Selective Pressure Research Articles

Horizontal gene transfer plays a crucial role in the development of antibiotic resistance in an antibiotic-free shrimp farming system

Antibiotic selective pressure in aquaculture systems often results in the antibiotic resistance genes (ARGs) proliferation. Nonetheless, a paucity of data exists concerning the mechanisms of ARGs development in aquaculture systems without the influences of antibiotics. This study utilized metagenomic approaches to elucidate the dynamics and transfer mechanisms of ARGs throughout the aquaculture of Pacific white shrimp. A marked change in the resistome was observed throughout the aquaculture without antibiotics. The total ARGs relative abundance increased from 0.05 to 0.33 by day 90 of cultivation, with even higher in mixed wastewater (0.44). Both bacterial communities and mobile genetic elements play pivotal roles in the development of ARGs. Metagenome-assembled genomes showed enrichment of environmentally intrinsic ARGs on chromosomes including macB and mdtK. The plasmid-mediated horizontal transfer was recognized as a principal factor contributing to the rise of ARGs, particularly for tetG and floR, and this led to an escalation of resistance risk, peaking at a risks core of 35.43 on day 90. This study demonstrates that horizontal gene transfer plays a crucial role in ARGs development without antibiotic pressure, which can provide a theoretical foundation for controlling ARGs proliferation in aquaculture systems. Environmental ImplicationGiven the excessive use of antibiotics, antibiotic resistance genes (ARGs) are emerging as a new form of hazardous pollutant. Previous studies have indicated that incorporating antibiotics in aquaculture can result in the accumulation of ARGs. In contrast, this study examines an aquaculture system unaffected by antibiotics, expressly exploring the impact of horizontal gene transfer on the accumulation and risk propagation of ARGs during the aquaculture process, aiming to provide a theoretical reference for the control of ARGs in the aquaculture industry.

Evolution: Decoding the adaptation of multi-eyed visual systems

Many invertebrates possess more than two pairs of eyes- but does eye redundancy aid in ecological diversification? A new study finds varied size adaptation of different eye pairs in spiders, demonstrating how developmental modularity of multi-eyed systems effectively balances selective pressures.

Composition of soil Frankia assemblages across ecological drivers parallels that of nodule assemblages in Alnus incana ssp. tenuifolia in interior Alaska.

In root nodule symbioses (RNS) between nitrogen (N)-fixing bacteria and plants, bacterial symbionts cycle between nodule-inhabiting and soil-inhabiting niches that exert differential selection pressures on bacterial traits. Little is known about how the resulting evolutionary tension between host plants and symbiotic bacteria structures naturally occurring bacterial assemblages in soils. We used DNA cloning to examine soil-dwelling assemblages of the actinorhizal symbiont Frankia in sites with long-term stable assemblages in Alnus incana ssp. tenuifolia nodules. We compared: (1) phylogenetic diversity of Frankia in soil versus nodules, (2) change in Frankia assemblages in soil versus nodules in response to environmental variation: both across succession, and in response to long-term fertilization with N and phosphorus, and (3) soil assemblages in the presence and absence of host plants. Phylogenetic diversity was much greater in soil-dwelling than nodule-dwelling assemblages and fell into two large clades not previously observed. The presence of host plants was associated with enhanced representation of genotypes specific to A. tenuifolia, and decreased representation of genotypes specific to a second Alnus species. The relative proportion of symbiotic sequence groups across a primary chronosequence was similar in both soil and nodule assemblages. Contrary to expectations, both N and P enhanced symbiotic genotypes relative to non-symbiotic ones. Our results provide a rare set of field observations against which predictions from theoretical and experimental work in the evolutionary ecology of RNS can be compared.

Tebuconazole exacerbates co-occurrence and horizontal transfer of antibiotic resistance genes

As one of the most widely used pesticides in the global fungicide market, tebuconazole has become heavily embedded in soil along with antibiotic resistance genes (ARGs). However, it remains unclear whether the selective pressure produced by tebuconazole affects ARGs and their horizontal transfer. In this experiment, we simulated a tebuconazole-contaminated soil ecosystem and observed changes in the abundance of ARGs and mobile genetic element (MGEs) due to tebuconazole exposure. We also established a plasmid RP4-mediated conjugative transfer system to investigate in depth the impact of tebuconazole on the horizontal transfer of ARGs and its mechanism of action. The results showed that under tebuconazole treatment at concentrations ranging from 0 to 10 mg/L, there was a gradual increase in the frequency of plasmid conjugative transfer, peaking at 10 mg/L which was 7.93 times higher than that of the control group, significantly promoting horizontal transfer of ARGs. Further analysis revealed that the conjugative transfer system under tebuconazole stress exhibited strong ability to form biofilm, and the conjugative transfer frequency ratio of biofilm to planktonic bacteria varied with the growth cycle of biofilm. Additionally, scanning electron microscopy and flow cytometry demonstrated increased cell membrane permeability in both donor and recipient bacteria under tebuconazole stress, accompanied by upregulation of ompA gene expression controlling cell membrane permeability. Furthermore, enzyme activity assays indicated significant increases in CAT, SOD activity, and GSH content in recipient bacteria under tebuconazole stress. Moreover, expression levels of transmembrane transporter gene trfAp as well as genes involved in oxidative stress and SOS response were found to be correlated with the frequency of plasmid conjugative transfer.

Single-nucleotide polymorphisms and copy number variations drive adaptive evolution to freezing stress in a subtropical evergreen broad-leaved tree: hexaploid wild Camellia oleifera

Subtropical evergreen broad-leaved trees are usually vulnerable to freezing stress, while hexaploid wild Camellia oleifera shows strong freezing tolerance. As a valuable genetic resource of woody oil crop C. oleifera, wild C. oleifera can serve as a case for studying the molecular bases of adaptive evolution to freezing stress. Here, 47 wild C. oleifera from 11 natural distribution sites in China and 4 relative species of C. oleifera were selected for genome sequencing. “Min Temperature of Coldest Month” (BIO6) had the highest comprehensive contribution to wild C. oleifera distribution. The population genetic structure of wild C. oleifera could be divided into two groups: in cold winter (BIO6 ≤ 0°C) and warm winter (BIO6 > 0°C) areas. Wild C. oleifera in cold winter areas might have experienced stronger selection pressures and population bottlenecks with lower Ne than those in warm winter areas. 155 single-nucleotide polymorphisms (SNPs) were significantly correlated with the key bioclimatic variables (106 SNPs significantly correlated with BIO6). Twenty key SNPs and 15 key copy number variation regions (CNVRs) were found with genotype differentiation >50% between the two groups of wild C. oleifera. Key SNPs in cis-regulatory elements might affect the expression of key genes associated with freezing tolerance, and they were also found within a CNVR suggesting interactions between them. Some key CNVRs in the exon regions were closely related to the differentially expressed genes under freezing stress. The findings suggest that rich SNPs and CNVRs in polyploid trees may contribute to the adaptive evolution to freezing stress.

Interplay among manures, vegetable types, and tetracycline resistance genes in rhizosphere microbiome.

The rapid global emergence of antibiotic resistance genes (ARGs) is a substantial public health concern. Livestock manure serves as a key reservoir for tetracycline resistance genes (TRGs), serving as a means of their transmission to soil and vegetables upon utilization as a fertilizer, consequently posing a risk to human health. The dynamics and transfer of TRGs among microorganisms in vegetables and fauna are being investigated. However, the impact of different vegetable species on acquisition of TRGs from various manure sources remains unclear. This study investigated the rhizospheres of three vegetables (carrots, tomatoes, and cucumbers) grown with chicken, sheep, and pig manure to assess TRGs and bacterial community compositions via qPCR and high-throughput sequencing techniques. Our findings revealed that tomatoes exhibited the highest accumulation of TRGs, followed by cucumbers and carrots. Pig manure resulted in the highest TRG levels, compared to chicken and sheep manure, in that order. Bacterial community analyses revealed distinct effects of manure sources and the selective behavior of individual vegetable species in shaping bacterial communities, explaining 12.2% of TRG variation. Firmicutes had a positive correlation with most TRGs and the intl1 gene among the dominant phyla. Notably, both the types of vegetables and manures significantly influenced the abundance of the intl1 gene and soil properties, exhibiting strong correlations with TRGs and elucidating 30% and 17.7% of TRG variance, respectively. Our study delineated vegetables accumulating TRGs from manure-amended soils, resulting in significant risk to human health. Moreover, we elucidated the pivotal roles of bacterial communities, soil characteristics, and the intl1 gene in TRG fate and dissemination. These insights emphasize the need for integrated strategies to reduce selection pressure and disrupt TRG transmission routes, ultimately curbing the transmission of tetracycline resistance genes to vegetables.

Impact of abiotic stressors on nutrient removal and rhizomicrobiome composition in floating treatment wetland with Equisetum hyemale

Floating treatment wetlands (FTW) are receiving growing interest as a phyto-technology. However, there are significant research gaps regarding the actual role of plant species and plant-microbiome interactions. In this study, the nutrient uptake of Equisetum hyemale was examined in FTW microcosms under the influence of abiotic stressors: As (3 mg/L) and Pb (3 mg/L) as well as Cl− (300 and 800 mg/L) in reference to a control during a short screening experiment. High removal efficiency of nutrients in water solutions, up to 88 % for TN and 93 % for PO4-P, was observed. However, PO4-P removal was inhibited in the As reactor, with a maximum efficiency of only 11 %. Lead and As were removed with high efficiency, reaching 98 % and 79 % respectively. At the same time only Pb was effectively bound to root biomass, reaching up to 51 %. Limited As accumulation of 0.5 % in plant roots suggests that microbial processes play a major role in its reduction. The development and structure of microbiome in the microcosms was analysed by means of 16S rRNA gene amplicon sequencing, proving that Pb was the most influential factor in terms of selection pressure on specified bacterial groups. In the As treatment, the emergence of a Serratia subpopulation was observed, while the Cl− treatment preserved a rhizobiome composition most closely resembling the control. This study indicates that E. hyemale is a suitable species for use in FTWs treating Pb polluted water that at the same time is capable to withstand periodic increases in salinity. E. hyemale exhibits low As binding in biomass; however, extended exposure might amplify this effect because of the slow-acting, but beneficial, mechanism of As uptake by roots and shoots. Microbiome analysis complements insights into mechanisms of FTW performance and impact of stress factors on bacterial structure and functions.

Designed De Novo α-Sheet Peptides Destabilize Bacterial Biofilms and Increase the Susceptibility of E. coli and S. aureus to Antibiotics.

Biofilm-associated microbes are 10-1000 times less susceptible to antibiotics. An emerging treatment strategy is to target the structural components of biofilm to weaken the extracellular matrix without introducing selective pressure. Biofilm-associated bacteria, including Escherichia coli and Staphylococcus aureus, generate amyloid fibrils to reinforce their extracellular matrix. Previously, de novo synthetic α-sheet peptides designed in silico were shown to inhibit amyloid formation in multiple bacterial species, leading to the destabilization of their biofilms. Here, we investigated the impact of inhibiting amyloid formation on antibiotic susceptibility. We hypothesized that combined administration of antibiotics and α-sheet peptides would destabilize biofilm formation and increase antibiotic susceptibility. Two α-sheet peptides, AP90 and AP401, with the same sequence but inverse chirality at every amino acid were tested: AP90 is L-amino acid dominant while AP401 is D-amino acid dominant. For E. coli, both peptides increased antibiotic susceptibility and decreased the biofilm colony forming units when administered with five different antibiotics, and AP401 caused a greater increase in all cases. For S. aureus, increased biofilm antibiotic susceptibility was also observed for both peptides, but AP90 outperformed AP401. A comparison of the peptide effects demonstrates how chirality influences biofilm targeting of gram-negative E. coli and gram-positive S. aureus. The observed increase in antibiotic susceptibility highlights the role amyloid fibrils play in the reduced susceptibility of bacterial biofilms to specific antibiotics. Thus, the co-administration of α-sheet peptides and existing antibiotics represents a promising strategy for the treatment of biofilm infections.

Frequency-dependent selection of neoantigens fosters tumor immune escape and predicts immunotherapy response

Cancer is an evolutionary process shaped by selective pressure from the microenvironments. However, recent studies reveal that certain tumors undergo neutral evolution where there is no detectable fitness difference amongst the cells following malignant transformation. Here, through computational modeling, we demonstrate that negative frequency-dependent selection (or NFDS), where the immune response against cancer cells depends on the clonality of neoantigens, can lead to an immunogenic landscape that is highly similar to neutral evolution. Crucially, NFDS promotes high antigenic heterogeneity and early immune evasion in hypermutable tumors, leading to poor responses to immune checkpoint blockade (ICB) therapy. Our model also reveals that NFDS is characterized by a negative association between average clonality and total burden of neoantigens. Indeed, this unique feature of NFDS is common in the whole-exome sequencing (WES) datasets (357 tumor samples from 275 patients) from four melanoma cohorts with ICB therapy and a non-small cell lung cancer (NSCLC) WES dataset (327 tumor samples from 100 patients). Altogether, our study provides quantitative evidence supporting the theory of NFDS in cancer, explaining the high prevalence of neutral-looking tumors. These findings also highlight the critical role of frequency-dependent selection in devising more efficient and predictive immunotherapies.

Habitat quality or quantity? Niche marginality across 21 plants and animals suggests differential responses between highland and lowland species to past climatic changes

Climatic changes can affect species distributions, population abundance, and evolution. Such organismal responses could be determined by the amount and quality of available habitats, which can vary independently. In this study, we assessed changes in habitat quantity and quality independently to generate explicit predictions of the species' responses to climatic changes between Last Glacial Maximum (LGM) and present day. We built ecological niche models for genetic groups within 21 reptile, mammal, and plant taxa from the Baja California peninsula inhabiting lowland or highland environments. Significant niche divergence was detected for all clades within species, along with significant differences in the niche breadth and area of distribution between northern and southern clades. We quantified habitat quantity from the distribution models, and most clades showed a reduction in distribution area towards LGM. Further, niche marginality (used as a measure of habitat quality) was higher during LGM for most clades, except for northern highland species. Our results suggest that changes in habitat quantity and quality can affect organismal responses independently. This allows the prediction of genomic signatures associated with changes in effective population size and selection pressure that could be explicitly tested from our models.

Cellular interactions and evolutionary origins of endosymbiotic relationships with ciliates.

As unicellular predators, ciliates engage in close associations with diverse microbes, laying the foundation for the establishment of endosymbiosis. Originally heterotrophic, ciliates demonstrate the ability to acquire phototrophy by phagocytizing unicellular algae or by sequestering algal plastids. This adaptation enables them to gain photosynthate and develop resistance to unfavorable environmental conditions. The integration of acquired phototrophy with intrinsic phagotrophy results in a trophic mode known as mixotrophy. Additionally, ciliates can harbor thousands of bacteria in various intracellular regions, including the cytoplasm and nucleus, exhibiting species specificity. Under prolonged and specific selective pressure within hosts, bacterial endosymbionts evolve unique lifestyles and undergo particular reductions in metabolic activities. Investigating the research advancements in various endosymbiotic cases within ciliates will contribute to elucidate patterns in cellular interaction and unravel the evolutionary origins of complex traits.

The evolution of mammalian Rem2: unraveling the impact of purifying selection and coevolution on protein function, and implications for human disorders.

Rad And Gem-Like GTP-Binding Protein 2 (Rem2), a member of the RGK family of Ras-like GTPases, is implicated in Huntington's disease and Long QT Syndrome and is highly expressed in the brain and endocrine cells. We examine the evolutionary history of Rem2 identified in various mammalian species, focusing on the role of purifying selection and coevolution in shaping its sequence and protein structural constraints. Our analysis of Rem2 sequences across 175 mammalian species found evidence for strong purifying selection in 70% of non-invariant codon sites which is characteristic of essential proteins that play critical roles in biological processes and is consistent with Rem2's role in the regulation of neuronal development and function. We inferred epistatic effects in 50 pairs of codon sites in Rem2, some of which are predicted to have deleterious effects on human health. Additionally, we reconstructed the ancestral evolutionary history of mammalian Rem2 using protein structure prediction of extinct and extant sequences which revealed the dynamics of how substitutions that change the gene sequence of Rem2 can impact protein structure in variable regions while maintaining core functional mechanisms. By understanding the selective pressures, protein- and gene - interactions that have shaped the sequence and structure of the Rem2 protein, we gain a stronger understanding of its biological and functional constraints.

Selection of Saccharum spp. × Saccharum spontaneum progeny for sugar and biomass traits

ABSTRACT This study evaluated an interspecific hybrid (Saccharum spp. × S. spontaneum) population with the aim of developing germplasm for use in both sugar and bioenergy (biomass) production. Specific objectives were to determine the genetic variability and heritability among the interspecific hybrid progenies for traits of economic importance and to use the Best Linear Unbiased Predictions (BLUPs) to determine their genotypic values. The 46 interspecific hybrids used in this study originated from crossing commercial sugarcane cultivars (UT5, F152, and KK07–559) as female and S. spontaneum clones (THS98–41, THS98–91, THS98–95, THS98–94, and THS97–51) as male parents. There were significant residual variances, attributed to the small plot size, but the juice quality traits were measured with relatively higher precision than other traits. Selection recommendations varied for different traits, suggesting selection pressure could be moderate to high for juice quality traits and moderate for yield-related traits. No hybrid genotypes were found to outperform cultivar parents for traits such as commercial cane sugar and low fiber, necessitating further germplasm enhancement for improvement of varieties destined for sugar production. On the contrary, transgressive segregation was observed for cane yield and other traits influencing biomass yield. The production potential of these hybrids could be tested in larger plots across multiple locations.

Lactase persistence in the Jordanian population: Potential effects of the Arabian Peninsula and Sahara's aridification

The single nucleotide polymorphism (SNP) −13910 C > T has proved a good predictor of the incidence of lactase persistence in Europe and South Asia. Yet, this is not the case in the Near East, although this region is a passageway between the two continents. Lactase persistence is associated with cattle breeding, which originated in the Fertile Crescent of the Near East and spread later during the Middle Neolithic throughout Europe. Here we analyzed five SNPs (−13915 T > G (rs41380347), −13910 C > T (rs4988235), −13907 C > G (rs41525747), −14009 T > G (rs869051967), and −14010 G > C (rs145946881)) in three Jordanian human groups, namely the Bedouins, Jordan valley farmers, and Jordanian urban people. The SNPs −14009 T > G and −14010 G > C were not detected in the sample, −13907 C > G was virtually non-existent, −13910 C > T showed low frequencies, and −13915 T > G exhibited salient frequencies. The estimated incidence of lactase persistence was lower in the urban population (16 %), intermediate in the Jordan Valley's farmer population (30 %), and higher among the Bedouins (62 %). In explaining our findings, we postulated climatic change brought about by the aridification episode of the Arabian Peninsula and the Sahara 4200 years ago. This climatic milestone caused the collapse of the Akkadian Empire and the Old Kingdom in Egypt. Also, it could have led to a drastic decline of cattle in the region, being replaced by the domestication of camels. Loss of traditional crops and increasing dependence on camel milk might have triggered local selective pressures, mainly associated with −13915 T > G and differentiated from the ones in Europe, associated with −13910 C > T.

Medullary Thyroid Cancer: Molecular Drivers and Immune Cellular Milieu of the Tumour Microenvironment-Implications for Systemic Treatment.

In this review, we explore the underlying molecular biology of medullary thyroid carcinoma (MTC) and its interplay with the host immune system. MTC is consistently driven by a small number of specific pathogenic variants, beyond which few additional genetic events are required for tumorigenesis. This explains the exceedingly low tumour mutational burden seen in most MTC, in contrast to other cancers. However, because of the low tumour mutational burden (TMB), there is a correspondingly low level of tumour-associated neoantigens that are presented to the host immune system. This reduces tumour visibility and vigour of the anti-tumour immune response and suggests the efficacy of immunotherapy in MTC is likely to be poor, acknowledging this inference is largely based on the extrapolation of data from other tumour types. The dominance of specific RET (REarranged during Transfection) pathogenic variants in MTC tumorigenesis rationalizes the observed efficacy of the targeted RET-specific tyrosine kinase inhibitors (TKIs) in comparison to multi-kinase inhibitors (MKIs). Therapeutic durability of pathway inhibitors is an ongoing research focus. It may be limited by the selection pressure TKI treatment creates, promoting survival of resistant tumour cell clones that can escape pathway inhibition through binding-site mutations, activation of alternate pathways, and modulation of the cellular and cytokine milieu of the tumour microenvironment (TME).

Gill morphology adapted to oxygen-limited caves in Astyanax mexicanus.

Sensing and acquiring dissolved oxygen is crucial for nearly all aquatic life. This may become even more vital as dissolved oxygen concentrations continue to decline in many aquatic environments. While certain phenotypes that enable fish to live in low oxygen have been characterized, adaptations that arise following sudden, drastic reductions in dissolved oxygen are relatively unknown. Here, we assessed the blind Mexican cavefish, Astyanax mexicanus, for alterations to gill morphology that may be adaptive for life in hypoxic caves. The Astyanax system provides the unique opportunity to compare gill morphology between stereotypical "surface" adapted morphotypes and obligate cave-dwelling conspecifics. While the surface environment is well-oxygenated, cavefish must cope with significantly reduced oxygen. We began by quantifying traditional morphological gill traits including filament number and length as well as lamellar density and height in surface fish and two distinct cave populations, Pachón and Tinaja. This enabled us to estimate total lamellar height, a proxy for gill surface area. We then used immunohistochemical staining to label 5-HT-positive neuroepithelial cells (NECs), which serve as key oxygen sensors in fish. We discovered an increase in gill surface area for both cavefish populations compared to surface, which may enable a higher capacity of oxygen acquisition. Additionally, we found more NECs in Pachón cavefish compared to both surface fish and Tinaja cavefish, suggesting certain selective pressures may be cave-specific. Collectively, this work provides evidence that cavefish have adapted to low oxygen conditions via alterations to gill morphology and oxygen sensing, and informs evolutionary mechanisms of rapid adaptation to dramatic, chronic hypoxia.

Ecological disturbance alters the adaptive benefits of social ties.

Extreme weather events radically alter ecosystems. When ecological damage persists, selective pressures on individuals can change, leading to phenotypic adjustments. For group-living animals, social relationships may be a mechanism enabling adaptation to ecosystem disturbance. Yet whether such events alter selection on sociality and whether group-living animals can, as a result, adaptively change their social relationships remain untested. We leveraged 10 years of data collected on rhesus macaques before and after a category 4 hurricane caused persistent deforestation, exacerbating monkeys' exposure to intense heat. In response, macaques demonstrated persistently increased tolerance and decreased aggression toward other monkeys, facilitating access to scarce shade critical for thermoregulation. Social tolerance predicted individual survival after the hurricane, but not before it, revealing a shift in the adaptive function of sociality.

Comparative genomic analysis of Brazilian Mesomycoplasma ovipneumoniae strains revealed genomic differences associated with the geographic origin and health status and mutations in the gyrA

Sheep respiratory disease (SRD) is a multifactorial illness commonly affecting sheep. Mesomycoplasma (Mycoplasma) ovipneumoniae is one of the most important etiological agents of SRD and should be better understood, especially in countries where it was recently detected, such as Brazil. Also, the intensive use of quinolones in mycoplasmal infections increases the selective pressure for resistance to this drug class, and no data about antimicrobial resistance in Brazil is available. Therefore, this study aimed to perform a comparative genomic analysis of newly isolated Brazilian M. ovipneumoniae strains, identify point mutations in target genes that may be associated with antibiotic resistance, and perform a phylogenomic analysis of these strains with available genome representatives of M. ovipneumoniae. Glucose-fermenting fried egg-like colonies identified as M. ovipneumoniae were obtained after a culture of tracheobronchial lavage from infected sheep. The genomes were sequenced, de novo assembled and comparatively evaluated. Important putative virulence factors were detected in all isolates: the analysis of the average nucleotide homology of all these genes with the M. ovipneumoniae ATCC 29419 revealed associations between clpB, lgt, tuf, and dnaJ genes and geographic location. In addition, nucleotide substitutions in a few positions of the Quinolone-Resistant Determinant Region of the gyrA gene, including the Ser83Ala, were detected. The phylogenomic analysis showed that the Brazilian isolates belonged to two different clades corresponding to geographic location, and the isolates from São Paulo showed high similarity, which differs from isolates from Rio de Janeiro. This first genomic analysis of the Brazilian M. ovipneumoniae genomes demonstrates strain segregation according to location and health status, reinforcing the importance of continuous surveillance and diagnostics of this bacteria causing sheep respiratory disease in the Brazilian flocks.

Life Table Study of Liriomyza trifolii and Its Contribution to Thermotolerance: Responding to Long-Term Selection Pressure for Abamectin Resistance.

Liriomyza trifolii is a significant invasive pest that targets horticultural and vegetable crops, causing large-scale outbreaks characterized by pronounced thermotolerance and insecticide resistance. This study examined the impact of long-term selection for abamectin resistance during the larval stage of L. trifolii on its population dynamics and thermal tolerance. We conducted a comprehensive comparison between the abamectin-resistant strain (AB-R) and the susceptible strain (S), including age-stage, two-sex life table analysis, thermal preference (Tpref), critical thermal maximum (CTmax), heat knockdown times (HKDTs), eclosion and survival rates, and LtHsp expression under heat stress. Our results showed that while selection for abamectin resistance was detrimental to survival and reproduction, it activated self-defense mechanisms and rapid adaptive adjustments and conferred modest thermal tolerance, which suggests a dual nature of insecticide effects. The AB-R strain exhibited significantly higher thermal preference and CTmax values, along with a longer HKDT and improved survival. Additionally, there was a significant upregulation of LtHsp expression in the AB-R strain compared to the S strain. These findings indicate that the evolution of thermal adaptation was accompanied by abamectin resistance development, emphasizing the necessity of considering temperature effects when applying chemical control. Our study provides valuable insights into how physiological acclimation may help mitigate the toxic effects of insecticides and illustrate how insects respond to multiple environmental pressures.

Comparison of germline and somatic structural variants in cancers reveal systematic differences in variant generating and selection processes.

Although several recent studies have characterized structural variants (SVs) in germline and cancer genomes, the features of SVs in these different contexts have not been directly compared. We examined similarities and differences between 2 million germline and 115 thousand tumor SVs from a cohort of 963 patients from The Cancer Genome Atlas (TCGA). We found significant differences in features related to their genomic sequences and localization that suggest differences between SV-generating processes and selective pressures. For example, we found that transposon-mediated processes shape germline much more than somatic SVs, while somatic SVs more frequently show features characteristic of chromoanagenesis. These differences were extensive enough to enable us to develop a classifier-"the great GaTSV"-that accurately distinguishes between germline and cancer SVs in tumor samples that lack a matched normal sample.