Polyploidy and microbiome associations mediate similar responses to pathogens in Arabidopsis.

It has become increasingly clear that the microbiome plays a critical role in shaping the host organism's response to disease. There also exists mounting evidence that an organism's ploidy level is important in their response to pathogens and parasites. However, no study has determined whether or how these two factors influence one another. We investigate the effect of whole-genome duplication in Arabidopsis thaliana on the above-ground (phyllosphere) microbiome and determine the interacting impacts of ploidy and microbiome on disease outcome. Using seven independently derived synthetic autotetraploid Arabidopsis accessions and a synthetic leaf-associated bacterial community, we confirm that polyploids are generally more resistant to the model pathogen Pseudomonas syringae pv. Tomato DC3000. Polyploids fare better against the pathogen than diploids do, regardless of microbial inoculation, whereas diploids harboring an intact microbiome have lower pathogen densities than those without. In addition, diploids have elevated numbers of defense-related genes that are differentially expressed in the presence of their phyllosphere microbiota, whereas polyploids exhibit some constitutively activated defenses, regardless of colonization by the synthetic community. These results imply that whole-genome duplication can enhance immunity, resulting in a decreased dependence on the microbiome for protection against pathogens.

Whole genome duplication and dispersed duplication characterize the evolution of the plant PINOID gene family across plant species.

PINOID is a kinase belonging to the AGCVIII family, which regulates the polar distribution of PIN proteins and plays an important role in plant geotropism. However, the origin and evolutionary history of this gene family is not fully known. In this study, we identified 79 similar sequences across 17 plant species genomes (PINOID, D6PK, PINOID2, "hypothetical kinase"). Our results show that the AGCVIII kinase family may have originated from related "Hypothetical Kinases" that come out sister to the rest of the gene family members. These kinases differentiated their functions are found in different plant classes: D6PK in moss and PINOID and PINOID2 evolving in angiosperms including the pioneer plant Amborella trichopoda. Our study investigates the evolution of PINOID kinases from a phylogenetic perspective giving us insight into how this important plant signal transduction network switch evolved to play a fundamental and important function in plant growth and development. We highlight the importance of whole genome duplications and dispersed duplications as opposed to tandem duplications in the evolution of this gene family.

Gene Balance Predicts Transcriptional Responses Immediately Following Ploidy Change in Arabidopsis thaliana.

The gene balance hypothesis postulates that there is selection on gene copy number (gene dosage) to preserve the stoichiometric balance among interacting proteins. This presupposes that gene product abundance is governed by gene dosage and that gene dosage responses are consistent for interacting genes in a dosage-balance-sensitive network or complex. Gene dosage responses, however, have rarely been quantified, and the available data suggest that they are highly variable. We sequenced the transcriptomes of two synthetic autopolyploid accessions of Arabidopsis (Arabidopsis thaliana) and their diploid progenitors, as well as one natural tetraploid and its synthetic diploid produced via haploid induction, to estimate transcriptome size and dosage responses immediately following ploidy change. Similar to what has been observed in previous studies, overall transcriptome size does not exhibit a simple doubling in response to genome doubling, and individual gene dosage responses are highly variable in all three accessions, indicating that expression is not strictly coupled with gene dosage. Nonetheless, putatively dosage balance-sensitive gene groups (Gene Ontology terms, metabolic networks, gene families, and predicted interacting proteins) exhibit smaller and more coordinated dosage responses than do putatively dosage-insensitive gene groups, suggesting that constraints on dosage balance operate immediately following whole-genome duplication and that duplicate gene retention patterns are shaped by selection to preserve dosage balance.

Variation in the Microbiota Associated with Daphnia magna Across Genotypes, Populations, and Temperature.

Studies of how the microbiome varies among individuals, populations, and abiotic conditions are critical for understanding this key component of an organism's biology and ecology. In the case of Daphnia, aquatic microcrustaceans widely used in population/community ecology and environmental science studies, understanding factors that influence microbiome shifts among individuals is useful for both basic and applied research contexts. In this study, we assess differences in the microbiome among genotypes of D. magna collected from three regions along a large latitudinal gradient (Finland, Germany, and Israel). After being reared in the lab for many years, we sought to characterize any differences in genotype- or population-specific microbial communities, and to assess whether the microbiota varied among temperatures. Our study is similar to a recent comparison of the microbial communities among D. magna genotypes raised in different temperatures published by Sullam et al. (Microb Ecol 76(2):506-517, 2017), and as such represents one of the first examples of a reproducible result in microbiome research. Like the previous study, we find evidence for a strong effect of temperature on the microbiome of D. magna, although across a much smaller temperature range representing potential near-future climates. In addition, we find evidence that the microbiomes of D. magna genotypes from different regions are distinct, even years after being brought into the laboratory. Finally, our results highlight a potentially common finding in the expanding area of microbiome research-differences among treatments are not necessarily observed in the most abundant taxonomic groups. This highlights the importance of considering sampling scheme and depth of coverage when characterizing the microbiome, as different experimental designs can significantly impact taxon-specific results, even when large-scale effects are reproduced.

Evolutionary Conflict between Mobile DNA and Host Genomes.

The proportion of eukaryotic genomes composed of active or formerly active mobile elements (MEs) is known to vary widely across lineages, but the explanations for why remain largely unknown. Given that ME activity, like other forms of mutation, is thought to be (on average) slightly deleterious in terms of phenotypic effects, understanding the widespread proliferation of MEs in host genomes requires an evolutionary framework. To better develop such a framework, we review the spectrum of resolutions to the genetic conflict between MEs and their hosts: inactivation of MEs due to mutation accumulation, negative selection (or lack thereof) against hosts with high ME loads, silencing of MEs (by hosts or MEs), ME domestication by their hosts, and the horizontal transfer of MEs to new hosts. We also highlight ecological and evolutionary theory from which ME researchers might borrow in order to explain large-scale patterns of ME dynamics across systems. We hope that a synthesis of the surprisingly significant role played by MEs in the genome, as well as the spectrum of resolutions, applicable theory, and recent discoveries, will have two outcomes for future researchers: better parsing of known variation in ME proliferation patterns across genomes and the development of testable models and predictions regarding the evolutionary trajectory of MEs based on a combination of theory, the comparative method, experimental evolution, and empirical observations.

Employment and paid work among participants in a randomized controlled trial comparing diacetylmorphine and hydromorphone.

BACKGROUND: Employment is one of the less studied but a significant outcome of medication-assisted treatment. Thus, we aimed to explore employment outcomes of medication-assisted treatment with hydromorphone (HDM) or diacetylmorphine (DAM). The secondary aim was to estimate characteristics of this population as well as treatment-related factors associated with these outcomes. METHODS: This was a secondary analysis of a randomized, double blind controlled trial. A total of 102 and 100 participants were randomized to receive injectable DAM or HDM for 6 months respectively. In stage 2, 144 participants were randomized again to receive either oral or injectable forms of the medication they received for another 6 months. Participants were interviewed at 5 timepoints: before and 3, 6, 9 and 12 months after treatment assignment. Generalized estimating equations (GEE) with a logit link was fitted to determine factors related to paid work in the past 30 days. RESULTS: Mean age of participants was 44.3 (SD = 9.6) and 59 (29.2%) participants were men. At each timepoint, 6-8 (3.6%-4.1%) participants reported employment in the past 30 days and 40 to 52 (19.7%-26.7%) reported minimum 1 day of paid work. University or college education [OR = 2.12: 95% CI = (1.25, 3.62), P = 0.01] was significantly associated with paid work after adjustment for age, gender, treatment arms, timepoints, days receiving study treatment, physical health, psychological health and crack cocaine use in the past 30 days. CONCLUSION: The rate of employment was lower among participants of this study compared to similar studies on heroin-assisted treatment. Higher education was associated with increased odds of paid work. A large gap exists between employment rate and the proportion of participants who reported paid work. Supported employment and occupational therapy could optimize the employment outcomes of this population.

Genome-Wide Estimates of Transposable Element Insertion and Deletion Rates in Drosophila Melanogaster.

Knowing the rate at which transposable elements (TEs) insert and delete is critical for understanding their role in genome evolution. We estimated spontaneous rates of insertion and deletion for all known, active TE superfamilies present in a set of Drosophila melanogaster mutation-accumulation (MA) lines using whole genome sequence data. Our results demonstrate that TE insertions far outpace TE deletions in D. melanogaster. We found a significant effect of background genotype on TE activity, with higher rates of insertions in one MA line. We also found significant rate heterogeneity between the chromosomes, with both insertion and deletion rates elevated on the X relative to the autosomes. Further, we identified significant associations between TE activity and chromatin state, and tested for associations between TE activity and other features of the local genomic environment such as TE content, exon content, GC content, and recombination rate. Our results provide the most detailed assessment of TE mobility in any organism to date, and provide a useful benchmark for both addressing theoretical predictions of TE dynamics and for exploring large-scale patterns of TE movement in D. melanogaster and other species.

Expression-level support for gene dosage sensitivity in three Glycine subgenus Glycine polyploids and their diploid progenitors.

Retention or loss of paralogs following duplication correlates strongly with the function of the gene and whether the gene was duplicated by whole-genome duplication (WGD) or by small-scale duplication. Selection on relative gene dosage (to maintain proper stoichiometry among interacting proteins) has been invoked to explain these patterns of duplicate gene retention and loss. In order for gene dosage to be visible to natural selection, there must necessarily be a correlation between gene copy number and gene expression level (transcript abundance), but this has rarely been examined. We used RNA-Seq data from seven Glycine subgenus Glycine species (three recently formed allotetraploids and their four diploid progenitors) to determine if expression patterns and gene dosage responses at the level of transcription are consistent with selection on relative gene dosage. As predicted, metabolic pathways and gene ontologies that are putatively dosage-sensitive based on duplication history exhibited reduced expression variance across species, and more coordinated expression responses to recent WGD, relative to putatively dosage-insensitive networks. We conclude that selection on relative dosage has played an important role in shaping gene networks in Glycine.