of population size models. A categorical regression analysis further supports the subdivision model, and under the subdivision model, the neutrality tests are no longer significant. The best support was for two source populations, a situation consistent with the mixing of two populations possibly mediated by human activity. This scenario might limit the genetic diversity and adaptive potential of the population. The non-neutral population variation described here should be considered in bioinformatic searches for adaptation.

Mitochondrial genome evolution in the social amoebae.

Most mitochondria contain a core set of genes required for mitochondrial function, but beyond this base there are variable genomic features. The mitochondrial genome of the model species Dictyostelium discoideum demonstrated that the social amoebae mitochondrial genomes have a size between those of metazoans and plants, but no comparative study of social amoebae mitochondria has been performed. Here, we present a comparative analysis of social amoebae mitochondrial genomes using D. discoideum, Dictyostelium citrinum, Dictyostelium fasciculatum, and Polysphondylium pallidum. The social amoebae mitochondria have similar sizes, AT content, gene content and have a high level of synteny except for one segmental rearrangement and extensive displacement of tRNAs. From the species that contain the rearrangement, it can be concluded that the event occurred late in the evolution of social amoebae. A phylogeny using 36 mitochondrial genes produced a well-supported tree suggesting that the pairs of D. discoideum/D. citrinum and D. fasciculatum/P. pallidum are sister species although the position of the root is not certain. Group I introns and endonucleases are variable in number and location in the social amoebae. Phylogenies of the introns and endonucleases suggest that there have been multiple recent duplications or extinctions and confirm that endonucleases have the ability to insert into new areas. An analysis of dN/dS ratios in mitochondrial genes revealed that among groups of genes, adenosine triphosphate synthase complex genes have the highest ratio, whereas cytochrome oxidase and nicotinamide adenine dinucleotide (NADH) dehydrogenase genes had the lowest ratio. The genetic codes of D. citrinum, P. pallidum, and D. fasciculatum are the universal code although D. fasciculatum does not use the TGA stop codon. In D. fasciculatum, we demonstrate for the first time that a mitochondrial genome without the TGA stop codon still uses the release factor RF2 that recognizes TGA. Theories of how the genetic code can change and why RF2 may be a constraint against switching codes are discussed.

Approaching Clinical Data Transformation from Disparate Healthcare IT Systems Through a Modular Framework.

Many healthcare IT systems in Germany are unable to interoperate with other systems through standardised data formats. Therefore it is difficult to store and retrieve data and to establish a systematic collection of data with provenance across systems and even healthcare institutions. We outline the concept for a Transformation Pipeline that can act as a processor for proprietary medical data formats from multiple sources. Through a modular construction, the pipeline relies on different data extraction and data enrichment modules as well as on interfaces to external definitions for interoperability standards. The developed solution is extendable and reusable, enabling data transformation independent from current format definitions and entailing the opportunity of collaboration with other research groups.

Fitness benefits of systemic acquired resistance during Hyaloperonospora parasitica infection in Arabidopsis thaliana.

We investigated the fitness benefits of systemic acquired resistance (SAR) in Arabidopsis thaliana using a mutational and transformational genetic approach. Genetic lines were designed to differ in the genes determining resistance signaling in a common genetic background. Two mutant lines (cpr1 and cpr5) constitutively activate SAR at different points in SAR signaling, and one mutant line (npr1) has impaired SAR. The transgenic line (NPR1-H) has enhanced resistance when SAR is activated, but SAR is still inducible similarly to wild type. The fitness benefits were also investigated under two nutrient levels to test theories that preventing pathogen damage and realized resistance benefits may be affected by nutrient availability. Under low-nutrient conditions and treatment with the pathogenic oomycete, Hyaloperonospora parasitica, wild type had a higher fitness than the mutant that could not activate SAR, demonstrating that normal inducible SAR is beneficial in these conditions; this result, however, was not found under high-nutrient conditions. The mutants with constitutive SAR all failed to show a fitness benefit in comparison to wild type under a H. parasitica pathogen treatment, suggesting that SAR is induced to prevent an excessive fitness cost.

Natural variation in MAM within and between populations of Arabidopsis lyrata determines glucosinolate phenotype.

The genetic variation that underlies the glucosinolate phenotype of Arabidopsis lyrata ssp. petraea was investigated between and within populations. A candidate glucosinolate biosynthetic locus (MAM, containing methylthioalkylmalate synthase genes) was mapped in A. lyrata to a location on linkage group 6 corresponding to the homologous location for MAM in A. thaliana. In A. thaliana MAM is responsible for side chain elongation in aliphatic glucosinolates, and the MAM phenotype can be characterized by the ratios of long- to short-chain glucosinolates. A quantitative trait loci (QTL) analysis of glucosinolate ratios in an A. lyrata interpopulation cross found one QTL at MAM. Additional QTL were identified for total indolic glucosinolates and for the ratio of aliphatic to indolic glucosinolates. MAM was then used as the candidate gene for a within-population cosegregation analysis in a natural A. lyrata population from Germany. Extensive variation in microsatellite markers at MAM was found and this variation cosegregated with the same glucosinolate ratios as in the QTL study. The combined results indicate that both between- and within-population genetic variation in the MAM region determines phenotypic variation in glucosinolate side chains in A. lyrata.

MHC-dependent mate choice is linked to a trace-amine-associated receptor gene in a mammal.

Major histocompatibility complex (MHC) genes play a pivotal role in vertebrate self/nonself recognition, parasite resistance and life history decisions. In evolutionary terms, the MHC's exceptional diversity is likely maintained by sexual and pathogen-driven selection. Even though MHC-dependent mating preferences have been confirmed for many species, the sensory and genetic mechanisms underlying mate recognition remain cryptic. Since olfaction is crucial for social communication in vertebrates, variation in chemosensory receptor genes could explain MHC-dependent mating patterns. Here, we investigated whether female mate choice is based on MHC alleles and linked to variation in chemosensory trace amine-associated receptors (TAARs) in the greater sac-winged bat (Saccopteryx bilineata). We sequenced several MHC and TAAR genes and related their variation to mating and paternity data. We found strong evidence for MHC class I-dependent female choice for genetically diverse and dissimilar males. We also detected a significant interaction between mate choice and the female TAAR3 genotype, with TAAR3-heterozygous females being more likely to choose MHC-diverse males. These results suggest that TAARs and olfactory cues may be key mediators in mammalian MHC-dependent mate choice. Our study may help identify the ligands involved in the chemical communication between potential mates.

Fitness costs of mutations affecting the systemic acquired resistance pathway in Arabidopsis thaliana.

This study investigated the fitness effects of four mutations (npr1, cpr1, cpr5, and cpr6) and two transgenic genotypes (NPR1-L and NPR1-H) affecting different points of the systemic acquired resistance (SAR) signaling pathway associated with pathogen defense in Arabidopsis thaliana. The npr1 mutation, which resulted in a failure to express SAR, had no effect on fitness under growth chamber conditions, but decreased fitness in the field. The expression of NPR1 positively correlated with the fitness in the field. Constitutive activation of SAR by cpr1, cpr5, and cpr6 generally decreased fitness in the field and under two nutrient levels in two growth chamber conditions. At low-nutrient levels, fitness differences between wild type and the constitutive mutants were unchanged or reduced (especially in cpr5). The reduced fitness of the constitutive mutants suggests that this pathway is costly, with the precise fitness consequences highly dependent on the environmental context.