Extensive Local Geographic Variation in Locoweed Toxin Produced by a Fungal Endophyte.

Legumes are notorious for coevolutionary arms races where chemical defenses are employed to ward off herbivores-particularly insect seed predators. Locoweeds are legumes containing the toxic alkaloid swainsonine which can poison livestock, but its role as a deterrent for insects is unknown. Swainsonine is produced by the fungal endophyte Alternaria section Undifilum, and the chemical composition of the toxin has been well characterized. Despite this knowledge, the ecological roles and evolutionary drivers of swainsonine toxins in locoweeds remain uncertain. Here, we quantify swainsonine concentrations and herbivory levels in the hyper-diverse locoweed Astragalus lentiginosus to evaluate its role as an evolved chemical defense. We found that A. lentiginosus shows considerable variation in swainsonine concentrations according to variety, in particular showing presence/absence variation at both population and local geographic scales. Surprisingly, herbivory levels from presumed generalist insects emerging from fruits showed no correlation with swainsonine concentrations. Conversely, seed and fruit herbivory levels linked to specialist Acanthoscelides seed beetles increased with concentrations of swainsonine-suggesting a possible coevolutionary arms race. Our results highlight that variation in endophyte-produced toxin systems may not follow classical expectations for geographic variation and ecological roles of plant chemicals. We discuss the implications of these results on plant-endophytic toxin systems and coevolutionary dynamics more broadly, highlighting a considerable need for more research in these systems.

Discordant population structure among rhizobium divided genomes and their legume hosts.

Symbiosis often occurs between partners with distinct life history characteristics and dispersal mechanisms. Many bacterial symbionts have genomes comprising multiple replicons with distinct rates of evolution and horizontal transmission. Such differences might drive differences in population structure between hosts and symbionts and among the elements of the divided genomes of bacterial symbionts. These differences might, in turn, shape the evolution of symbiotic interactions and bacterial evolution. Here we use whole genome resequencing of a hierarchically structured sample of 191 strains of Sinorhizobium meliloti collected from 21 locations in southern Europe to characterize population structures of this bacterial symbiont, which forms a root nodule symbiosis with the host plant Medicago truncatula. S. meliloti genomes showed high local (within-site) variation and little isolation by distance. This was particularly true for the two symbiosis elements, pSymA and pSymB, which have population structures that are similar to each other, but distinct from both the bacterial chromosome and the host plant. Given limited recombination on the chromosome, compared to the symbiosis elements, distinct population structures may result from differences in effective gene flow. Alternatively, positive or purifying selection, with little recombination, may explain distinct geographical patterns at the chromosome. Discordant population structure between hosts and symbionts indicates that geographically and genetically distinct host populations in different parts of the range might interact with genetically similar symbionts, potentially minimizing local specialization.

Combining GWAS and population genomic analyses to characterize coevolution in a legume-rhizobia symbiosis.

The mutualism between legumes and rhizobia is clearly the product of past coevolution. However, the nature of ongoing evolution between these partners is less clear. To characterize the nature of recent coevolution between legumes and rhizobia, we used population genomic analysis to characterize selection on functionally annotated symbiosis genes as well as on symbiosis gene candidates identified through a two-species association analysis. For the association analysis, we inoculated each of 202 accessions of the legume host Medicago truncatula with a community of 88 Sinorhizobia (Ensifer) meliloti strains. Multistrain inoculation, which better reflects the ecological reality of rhizobial selection in nature than single-strain inoculation, allows strains to compete for nodulation opportunities and host resources and for hosts to preferentially form nodules and provide resources to some strains. We found extensive host by symbiont, that is, genotype-by-genotype, effects on rhizobial fitness and some annotated rhizobial genes bear signatures of recent positive selection. However, neither genes responsible for this variation nor annotated host symbiosis genes are enriched for signatures of either positive or balancing selection. This result suggests that stabilizing selection dominates selection acting on symbiotic traits and that variation in these traits is under mutation-selection balance. Consistent with the lack of positive selection acting on host genes, we found that among-host variation in growth was similar whether plants were grown with rhizobia or N-fertilizer, suggesting that the symbiosis may not be a major driver of variation in plant growth in multistrain contexts.

Effects of Domestication on Plant-Microbiome Interactions.

Through the process of domestication, selection is targeted on a limited number of plant traits that are typically associated with yield. As an unintended consequence, domesticated plants often perform poorly compared to their wild progenitors for a multitude of traits that were not under selection during domestication, including abiotic and biotic stress tolerance. Over the past decade, advances in sequencing technology have allowed for the rigorous characterization of host-associated microbial communities, termed the microbiome. It is now clear that nearly every conceivable plant interaction with the environment is mediated by interactions with the microbiome. For this reason, plant-microbiome interactions are an area of great promise for plant breeding and crop improvement. Here, we review the literature to assess the potential impact that domestication has had on plant-microbiome interactions and the current understanding of the genetic basis of microbiome variation to inform plant breeding efforts. Overall, we find limited evidence that domestication impacts the diversity of microbiomes, but domestication is often associated with shifts in the abundance and composition of microbial communities, including taxa of known functional significance. Moreover, genome-wide association studies and mutant analysis have not revealed a consistent set of core candidate genes or genetic pathways that confer variation in microbiomes across systems. However, such studies do implicate a consistent role for plant immunity, root traits, root and leaf exudates and cell wall integrity as key traits that control microbiome colonization and assembly. Therefore, selection on these key traits may pose the most immediate promise for enhancing plant-microbiome interactions through breeding.

Pediatric HIV Case Identification Across 22 PEPFAR-Supported Countries During the COVID-19 Pandemic, October 2019-September 2020.

During 2020, an estimated 150,000 persons aged 0-14 years acquired HIV globally (1). Case identification is the first step to ensure children living with HIV are linked to life-saving treatment, achieve viral suppression, and live long, healthy lives. Successful interventions to optimize pediatric HIV testing during the COVID-19 pandemic are needed to sustain progress toward achieving Joint United Nations Programme on HIV/AIDS (UNAIDS) 95-95-95 targets.* Changes in HIV testing and diagnoses among persons aged 1-14 years (children) were assessed in 22 U.S. President's Emergency Plan for AIDS Relief (PEPFAR)-supported countries during October 1, 2019-September 30, 2020. This period corresponds to the two fiscal quarters before the COVID-19 pandemic (i.e., Q1 and Q2) and the two quarters after the pandemic began (i.e., Q3 and Q4). Testing was disaggregated by age group, testing strategy, and fiscal year quarter. During October 2019-September 2020, PEPFAR supported 4,312,343 HIV tests and identified 74,658 children living with HIV (CLHIV). The number of HIV tests performed was similar during Q1 and Q2, decreased 40.1% from Q2 to Q3, and increased 19.7% from Q3 to Q4. The number of HIV cases identified among children aged 1-14 years (cases identified) increased 7.4% from Q1 to Q2, decreased 29.4% from Q2 to Q3, and increased 3.3% from Q3 to Q4. Although testing in outpatient departments decreased 21% from Q1 to Q4, testing from other strategies increased during the same period, including mobile testing by 38%, facility-based index testing (offering an HIV test to partners and biological children of persons living with HIV) by 8%, and testing children with signs or symptoms of malnutrition within health facilities by 7%. In addition, most tests (61.3%) and cases identified (60.9%) were among children aged 5-14 years (school-aged children), highlighting the need to continue offering HIV testing to older children. These findings provide important information on the most effective strategies for identifying CLHIV during the COVID-19 pandemic. HIV testing programs should continue to use programmatic, surveillance, and financial data at both national and subnational levels to determine the optimal mix of testing strategies to minimize disruptions in pediatric case identification during the COVID-19 pandemic.

Sex Differences in HIV Testing - 20 PEPFAR-Supported Sub-Saharan African Countries, 2019.

Despite progress toward controlling the human immunodeficiency virus (HIV) epidemic, testing gaps remain, particularly among men and young persons in sub-Saharan Africa (1). This observational study used routinely collected programmatic data from 20 African countries reported to the U.S. President's Emergency Plan for AIDS Relief (PEPFAR) from October 2018 to September 2019 to assess HIV testing coverage and case finding among adults (defined as persons aged ≥15 years). Indicators included number of HIV tests conducted, number of HIV-positive test results, and percentage positivity rate. Overall, the majority of countries reported higher HIV case finding among women than among men. However, a slightly higher percentage positivity was recorded among men (4.7%) than among women (4.1%). Provider-initiated counseling and testing (PITC) in health facilities identified approximately two thirds of all new cases, but index testing had the highest percentage positivity in all countries among both sexes. Yields from voluntary counseling and testing (VCT) and mobile testing varied by sex and by country. These findings highlight the need to identify and implement the most efficient strategies for HIV case finding in these countries to close coverage gaps. Strategies might need to be tailored for men who remain underrepresented in the majority of HIV testing programs.

Why are consistently-handed individuals more authoritarian? The role of need for cognitive closure.

Recent studies indicate that individuals with consistent hand preference are more authoritarian than individuals whose preference is relatively inconsistent. We explored the role of epistemic needs in the handedness-authoritarianism relationship. Based on findings that consistent individuals are less cognitively flexible than inconsistent individuals, we hypothesized that consistent-handers would report greater need for definite knowledge. To measure this, we administered the revised Need for Cognitive Closure scale to a sample of undergraduates (N = 235), along with measures of handedness consistency and authoritarian submission. Consistent individuals scored significantly higher on authoritarian submission and need for closure. Need for closure fully mediated the relationship between consistency and submission. Consistent individuals also expressed greater prejudice against authoritarian out-groups such as immigrants and liberals. This effect was partially mediated by authoritarian submission. We theorize that consistent-handers' cognitive inflexibility leads them to covet definite knowledge. These individuals turn to authoritarianism because it promises to stifle dissent and protect existing (conventional) knowledge.

Adenosine receptor expression in the adult zebrafish retina.

Adenosine is an endogenous nucleoside in the central nervous system that acts on adenosine receptors. These are G protein-coupled receptors that have four known subtypes: A1, A2A, A2B, and A3 receptors. In the present study, we aimed to map the location of the adenosine receptor subtypes in adult wild-type zebrafish retina using in situ hybridization and immunohistochemistry. A1R, A2AR, and A2BR mRNA were detected in the ganglion cell layer (GCL), the inner nuclear layer (INL), the outer nuclear layer (ONL), and the outer segment (OS). A3R mRNA was detected in the GCL, ONL, and OS. A1R-immunoreactivity was expressed as puncta in the INL and in the outer plexiform layer (OPL). A1Rs were located within the cone pedicle and contiguous to horizontal cell tips in the OPL. A2AR-immunoreactivity was expressed as puncta in the GCL, inner plexiform layer (IPL), INL, and outer retina. A2AR puncta in the outer retina were situated around the ellipsoids and nuclei of cones, and weakly around the rod nuclei. A1Rs and A2ARs were clustered around ON cone bipolar cell terminals and present in the OFF lamina of the INL but were not expressed on mixed rod/cone response bipolar cell terminals. A2BR-immunoreactivity was mainly localized to the Müller cells, while A3Rs were found to be expressed in retinal ganglion cells of the GCL, INL, ONL, and OS. In summary, all four adenosine receptor subtypes were localized in the zebrafish retina and are in agreement with expression patterns shown in retinas from other species.

Alcohol and Cannabis Use and Sexual Risk Behaviors in the Malawi Defence Force.

Substance abuse is a public health priority in the context of the HIV epidemic, especially in military communities. This cross-sectional study quantified alcohol and cannabis use in the Malawi Defence Force and investigated its associations with condom use, transactional sex, multiple sexual partners, and sexual violence. Participants were 944 male and female service members ≥ 18 years old. Data were collected in 2013 using a computer-assisted self-interview. Twenty-four percent of men and women screened positive for hazardous and harmful drinking [Alcohol Use Disorders Identification Test (AUDIT) score ≥ 8]. About 6% reported using cannabis in the past year and 10% reported using cannabis prior to 1 year ago. Multivariable models found elevated adjusted odds of transactional sex and multiple sexual partners for men with an AUDIT score ≥ 8, and men who reported ever using cannabis. The adjusted odds of experiencing sexual violence were also elevated for men who reported ever using cannabis. These findings add to the growing concern that substance use may perpetuate the HIV epidemic in Sub-Saharan Africa by increasing risky sexual behaviors. A comprehensive military HIV prevention response should include substance use education and appropriate care and treatment for individuals screening positive for hazardous and harmful drinking.

Nitrogen addition does not influence pre-infection partner choice in the legume-rhizobium symbiosis.

PREMISE OF THE STUDY: Resource mutualisms such as the symbiosis between legumes and nitrogen-fixing rhizobia are context dependent and are sensitive to various aspects of the environment, including nitrogen (N) addition. Mutualist hosts such as legumes are also thought to use mechanisms such as partner choice to discriminate among potential symbionts that vary in partner quality (fitness benefits conferred to hosts) and thus impose selection on rhizobium populations. Together, context dependency and partner choice might help explain why the legume-rhizobium mutualism responds evolutionarily to N addition, since plant-mediated selection that shifts in response to N might be expected to favor different rhizobium strains in different N environments. METHODS: We test for the influence of context dependency on partner choice in the model legume, Medicago truncatula, using a factorial experiments with three plant families across three N levels with a mixed inoculation of three rhizobia strains. KEY RESULTS: Neither the relative frequencies of rhizobium strains occupying host nodules, nor the size of those nodules, differed in response to N level. CONCLUSIONS: Despite the lack of context dependence, plant genotypes respond very differently to mixed populations of rhizobia, suggesting that these traits are genetically variable and thus could evolve in response to longer-term increases in N.

Sexually transmitted infections and sexual behaviour of deploying shipboard US military personnel: a cross-sectional analysis.

OBJECTIVES: Sexually transmitted infection (STI) prevalence and risk behaviour may differ at different phases of deployment. We examined STI prevalence and sexual behaviour in the predeployment time period (12 months prior) among recently deployed shipboard US Navy and Marine Corps military personnel. METHODS: Data were collected from 1938 male and 515 female service members through an anonymous, self-completed survey assessing sexual behaviours and STI acquisition characteristics in the past 12 months. Cross-sectional sex-stratified descriptive statistics are reported. RESULTS: Overall, 67% (n=1262/1896) reported last sex with a military beneficiary (spouse, n=931, non-spouse service member, n=331). Among those with a sexual partner outside their primary partnership, 24% (n=90/373) reported using a condom the last time they had sex and 30% (n=72/243) reported their outside partner was a service member. In total, 90% (n=210/233) reported acquiring their most recent STI in the USA (88%, n=126/143 among those reporting ≥1 deployments and an STI ≥1 year ago) and a significantly higher proportion (p<0.01) of women than men acquired the STI from their regular partner (54% vs 21%) and/or a service member (50% vs 26%). CONCLUSIONS: Findings suggest a complex sexual network among service members and military beneficiaries. Findings may extend to other mobile civilian and military populations. Data suggest most STI transmission within the shipboard community may occur in local versus foreign ports but analyses from later time points in deployment are needed. These data may inform more effective STI prevention interventions.

Consistent-handed individuals are more authoritarian.

Individuals differ in the consistency with which they use one hand over the other to perform everyday activities. Some individuals are very consistent, habitually using a single hand to perform most tasks. Others are relatively inconsistent, and hence make greater use of both hands. More- versus less-consistent individuals have been shown to differ in numerous aspects of personality and cognition. In several respects consistent-handed individuals resemble authoritarian individuals. For example, both consistent-handedness and authoritarianism have been linked to cognitive inflexibility. Therefore we hypothesised that consistent-handedness is an external marker for authoritarianism. Confirming our hypothesis, we found that consistent-handers scored higher than inconsistent-handers on a measure of submission to authority, were more likely to identify with a conservative political party (Republican), and expressed less-positive attitudes towards out-groups. We propose that authoritarianism may be influenced by the degree of interaction between the left and right brain hemispheres, which has been found to differ between consistent- and inconsistent-handed individuals.

Conventional management has a greater negative impact on Phaseolus vulgaris L. rhizobia diversity and abundance than water scarcity.

Introduction: Drought is one of the biggest problems for crop production and also affects the survival and persistence of soil rhizobia, which limits the establishment of efficient symbiosis and endangers the productivity of legumes, the main source of plant protein worldwide. Aim: Since the biodiversity can be altered by several factors including abiotic stresses or cultural practices, the objective of this research was to evaluate the effect of water availability, plant genotype and agricultural management on the presence, nodulation capacity and genotypic diversity of rhizobia. Method: A field experiment was conducted with twelve common bean genotypes under irrigation and rain-fed conditions, both in conventional and organic management. Estimation of the number of viable rhizobia present in soils was performed before the crop establishment, whereas the crop yield, nodule number and the strain diversity of bacteria present in nodules were determined at postharvest. Results: Rainfed conditions reduced the number of nodules and of isolated bacteria and their genetic diversity, although to a lesser extent than the agrochemical inputs related to conventional management. In addition, the effect of water scarcity on the conventional management soil was greater than observed under organic conditions. Conclusions: The preservation of diversity will be a key factor to maintain crop production in the future, as problems caused by drought will be exacerbated by climate change and organic management can help to maintain the biodiversity of soil microbiota, a fundamental aspect for soil health and quality.

Development of Allosteric Small Molecule APOBEC3B Inhibitors from In Silico Screening.

APOBEC3B cytosine deaminase contributes to the mutational burdens of tumors, resulting in tumor progression and therapy resistance. Small molecule APOBEC3B inhibitors have potential to slow or mitigate these detrimental outcomes. Through molecular dynamics (MD) simulations and computational solvent mapping analysis, we identified a novel putative allosteric pocket on the C-terminal domain of APOBEC3B (A3Bctd), and virtually screened the ChemBridge Diversity Set (N~110,000) against both the active and potential allosteric sites. Selected high-scoring compounds were subsequently purchased, characterized for purity and composition, and tested in biochemical assays, which yielded 13 hit compounds. Orthogonal NMR assays verified binding to the target protein. Initial selectivity studies suggest these compounds preferentially target A3Bctd over related deaminase APOBEC3A (A3A), and MD simulations indicate this selectivity may be due to the steric repulsion from H56 that is unique to A3A. Taken together, our studies represent the first virtual screening effort against A3Bctd that has yielded candidate inhibitors suitable for further development.

Genetic architecture of flowering time differentiation between locally adapted populations of Arabidopsis thaliana.

To gain an understanding of the genetic basis of adaptation, we conducted quantitative trait locus (QTL) mapping for flowering time variation between two winter annual populations of Arabidopsis thaliana that are locally adapted and display distinct flowering times. QTL mapping was performed with large (n = 384) F(2) populations with and without vernalization, in order to reveal both the genetic basis of a vernalization requirement and that of variation in flowering time given vernalization. In the nonvernalization treatment, none of the Sweden parents flowered, whereas all of the Italy parents and 42% of the F(2)s flowered. We identified three QTLs for flowering without vernalization, with much of the variation being attributed to a QTL co-localizing with FLOWERING LOCUS C (FLC). In the vernalization treatment, all parents and F(2)s flowered, and six QTLs of small to moderate effect were revealed, with underlying candidate genes that are members of the vernalization pathway. We found no evidence for a role of FRIGIDA in the regulation of flowering times. These results contribute to a growing body of evidence aimed at the identification of ecologically relevant genetic variation for flowering time in Arabidopsis, and set the stage for functional studies to determine the link between flowering time loci and fitness.

Prevalence of PTSD and depression, and associated sexual risk factors, among male Rwanda Defense Forces military personnel.

OBJECTIVES: To assess depression and PTSD prevalence among the Rwanda Defense Forces (RDF) and evaluate whether sexual risk behaviour, STIs, HIV and alcohol use were significantly higher among those who screened positive. METHODS: Consenting active-duty male RDF personnel, aged ≥21 years, completed an anonymous sexual risk survey linked to HIV rapid testing that included standardised assessments for PTSD (PCL-M), depression (CES-D) and alcohol use (AUDIT). PTSD and depression prevalence were calculated (data available for 1238 and 1120 participants, respectively), and multivariable regression analyses were conducted. RESULTS: 22.5% screened positive for depression, 4.2% for PTSD and 3.4% for both. In adjusted analyses, odds of either depression or PTSD were significantly higher in participants reporting STI symptoms (OR = 2.27, 2.78, respectively) and harmful alcohol use (OR = 3.13, 3.21, respectively). Sex with a high-risk sex partner, lower rank and never deploying were also significantly associated with depression in adjusted analyses. CONCLUSIONS: Nearly one-fourth of RDF participants screened positive for PTSD or depression, which impacts sexual risk behaviour, HIV acquisition risk and military readiness. Findings may extend to other deploying militaries and provide additional evidence of an association between mental health status and sexual risk behaviour. Effective mental health treatment interventions that also include alcohol use assessments, STI identification/treatment and sexual risk behaviour reduction are needed.

HIV seroprevalence, associated risk behavior, and alcohol use among male Rwanda Defense Forces military personnel.

A cross-sectional study was conducted among active-duty male soldiers, aged ≥21 years, in the Rwanda Defense Forces (RDF) and included an anonymous behavioral survey and HIV rapid testing to determine risk factors associated with HIV seroprevalence. Overall prevalence was 2.6 % (95 % CI: 1.84-3.66); personnel who were divorced, separated or widowed, served ≥6 years, never deployed, uncircumcised, reported STI symptoms, had ≥6 lifetime sex partners, or screened positive for harmful alcohol use (via Alcohol Use Disorders Identification Test) had higher HIV prevalence. Ever being divorced, separated or widowed (OR = 29.8; 95 % CI: 5.5-159.9), and STI symptoms (OR = 3.4; 95 % CI: 1.5-7.6) were significantly associated with infection, after multivariable adjustment, while circumcision was protective (OR = 0.4; 95 % CI: 0.2-0.9). Despite mobility and other factors that uniquely influence HIV transmission in militaries, RDF prevalence was similar to the general population. A reason for this finding may be conservative sexual behavior combined with effective leadership-supported prevention programs. Data suggest a concentrated rather than generalized epidemic, with targets identified for intervention.

Development of Allosteric NIK Ligands from Fragment-Based NMR Screening.

NF-κB inducing kinase (NIK) is vital for the induction of many immune responses, and as such, NIK dysregulation has been implicated in various inflammatory diseases and cancers. NIK has been pursued as a potential therapeutic target, and small-molecule inhibitors that bind the orthosteric site on NIK have been reported. However, despite the established chemical matter, NIK inhibitors have not yet reached the clinic. With the goal of developing allosteric NIK ligands using a fragment-based NMR screening approach, we report the identification and development of a series of allosteric, fragment-sized NIK ligands that bind with micromolar potency and good ligand efficiency.

Considerations to Improve Pediatric HIV Testing and Close the Treatment Gap in 16 African Countries.

BACKGROUND: In 2019, South Africa, Nigeria, Tanzania, Democratic Republic of Congo, Uganda, Mozambique, Zambia, Angola, Cameroon, Zimbabwe, Ghana, Ethiopia, Malawi, Kenya, South Sudan and Côte d'Ivoire accounted for 80% of children living with HIV (CLHIV) not receiving HIV treatment. This manuscript describes pediatric HIV testing to inform case-finding strategies. METHODS: We analyzed US President's Emergency Plan for AIDS Relief monitoring, evaluation, and reporting data (October 1, 2018 to September 30, 2019) for these 16 countries. Number of HIV tests and positive results were reported by age band, country, treatment coverage and testing modality. The number needed to test (NNT) to identify 1 new CLHIV 1-14 years was measured by testing modality and country. The pediatric testing gap was estimated by multiplying the estimated number of CLHIV unaware of their status by NNT per country. RESULTS: Among children, 6,961,225 HIV tests were conducted, and 101,762 CLHIV were identified (NNT 68), meeting 17.6% of the pediatric testing need. Index testing accounted for 13.0% of HIV tests (29.7% of positive results, NNT 30), provider-initiated testing and counseling 65.9% of tests (43.6% of positives, NNT 103), and universal testing at sick entry points 5.3% of tests (6.5% of positives, NNT 58). CONCLUSIONS: As countries near HIV epidemic control for adults, the need to increase pediatric testing continues. Each testing modality - PITC, universal testing at sick entry points, and index testing - offers unique benefits. These results illustrate the comparative advantages of including a strategic mix of testing modalities in national programs to increase pediatric HIV case finding.

Rapid Synthesis of Cryo-ET Data for Training Deep Learning Models.

Deep learning excels at cryo-tomographic image restoration and segmentation tasks but is hindered by a lack of training data. Here we introduce cryo-TomoSim (CTS), a MATLAB-based software package that builds coarse-grained models of macromolecular complexes embedded in vitreous ice and then simulates transmitted electron tilt series for tomographic reconstruction. We then demonstrate the effectiveness of these simulated datasets in training different deep learning models for use on real cryotomographic reconstructions. Computer-generated ground truth datasets provide the means for training models with voxel-level precision, allowing for unprecedented denoising and precise molecular segmentation of datasets. By modeling phenomena such as a three-dimensional contrast transfer function, probabilistic detection events, and radiation-induced damage, the simulated cryo-electron tomograms can cover a large range of imaging content and conditions to optimize training sets. When paired with small amounts of training data from real tomograms, networks become incredibly accurate at segmenting in situ macromolecular assemblies across a wide range of biological contexts.