Tradeoffs and constraints on the evolution of tailocins.

Phage tail-like bacteriocins (tailocins) are protein complexes produced by bacteria with the potential to kill their neighbors. Widespread throughout Gram-negative bacteria, tailocins exhibit extreme specificity in their targets, largely killing closely related strains. Despite their presence in diverse bacteria, the impact of these competitive weapons on the surrounding microbiota is largely unknown.

Continental-scale associations of Arabidopsis thaliana phyllosphere members with host genotype and drought.

Plants are colonized by distinct pathogenic and commensal microbiomes across different regions of the globe, but the factors driving their geographic variation are largely unknown. Here, using 16S ribosomal DNA and shotgun sequencing, we characterized the associations of the Arabidopsis thaliana leaf microbiome with host genetics and climate variables from 267 populations in the species' native range across Europe. Comparing the distribution of the 575 major bacterial amplicon variants (phylotypes), we discovered that microbiome composition in A.

A phage tail-like bacteriocin suppresses competitors in metapopulations of pathogenic bacteria.

Bacteria can repurpose their own bacteriophage viruses (phage) to kill competing bacteria. Phage-derived elements are frequently strain specific in their killing activity, although there is limited evidence that this specificity drives bacterial population dynamics. Here, we identified intact phage and their derived elements in a metapopulation of wild plant-associated genomes.

A weaponized phage suppresses competitors in historical and modern metapopulations of pathogenic bacteria.

Unlabelled: Bacteriophages, the viruses of bacteria, are proposed to drive bacterial population dynamics, yet direct evidence of their impact on natural populations is limited. Here we identified viral sequences in a metapopulation of wild plant-associated spp. genomes.

The genetic and physiological basis of Arabidopsis thaliana tolerance to Pseudomonas viridiflava.

The opportunistic pathogen Pseudomonas viridiflava colonizes > 50 agricultural crop species and is the most common Pseudomonas in the phyllosphere of European Arabidopsis thaliana populations. Belonging to the P. syringae complex, it is genetically and phenotypically distinct from well-characterized P.

Contrasting patterns of microbial dominance in the phyllosphere.

is one of the most abundant bacterial genera in the phyllosphere of wild , but relative to , the ecology of and its interaction with plants is poorly described. We analyzed the genomic features of over 400 isolates collected from local populations, which revealed much higher intergenomic diversity than for the considerably more uniform isolates found in the same host populations. Variation in plasmid complements and additional genomic features suggest high adaptability of this genus, and the widespread presence of protein secretion systems hints at frequent biotic interactions.

The changing influence of host genetics on the leaf fungal microbiome throughout plant development.

Host genetics and the environment influence which fungal microbes colonize a plant. A new study in PLOS Biology finds that the relative influence of these factors changes throughout the development of the biofuel crop switchgrass growing in field settings.

Commensal Pseudomonas strains facilitate protective response against pathogens in the host plant.

The community structure in the plant-associated microbiome depends collectively on host-microbe, microbe-microbe and host-microbe-microbe interactions. The ensemble of interactions between the host and microbial consortia may lead to outcomes that are not easily predicted from pairwise interactions. Plant-microbe-microbe interactions are important to plant health but could depend on both host and microbe strain variation.

Broad geographic sampling reveals the shared basis and environmental correlates of seasonal adaptation in .

To advance our understanding of adaptation to temporally varying selection pressures, we identified signatures of seasonal adaptation occurring in parallel among populations. Specifically, we estimated allele frequencies genome-wide from flies sampled early and late in the growing season from 20 widely dispersed populations. We identified parallel seasonal allele frequency shifts across North America and Europe, demonstrating that seasonal adaptation is a general phenomenon of temperate fly populations.

What natural variation can teach us about resistance durability.

Breeding a crop variety to be resistant to a pathogen usually takes years. This is problematic because pathogens, with short generation times and fluid genomes, adapt quickly to overcome resistance. The triumph of the pathogen is not inevitable, however, as there are numerous examples of durable resistance, particularly in wild plants.

Arabidopsis thaliana and Pseudomonas Pathogens Exhibit Stable Associations over Evolutionary Timescales.

Crop disease outbreaks are often associated with clonal expansions of single pathogenic lineages. To determine whether similar boom-and-bust scenarios hold for wild pathosystems, we carried out a multi-year, multi-site survey of Pseudomonas in its natural host Arabidopsis thaliana. The most common Pseudomonas lineage corresponded to a ubiquitous pathogenic clade.

Similar levels of gene content variation observed for Pseudomonas syringae populations extracted from single and multiple host species.

Bacterial strains of the same species collected from different hosts frequently exhibit differences in gene content. In the ubiquitous plant pathogen Pseudomonas syringae, more than 30% of genes encoded by each strain are not conserved among strains colonizing other host species. Although they are often implicated in host specificity, the role of this large fraction of the genome in host-specific adaptation is largely unexplored.

Mechanisms to Mitigate the Trade-Off between Growth and Defense.

Plants have evolved an array of defenses against pathogens. However, mounting a defense response frequently comes with the cost of a reduction in growth and reproduction, carrying critical implications for natural and agricultural populations. This review focuses on how costs are generated and whether and how they can be mitigated.

Differentiation between MAMP Triggered Defenses in Arabidopsis thaliana.

A first line of defense against pathogen attack for both plants and animals involves the detection of microbe-associated molecular patterns (MAMPs), followed by the induction of a complex immune response. Plants, like animals, encode several receptors that recognize different MAMPs. While these receptors are thought to function largely redundantly, the physiological responses to different MAMPs can differ in detail.

The long-term maintenance of a resistance polymorphism through diffuse interactions.

Plant resistance (R) genes are a crucial component in plant defence against pathogens. Although R genes often fail to provide durable resistance in an agricultural context, they frequently persist as long-lived balanced polymorphisms in nature. Standard theory explains the maintenance of such polymorphisms through a balance of the costs and benefits of resistance and virulence in a tightly coevolving host-pathogen pair.

Genomic variability as a driver of plant-pathogen coevolution?

Pathogens apply one of the strongest selective pressures in plant populations. Understanding plant-pathogen coevolution has therefore been a major research focus for at least sixty years [1]. Recent comparative genomic studies have revealed that the genes involved in plant defense and pathogen virulence are among the most polymorphic in the respective genomes.

Genome-wide patterns of adaptation to temperate environments associated with transposable elements in Drosophila.

Investigating spatial patterns of loci under selection can give insight into how populations evolved in response to selective pressures and can provide monitoring tools for detecting the impact of environmental changes on populations. Drosophila is a particularly good model to study adaptation to environmental heterogeneity since it is a tropical species that originated in sub-Saharan Africa and has only recently colonized the rest of the world. There is strong evidence for the adaptive role of Transposable Elements (TEs) in the evolution of Drosophila, and TEs might play an important role specifically in adaptation to temperate climates.