Biology subjects

Khan, I.

Publications and source records attributed to Khan, I..

At least 37 records · Page 2Linked to original sources

bioRxiv2024

Evolutionary history with chronic malnutrition enhances pathogen susceptibility at older ages

Juvenile malnutrition is a global public health concern that negatively impacts the development and maturation of the immune system, leading to increased susceptibility to infectious diseases. Such adverse effects on immunity might increase with ageing, worsening disease conditions later in life. Furthermore, malnutrition may persist across generations, imposing strong natural selection to survive the nutrient shortage. However, it is unclear how the evolutionary history of ancestral generations with chronic malnutrition could influence pathogen resistance and infection susceptibility, as well as their age-specific changes in extant generations. To address this, we used Drosophila melanogaster populations adapted against chronic juvenile malnutrition and exposed them to a bacterial pathogen, Providencia rettgeri, during their early and late adulthood. Surprisingly, we observed that in populations adapted to chronic malnutrition, young flies survived infection better by tolerating the infection, while control flies displayed higher infection susceptibility despite carrying a similar pathogen load. However, this pattern in post-infection survival is reversed with ageing. There was no change in pathogen resistance, but evolved flies succumbed more to infection than control flies regardless of the input infection doses. Our study thus revealed new evolutionary insights into the development of contrasting early vs late-life immune strategies and age-specific vulnerabilities to infection as a function of early-life malnutrition.

evolutionary biology↗

bioRxiv2024

Microbiota drives the sexually dimorphic infection outcomes in mealworm beetles

Sexually dimorphic responses to pathogenic infections in animals may stem from sex-specific differences in their life history and immune investment. Recent evidence highlights that such sex-specific variations in immune responses can also be critically regulated by microbiota. However, direct experiments to test how microbiota jointly impacts sex-specific immunity and vulnerability to pathogens are still limited. To this end, we used Tenebrio molitor beetles to first establish that sexes appear to differ in their microbiota composition and infection responses. Females were more vulnerable to bacterial infections and carried a higher bacterial load than males. When we depleted the microbiome, only females improved their post-infection survival, leading to a loss of sex-specific infection outcomes. Males, on the other hand, remained unaffected. Microbiota reconstitution (via feeding on faecal matter) of microbiota-depleted females increased their susceptibility to infection again, restoring the sexual dimorphism. We thus found a causal association between microbiome and infection responses. We also found reduced expression of an antimicrobial peptide tenecin 1 in females, which could be associated with their higher infection susceptibility, but such immune gene-vs-phenotypic associations were not consistent across microbiota manipulations. Immune strategies that are required to mediate the causal links between microbiome and infection response might thus vary with microbiota manipulations, warranting future investigations.

evolutionary biology↗

bioRxiv2024

Fig4 confers tolerance to rapamycin in a Ste20-dependent manner independent of the Vac14 scaffold

Summary StatementDisease-related Fig4 mutants displaying impaired association with the Fab1-Vac14-Fig4 complex confer tolerance to rapamycin in Saccharomyces cerevisiae independent of Vac14 in a Ste20-dependent manner. Fig4 can thus modulate homeostasis through association with pathways outside of the Fab1-Vac14-Fig4 complex in yeast. The lipid phosphatase Fig4 modulates the production and turnover of the signaling lipid PI3,5P2 through participation in a complex with its opposing kinase, Fab1, and the scaffold protein Vac14. Fig4 point mutations are associated with neurological diseases for which there are currently no specific therapies. Pathology involving Fig4 is generally attributed to disruption of the Fab1-Vac14-Fig4 complex. Through genetic manipulations in yeast we show that expression of Fig4 disease-related mutants confers tolerance to rapamycin, an inhibitor of the master growth activator TORC1. This phenotype is dominantly conferred at high temperatures by Fig4 mutants that bind poorly to Vac14 or by excess wild-type Fig4. Rapamycin tolerance does not require Fig4 catalytic activity or Vac14, suggesting that Fig4 mediates this altered stress response through context-inappropriate binding interactions with unknown proteins. The p21-activated kinase Ste20 is specifically required for this novel Vac14-independent Fig4 function. Our study shows that Fig4 can modulate homeostasis in Saccharomyces cerevisiae through interactions outside the Fab1-Vac14-Fig4 complex.

cell biology↗

bioRxiv2024

Genome assembly and annotation of the red flour beetle (Tribolium castaneum) from India

The largest insect order, Coleoptera, includes several economically important beetles that also serve as major model species for biological research. Perhaps foremost among these is the red flour beetle, a global pest of stored grains and flour whose genome was sequenced in 2008. However, the currently available reference genome (Tcas5.2) is incomplete, fragmented and contains many gaps, and the Y chromosome is not assembled. Here we present inTcas1, an updated genome assembly and annotation of T. castaneum collected from India, assembled using both short and long read sequencing, and annotated using two transcriptome datasets. We report that inTcas1 has fewer gaps, less fragmentation, and many new genes and new isoforms of previously annotated genes. This new resource provides a useful update, comparison, and reference for new beetle genome assemblies. The first Y chromosome assembly for this species also provides critical data to study the evolution of insect sex chromosomes and sex determination systems. SIGNIFICANCEWe present here an improved T. castaneum genome assembly (inTcas1) for beetles sampled from India, including the first Y chromosome of this important pest and laboratory model species. The new genome should facilitate more comprehensive analysis of Coleoptera genome and transcriptome datasets, especially beetle populations from Asia - the previously available genome, Tcas5.2, was assembled using the GA2 strain from USA. The updated genome should also facilitate analyses of genome evolution, including sex determination and sex chromosome dynamics; and the new gene annotations can expand the genetic toolkit for this beetle.

genomics↗

bioRxiv2024

PATHOGEN GROWTH AND VIRULENCE DYNAMICS DRIVE THE HOST EVOLUTION AGAINST COINFECTIONS

Coinfections, or the simultaneous infection of hosts by multiple pathogens, are widespread in nature with significant negative impacts on global health. Can hosts evolve against such coinfections as effectively as they would against individual pathogens? Also, what roles do individual pathogens play during such evolution? Here, we combined theoretical models and experiments with Tribolium castaneum populations evolving against two coinfecting bacterial pathogens, with contrasting growth and virulence dynamics, to reveal that fast-growing pathogens inflicting rapid mortality surges (i.e., fast-acting) restrict adaptive success against coinfections. While hosts rapidly evolved better survival against slow-growing bacteria causing long-lasting infections, evolution against coinfection was significantly delayed and resembled slow adaptation against fast-acting pathogens. Moreover, limited scopes of immunomodulation against fast-acting pathogens during coinfections can drive the observed adaptive patterns. Overall, we provide new insights into how adaptive dynamics and mechanistic bases against coinfections are critically regulated by individual pathogens growth and virulence dynamics.

evolutionary biology↗

bioRxiv2024

Characterization of the novel SmsHSP24.1 Promoter: Unveiling its abiotic stress-inducible expression in transgenic Eggplant (Solanum melongena L.)

Promoters play a pivotal role in regulating gene expression, orchestrating vital processes in plants, including their responses to various environmental stresses. In this study, we focus on the comprehensive characterization of the SmsHSP24.1 promoter, a novel cis-acting element, within the context of transgenic Eggplant (Solanum melongena L.). This detailed analysis shed light on the intricate mechanisms governing SmsHSP24.1 promoter-driven gene regulation, particularly in response to adverse environmental challenges such as heat, salt and drought stressors offering valuable insights into its role in plant stress adaptation. The advances in our understanding of promoter-driven gene regulation also contribute to the broader goal of enhancing crop resilience to abiotic stresses, positioning the SmsHSP24.1 promoter as a promising tool in agricultural biotechnology applications. HighlightsO_LIDemonstrated that the full-length 2.0 kb SmsHSP24.1 promoter significantly enhances gene expression under heat stress, with an observable decline in expression with promoter truncation. C_LIO_LIIdentified specific regulatory elements within the SmsHSP24.1 promoter that are decisive for inducible expression in response to abiotic stresses such as heat, salt, and drought. C_LIO_LIHighlighted the utility of the SmsHSP24.1 promoter in crop improvement programs, offering a tool for developing transgenic plant tolerance to combined stresses. C_LI

plant biology↗

bioRxiv2023

Model-based inference of a plant-specific dual role for HOPS in regulating guard cell vacuole fusion

Stomata are the pores on a leaf surface that regulate gas exchange. Each stoma consists of two guard cells whose movements regulate pore opening and thereby control CO2 fixation and water loss. Guard cell movements depend in part on the remodeling of vacuoles, which have been observed to change from a highly fragmented state to a fused morphology during stomata opening. This change in morphology requires a membrane fusion mechanism that responds rapidly to environmental signals, allowing plants to respond to diurnal and stress cues. With guard cell vacuoles being both large and responsive to external signals, stomata represent a unique system in which to delineate mechanisms of membrane fusion. Fusion of vacuole membranes is a highly conserved process in eukaryotes, with key roles played by two multi-subunit complexes: HOPS (homotypic fusion and vacuolar protein sorting) and SNARE (soluble NSF attachment protein receptor). HOPS is a vacuole tethering factor that is thought to chaperone SNAREs from apposing vacuole membranes into a fusion-competent complex capable of rearranging membranes. To resolve a counter-intuitive observation regarding the role of HOPS in regulating plant vacuole morphology, we derived a quantitative model of vacuole fusion dynamics and used it to generate testable predictions about HOPS-SNARE interactions. We derived our model by applying simulation-based inference to integrate prior knowledge about molecular interactions with limited, qualitative observations of emergent vacuole phenotypes. By constraining the model parameters to yield the emergent outcomes observed for stoma opening - as induced by two distinct chemical treatments - we predicted a dual role for HOPS and identified a stalled form of the SNARE complex that differs from phenomena reported in yeast. We predict that HOPS has contradictory actions at different points in the fusion signaling pathway, promoting the formation of SNARE complexes, but limiting their activity. Author summaryPlants "breathe" through pores in their leaves where each pore is formed by two specialized cells called guard cells. To open these pores, guard cells change in volume. This volume change is controlled by water-filled organelles called vacuoles that morph from multiple small entities to a few large ones capable of taking up more water to reshape the cell. Specialized proteins in vacuole membranes make this change happen by pulling vacuoles together until they fuse. Some of these proteins reside in membranes, but others must be drawn to the membrane from the cells cytoplasm. Specific lipid molecules in the membrane play an important role in recruiting those proteins to the vacuole membrane. We previously made an unexpected finding that removing this lipid induces plant vacuole fusion. To make sense of this observation, we used a mathematical model to piece together our knowledge of the proteins involved in this process and what we know about the chemical treatments that cause vacuoles to morph. Using computer simulations, we uncovered new rules about how molecules interact in membranes to accomplish the task of vacuole fusion in plants. We think the rules uncovered through mathematical modeling allow plants to respond quickly to environmental cues.

systems biology↗

bioRxiv2023

Efficient Sequence Embedding For SARS-CoV-2 Variants Classification

Kernel-based methods, such as Support Vector Machines (SVM), have demonstrated their utility in various machine learning (ML) tasks, including sequence classification. However, these methods face two primary challenges:(i) the computational complexity associated with kernel computation, which involves an exponential time requirement for dot product calculation, and (ii) the scalability issue of storing the large n x n matrix in memory when the number of data points(n) becomes too large. Although approximate methods can address the computational complexity problem, scalability remains a concern for conventional kernel methods. This paper presents a novel and efficient embedding method that overcomes both the computational and scalability challenges inherent in kernel methods. To address the computational challenge, our approach involves extracting the k-mers/nGrams (consecutive character substrings) from a given biological sequence, computing a sketch of the sequence, and performing dot product calculations using the sketch. By avoiding the need to compute the entire spectrum (frequency count) and operating with low-dimensional vectors (sketches) for sequences instead of the memory-intensive n x n matrix or full-length spectrum, our method can be readily scaled to handle a large number of sequences, effectively resolving the scalability problem. Furthermore, conventional kernel methods often rely on limited algorithms (e.g., kernel SVM) for underlying ML tasks. In contrast, our proposed fast and alignment-free spectrum method can serve as input for various distance-based (e.g., k-nearest neighbors) and non-distance-based (e.g., decision tree) ML methods used in classification and clustering tasks. We achieve superior prediction for coronavirus spike/Peplomer using our method on real biological sequences excluding full genomes. Moreover, our proposed method outperforms several state-of-the-art embedding and kernel methods in terms of both predictive performance and computational runtime.

bioinformatics↗

bioRxiv2023

Dissociable encoding of motivated behavior by parallel thalamo-striatal projections

The successful pursuit of goals requires the coordinated execution and termination of actions that lead to positive outcomes. This process is thought to rely on motivational states that are guided by internal drivers, such as hunger or fear. However, the mechanisms by which the brain tracks motivational states to shape instrumental actions are not fully understood. The paraventricular nucleus of the thalamus (PVT) is a midline thalamic nucleus that shapes motivated behaviors via its projections to the nucleus accumbens (NAc)1-8 and monitors internal state via interoceptive inputs from the hypothalamus and brainstem3,9-14. Recent studies indicate that the PVT can be subdivided into two major neuronal subpopulations, namely PVTD2(+) and PVTD2(-), which differ in genetic identity, functionality, and anatomical connectivity to other brain regions, including the NAc4,15,16. In this study, we used fiber photometry to investigate the in vivo dynamics of these two distinct PVT neuronal types in mice performing a reward foraging-like behavioral task. We discovered that PVTD2(+) and PVTD2(-) neurons encode the execution and termination of goal-oriented actions, respectively. Furthermore, activity in the PVTD2(+) neuronal population mirrored motivation parameters such as vigor and satiety. Similarly, PVTD2(-) neurons, also mirrored some of these parameters but to a much lesser extent. Importantly, these features were largely preserved when activity in PVT projections to the NAc was selectively assessed. Collectively, our results highlight the existence of two parallel thalamo-striatal projections that participate in the dynamic regulation of goal pursuits and provide insight into the mechanisms by which the brain tracks motivational states to shape instrumental actions.

animal behavior and cognition↗

bioRxiv2023

The immune regulation and epidemiological consequences of immune priming in Drosophila

Invertebrates lack the immune machinery underlying vertebrate-like acquired immunity. However, in many insects past infection by the same pathogen can prime the immune response, resulting in improved survival upon reinfection. Here, we investigated the generality, specificity and mechanistic basis of innate immune priming in the fruit fly Drosophila melanogaster when infected with the gram-negative bacterial pathogen Providencia rettgeri. We find that priming in response to P. rettgeri infection is a long-lasting and pathogen-specific response. We further explore the epidemiological consequences of immune priming and find it has the potential to curtail pathogen transmission by reducing pathogen shedding and spread. The enhanced survival of individuals previously exposed to a non-lethal bacterial inoculum coincided with a transient decrease in bacterial loads, and we provide strong evidence that the effect of priming requires the IMD-responsive antimicrobial-peptide Diptericin-B in the fat body. Further, we show that while Diptericin B is the main effector of bacterial clearance, it is not sufficient for immune priming, which requires regulation of IMD by peptidoglycan recognition proteins. This work underscores the plasticity and complexity of invertebrate responses to infection, providing novel experimental evidence for the effects of innate immune priming on population-level epidemiological outcomes.

immunology↗

bioRxiv2022

Wound healing and anti-inflammatory potential of Ajuga bracteosa-conjugated silver nanoparticles in Balb/c mice

BackgroundWound therapy is complicated, uncomfortable for the patient, and costly for the health-care system. Silver nanoparticles (AgNP) have antibacterial characteristics that can prevent bacterial infection in wounds and speed up wound healing ObjectiveThe aim of current research was to investigate the wound healing and anti-inflammatory potential of biogenic synthesized silver nanoparticles (ABAgNP) using Ajuga bracteosa (ABaqu) in Swiss albino mice. MethodsIn vivo wound healing and anti-inflammatory activities were carried out using Bala/c mice. For in vivo screening of 200 mg/kg and 400 mg/kg of both ABAgNPs and ABaqu were used. Liver and kidney functional markers, hematology, and histopathological studies were carried out after 14 days of administration. ResultsThe obtained biogenic nanoparticles were characterized, dermal toxicity, wound excision repairing, and formalin-induced paw edema assays were performed in Swiss albino mice. Dermal toxicity showed that tested concentrations of ABaqu and ABAgNPs were safe. No adverse effects, changes, and alteration in the skin of treatment groups as well as the control vehicle group (petroleum jelly) were recorded. Results revealed that the enhanced wound contraction was observed in ABaqu, ABAgNP, and the Nitrofuranose treated groups from 7th to 11thdays. The anti-inflammatory activity in formalin-induced paw edema model illustrated the potential use of silver nanoparticles ABAgNPs and ABaqu as a reducing or inflammation inhibiting agents due to the release of acute inflammatory mediators. ConclusionTherefore, it was concluded that both silver nanoparticles (ABAgNP) and Ajuga bracteosa (ABaqu) extracts could be used as a wound healing and anti-inflammatory agents.

zoology↗

bioRxiv2022

Albumin as a probe for clathrin-independent endocytosis and transcytosis into experimental brain metastases of breast cancer.

Advances in drug treatments for brain metastases of breast cancer have improved progression free survival but new, more efficacious strategies are needed. Most chemotherapeutic drugs infiltrate brain metastases by moving between brain capillary endothelial cells, paracellular distribution, resulting in heterogeneous distribution, lower than that to systemic metastases. Herein, we tested three well-known transcytotic pathways through brain capillary endothelial cells as potential avenues for drug access: Transferrin receptor (TfR) peptide, Low density lipoprotein receptor 1 (LRP1) peptide, Albumin. Each was far-red labeled, injected into two hematogenous models of brain metastases, circulated for two different times, and their uptake quantified in metastases and uninvolved (nonmetastatic) brain. Surprisingly, all three pathways demonstrated distinct distribution patterns in vivo. Two were suboptimal: TfR distributed to uninvolved brain but poorly in metastases, while LRP1 was poorly distributed. Albumin distributed to virtually all metastases in both model systems, significantly greater than in uninvolved brain (P <0.0001). Further experiments revealed that albumin entered both macrometastases and micrometastases, the targets of treatment and prevention translational strategies. Albumin uptake into brain metastases was not correlated with the uptake of a paracellular probe (biocytin). We identified a novel mechanism of albumin endocytosis through the endothelia of brain metastases consistent with clathrin-independent endocytosis (CIE), involving the neonatal Fc receptor (FcRn), galectin-3 (Gal-3) and glycosphingolipids. Components of the CIE process were found on metastatic endothelial cells in human craniotomies. The data suggest a reconsideration of albumin as a translational mechanism for improved drug delivery to brain metastases and possibly other CNS cancers. Statement of SignificanceDrug therapy for brain metastasis needs improvements. We surveyed transcytotic pathways as potential delivery systems in brain-tropic models and found that albumin has optimal properties. Albumin used a novel mechanism for endocytosis.

cancer biology↗

bioRxiv2022

Disruption of flour beetle microbiota limits experimentally evolved immune priming response, but not pathogen resistance

Host-associated microbiota play a fundamental role in the training and induction of different forms of immunity, including inducible as well as constitutive components. However, direct experiments analysing the relative importance of microbiota during evolution of different immune functions are missing. We addressed this gap by using experimentally evolved lines of Tribolium castaneum that either produced inducible immune memory-like responses (immune priming) or constitutively expressed basal resistance (without priming), as mutually exclusive strategies against Bacillus thuringiensis infection. We disrupted the microbial communities in these evolved lines and estimated the impact on the beetles ability to mount a priming response vs basal resistance. Populations that had evolved immune priming lost the ability to mount a priming response upon microbiota disruption. Microbiota manipulation also caused a drastic reduction in their reproductive output and post-infection longevity. In contrast, in pathogen-resistant beetles, microbiota manipulation did not affect post-infection survival or reproduction. The divergent evolution of immune responses across beetle lineages was thus associated with divergent reliance on the microbiome. Whether the latter is a direct outcome of differential pathogen exposure during selection or reflects evolved immune functions remains unclear. We hope that our results will motivate further experiments to understand the mechanistic basis of these complex evolutionary associations between microbiota, host immune strategies, and fitness outcomes.

evolutionary biology↗

bioRxiv2022

Ageing leads to nonspecific antimicrobial peptide responses in Drosophila melanogaster

Evolutionary theory predicts a late-life decline in the force of natural selection, possibly leading to late-life deregulations of the immune system. A potential outcome of such immune-deregulation is the inability to produce specific immunity against target pathogens. We tested this possibility by infecting multiple Drosophila melanogaster lines (with bacterial pathogens) across age-groups, where either individual or different combinations of Imd- and Toll-inducible antimicrobial peptides (AMPs) were deleted using CRISPR gene editing. We show a high degree of non-redundancy and pathogen-specificity of AMPs in young flies: in some cases, even a single AMP could confer complete resistance. In contrast, ageing led to a complete loss of such specificity, warranting the action of multiple AMPs across Imd- and Toll-pathways during infections. Moreover, use of diverse AMPs either had no survival benefits, or even accompanied survival costs post-infection. These features were also sexually dimorphic: females expressed a larger repertoire of AMPs than males, but extracted equivalent survival benefits. Finally, age-specific expansion of the AMP-pool was associated with downregulation of negative-regulators of the Imd-pathway and a potential damage to renal function, as features of poorly-regulated immunity, Overall, we could establish ageing as an important driver of nonspecific AMP responses, across sexes and bacterial infections.

immunology↗

bioRxiv2022

Interaction of Fungal lipase with potential phytotherapeutics

Interaction of thymol, carvacrol and linalool with fungal lipase and Human Serum Albumin (HSA) have been investigated employing UV-Vis, Fluorescence and Circular dichroism spectroscopy along with docking studies. Thymol, carvacrol and linalool displayed approximately 50% inhibition at 1.5 mmol/litre concentrations using para-nitrophenyl palmitate. UV-Vis spectroscopy give evidence of the formation of lipase-linalool, lipasecarvacrol and lipase-thymol complex at the ground state. Three molecules also showed complex formation with HSA at the ground state. Fluorescence spectroscopy shows strong binding of lipase to thymol (Ka of 2.6 x 109 M-1) as compared to carvacrol (4.66 x 107 M-1) and linalool (5.3 x 103 M-1). Number of binding sites showing stoichiometry of association process on lipase is found to be 2.52 (thymol) compared to 2.04 (carvacrol) and 1.12 (linalool). Secondary structure analysis by CD spectra results, following 24 hours incubation at 25{degrees}C, with thymol, carvacrol and linalool revealed decrease in negative ellipticity for lipase indicating loss in helical structure as compared with the native protein. The lowering in negative ellipticity was in the order of thymol > carvacrol > linalool. Results of Fluorescence and CD spectroscopy taken together suggests that thymol and carvacrol are profound disrupter of lipase structure. Fluorescence spectra following binding of all three molecules with HSA caused blue shift which suggests the compaction of the HSA structure. Association constant of thymol and HSA is 9.6 x 108 M-1 which along with n value of 2.41 suggests strong association and stable complex formation, association constant for carvacrol and linalool was in range of 107 and 103 respectively. Docking results give further insight into strong binding of thymol, carvacrol and linalool with lipase having free energy of binding as -7.1 kcal/mol, -5.0 kcal/mol and -5.2 kcal/mol respectively. To conclude, fungal lipases can be attractive target for controlling their growth and pathogenicity. Employing UV-Vis, Fluorescence and Circular dichroism spectroscopy we have shown that thymol, carvacrol and linalool strongly bind and disrupt structure of fungal lipase, these three phytochemicals also bind well with HSA. Best anti-lipase molecules based on disruption of lipase structure and HSA structure conservation is thymol.

biophysics↗

bioRxiv2021

ASSOCIATION STUDY OF SIX CANDIDATE GENES WITH MAJOR DEPRESSIVE DISORDER IN THE NORTH-WESTERN POPULATION OF PAKISTAN

People around the world are currently affected by Major Depressive Disorder (MDD). Despite its many aspects, symptoms, manifestations and impacts, efforts have been made to identify the root causes of the disorder. In particular, genetic studies have concentrated on identifying candidate genes for MDD and exploring associations between these genes and some specific group of individuals. The aim of this research was to find out the association between single nucleotide polymorphisms in 6 candidate genes linked to the neurobiology of major depressive disorder in the North-Western population of Pakistan. We performed a case-control analysis, with 400 MDD and 232 controls. A trained psychiatrist or clinical psychologists evaluated the patients. Six polymorphisms were genotyped and tested for allele and genotype association with MDD. There were no statistical variations between MDD patients and healthy controls for genotypic and allelic distribution of all the polymorphisms observed. Thus, our analysis does not support the major role of these polymorphisms in contributing to MDD susceptibility, although it does not preclude minor impact. The statistically significant correlation between six polymorphisms and major depressive disorder in the studied population was not observed. There are inconsistencies in investigations around the world. Future research, including GWAS and association analysis on larger scale should be addressed for further validation and replication of the present findings.

genetics↗

bioRxiv2020

Sexual conflict drives micro- and macroevolution of sexual dimorphism in immunity

BackgroundSexual selection can have major effects on mating rates and sex-specific costs of mating and may thereby influence sex-differences in immunity as well as associated host-pathogen dynamics. Yet, experimental evidence linking the mating system to evolved sexual dimorphism in immunity are scarce and the direct effects of mating rate on immunity are not well established. Here, we use transcriptomic analyses, experimental evolution and phylogenetic comparative methods to study the association between the mating system and sexual dimorphism in immunity in seed beetles, where mating causes internal injuries in females. ResultsWe demonstrate that female phenoloxidase (PO) activity, involved in wound healing and defence against parasitic infections, is elevated relative to males. This difference is accompanied by concomitant sex-differences in the expression of genes in the pro-phenoloxidase activating cascade. We document substantial phenotypic plasticity in female PO activity in response to mating and show that experimental evolution under enforced monogamy (resulting in low remating rates and sexual conflict relative to natural polygamy) rapidly decreases female (but not male) PO activity. Moreover, monogamous females have evolved increased tolerance to bacterial infection unrelated to mating, implying that female responses to costly mating may trade off with other aspects of immune defence, an hypothesis which broadly accords with the documented sex differences in gene expression. Finally, female (but not male) PO activity shows correlated evolution with the perceived harmfulness of male genitalia across 12 species of seed beetles, suggesting that sexual conflict has a significant influence on sexual dimorphisms in immunity in this group of insects. ConclusionsOur study provides insights into the links between sexual conflict and sexual dimorphism in immunity at the molecular and phenotypic level and suggests that selection pressures moulded by mating interactions can lead to a sex-specific mosaic of immune responses with important implications for host-pathogen dynamics in sexually reproducing organisms.

evolutionary biology↗

bioRxiv2020

Bio-Orthogonal Chemistry Enables Solid Phase Synthesis of Long RNA Oligonucleotides

Solid phase synthesis of RNA oligonucleotides which are over 100-nt in length remains to be challenging due to the complexity of purification of the target strands from the failure sequences. This work describes a non-chromatographic strategy that will enable routine solid phase synthesis of long RNA strands. The optimized five-step process is based on bio-orthogonal inverse electron demand Diels-Alder chemistry between trans-cyclooctene (TCO) and tetrazine (Tz) and entails solid phase synthesis of RNA on a photo-labile support. The target oligonucleotide strands are selectively tagged with Tz. After photocleavage from the solid support, the target oligonucleotide strands can be captured and purified from the failure sequences using immobilized TCO. The approach was optimized using a model 20-mer DNA strand and was successfully applied towards synthesis of 76-nt long tRNA and 101-nt long sgRNA. Purity of the isolated oligonucleotides was evaluated using gel electrophoresis and mass spectrometry, while functional fidelity of the sgRNA was confirmed using CRISPR-Cas9 experiments and flow cytometry.

biochemistry↗