Biology subjects

Adhikari, P.

Publications and source records attributed to Adhikari, P..

13 recordsLinked to original sources

bioRxiv2026

Scalable longitudinal imaging and transcriptomics of cells in dynamic enclosures

Dynamic transitions between cell states underlie both normal physiology and disease. However, most single-cell technologies capture only static snapshots. To address this gap, we developed a platform that integrates light-guided hydrogel polymerization with computer vision to generate on-demand compartments around live cells, enabling longitudinal imaging of cellular behavior paired with whole-transcriptome profiling of the same cells at scale. These data link dynamic phenotypes with molecular programs, enabling deeper characterization of cellular states. This approach revealed an adaptive, drug-resistant state in lung cancer cells characterized by potassium channel upregulation and p53-dependent quiescence. In models of adipogenesis and microglial phagocytosis, joint analysis of imaging and transcriptomic data identified key drivers of cellular function that were missed by transcriptomic clustering alone. These results establish the value of paired functional and transcriptomic analysis to resolve molecular drivers of complex cellular behaviors.

systems biology↗

bioRxiv2025

The gut microbiome in early age-related macular degeneration

The gut microbiome is implicated in the development of advanced age-related macular degeneration (AMD) but no study has investigated microbial composition in early AMD nor controlled for important microbiome modulators such as diet and light. This is crucial as diet can change the microbiome rapidly as well as affects disease progression. In addition, the light signalling photoreceptors are dysfunctional in AMD. Here we determined the gut microbiota by conducting 16S DNA metagenomic sequencing of 40 faecal samples from 20 participants with and without early AMD. We normalised both groups to the same diet over 5 days and determined gut microbial composition before and after the diet. To control for light, we assessed habitual light exposure with actigraphy and the post-illumination pupil light response (PIPR) quantified photoreceptor signalling. Clostridium termitidis, Bacteroides gallinarum, and Bacteroides finegoldii were significantly abundant in early AMD compared to controls at both time points. Interestingly, pro-inflammatory species such as Sutterella were only significantly abundant in AMD before the diet. After the diet, the gut microbiome shifted to a significantly greater abundance of commensal bacteria in AMD. Controls and AMD patients had a similar ambient light exposure, however the PIPR was significantly reduced in AMD suggesting impaired light signalling. We are the first to show a distinct gut microbiome in early AMD and infer that dietary changes may positively affect the gut microbiome at early stage of the disease.

neuroscience↗

bioRxiv2024

Bond strength between receptor binding domain of spike protein and human angiotensin converting enzyme-2 using machine learning.

The spike protein (S-protein) of SARS-CoV-2 plays an important role in binding, fusion, and host entry. In this study, we have predicted interatomic bond strength between receptor binding domain (RBD) and angiotensin converting enzyme-2 (ACE2) using machine learning (ML), that matches with expensive ab initio calculation result. We collected bond order result from ab initio calculations. We selected a total of 18 variables such as bond type, bond length, elements and their coordinates, and others, to train ML models. We then trained five well-known regression models, namely, Decision Tree regression, KNN Regression, XGBoost, Lasso Regression, and Ridge Regression. We tested these models on two different datasets, namely, Wild type (WT) and Omicron variant (OV). In the first setting, we used 90% of each dataset for training and 10% for testing to predict the bond order. XGBoost model outperformed all the other models in the prediction of the WT dataset. It achieved an R2 Score of 0.997. XGBoost also outperformed all the other models with an R2 score of 0.9998 in the prediction of the OV dataset. In the second setting, we trained all the models on the WT (or OV) dataset and predicted the bond order on the OV (or WT) dataset. Interestingly, Decision Tree outperformed all the other models in both cases. It achieved an R2 score of 0.997.

biophysics↗

bioRxiv2024

Intercontinental dissemination and diversification of Xanthomonas perforans in tomato production

Emerging and re-emerging plant diseases continue to present multifarious threats to global food security. Considerable recent efforts are therefore being channeled towards understanding the nature of pathogen emergence, their spread and evolution. Xanthomonas euvesicatoria pv. perforans (Xep), one of the causal agents of bacterial spot of tomato, rapidly emerged and displaced other bacterial spot xanthomonads in tomato production regions around the world. In less than three decades, it has become a dominant xanthomonad pathogen in tomato production systems across the world and presents a model for understanding diversification of recently emerged bacterial plant pathogens. Although Xep has been continuously monitored in Florida since its discovery, the global population structure and evolution at the genome-scale is yet to be fully explored. The objectives of this work were to determine genetic diversity globally to ascertain if different tomato production regions contain genetically distinct Xep populations, to examine genetic relatedness of strains collected in tomato seed production areas in East Asia and other production regions, and to evaluate variation in type III effectors, which are critical pathogenicity and virulence factors, in relationship to population structure. We used genome data from 270 strains from 13 countries for phylogenetic analysis and characterization of Xop effector gene diversity among strains. Our results showed notable genetic diversity in the pathogen. We found genetically similar strains in distant tomato production regions, including seed production regions, and diversification over the past 100 years, which is consistent with intercontinental dissemination of the pathogen in hybrid tomato production chains. Evolution of the Xep pangenome, including the acquisition and loss of type III secreted effectors, is apparent within and among phylogenetic lineages. The apparent long-distance movement of the pathogen, together with variants that may not yet be widely distributed, poses risks of emergence of new variants in tomato production.

microbiology↗

bioRxiv2022

Impact of BA.1, BA.2, and BA.4/BA.5 Omicron Mutations on Therapeutic Monoclonal Antibodies

The emergence of Omicron SARS-CoV-2 subvariants (BA.1, BA.2, BA.4, and BA.5) with an unprecedented number of mutations in their receptor-binding domain (RBD) of the spike-protein has fueled a new surge of COVID-19 infections, posing a major challenge to the efficacy of existing vaccines and monoclonal antibody (mAb) therapeutics. Here, a thorough and systematic molecular dynamics (MD) simulation study is conducted to investigate how the RBD mutations on these subvariants affect the interactions with broad mAbs including AstraZeneca (COV2-2196 and COV2-2130), Brii Biosciences (BRII-196), Celltrion (CT-P59), Eli Lilly (LY-CoV555 and LY-CoV016), Regeneron (REGN10933 and REGN10987), Vir Biotechnology (S309), and S2X259. Our results show a complete loss of binding for COV2-2196, BRII-196, CT-P59, and LY-CoV555 with all Omicron RBDs. REGN10987 also loses its binding against BA.1 but partially retains against BA.2 and BA.4/5. The reduction in binding is either significant for LY-CoV016 and REGN10933 or moderate for COV2-2130. S309 and S2X259 retain their binding strength against BA.1 but decrease against others. We introduce a mutational escape map for each mAb to identify the key RBD sites and critical mutation. Overall, our findings suggest that majority of therapeutic mAbs have diminished or lost their activity against Omicron subvariants, indicating the urgent need for a new therapeutic mAb, modifying current ones with a better mAb design, or seeking an alternative approach.

biophysics↗

bioRxiv2022

Effect of Delta and Omicron mutations on the RBD-SD1 do-main of the Spike protein in SARS-CoV-2 and the Omicron mutations on RBD-ACE2 interface complex

The receptor-binding domain (RBD) is the essential part in the Spike-protein (S-protein) of SARS-CoV-2 virus that directly binds to the human ACE2 receptor, making it a key target for many vaccines and therapies. Therefore, any mutations at this domain could affect the efficacy of these treatments as well as the viral-cell entry mechanism. We introduce ab initio DFT-based computational study that mainly focuses on two parts: (1) Mutations effects of both Delta and Omicron variants in the RBD-SD1 domain. (2) Impact of Omicron RBD mutations on the structure and properties of the RBD-ACE2 interface system. The in-depth analysis is based on the novel concept of amino acid-amino acid bond pair units (AABPU) that reveal the differences between the Delta and/or Omicron mutations and its corresponding wild-type strain in terms of the role played by non-local amino acid interactions, their 3D shapes and sizes, as well as contribution to hydrogen bonding and partial charge distributions. Our results also show that the interaction of Omicron RBD with ACE2 significantly increased its bonding between amino acids at the interface providing information on the implications of penetration of S-protein into ACE2, and thus offering a possible explanation for its high infectivity. Our findings enable us to present in more conspicuous atomic level detail the effect of specific mutations that may help in predicting and/or mitigating the next variant of concern.

biochemistry↗

bioRxiv2022

Atomic-scale Quantum Chemical Calculation of Omicron Mutations Near Cleavage Sites of the Spike Protein

The attachment of the Spike-protein in SARS-CoV-2 to host cells and the initiation of viral invasion are two critical processes in the viral infection and transmission processes in which the presence of unique furin (S1/S2) and TMPRSS2 (S2) cleavage sites play a pivotal role. In this study, we provide detailed analysis of the impact of the BA.1 Omicron variant mutations, vicinal to these two cleavage sites using a novel computational method based on Amino acid - amino acid bond pair unit (AABPU), a specific protein structural unit in 3D as a proxy for quantifying the atomic interaction. We have identified several key features related to the electronic structure as well as bonding of the Omicron mutations near the cleavage sites that significantly increase the size of the relevant AABPUs and the fraction of the positive partial charge. These results of the ultra-large-scale quantum calculations enable us to conjecture on the biological role of Omicron mutations and their specific effects on cleavage sites, as well as identify the principles that can be of some value in analyzing other new variants or subvariants.

biophysics↗

bioRxiv2022

Binding Interactions between RBD of Spike-Protein and Human ACE2 in Omicron variant

Emergence of new SARS-CoV-2 Omicron VOC (OV) has exacerbated the COVID-19 pandemic due to a large number of mutations in the spike-protein, particularly in the receptor-binding domain (RBD), resulting in highly contagious and/or vaccine-resistant strain. Herein, we present a systematic analysis based on detailed molecular dynamics (MD) simulations in order to understand how the OV RBD mutations affect the ACE2 binding. We show that the OV RBD binds to ACE2 more efficiently and tightly due predominantly to strong electrostatic interactions, thereby promoting increased infectivity and transmissibility compared to other strains. Some of OV RBD mutations are predicted to affect the antibody neutralization either through their role in the S-protein conformational changes, such as S371L, S373P, and S375F, or through changing its surface charge distribution, such as G339D, N440K, T478K, and E484A. Other mutations, such as K417N, G446S, and Y505H, decrease the ACE2 binding, whereas S447N, Q493R, G496S, Q498R, and N501Y tend to increase it. TOC GRAPHICS O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/480009v1_ufig1.gif" ALT="Figure 1"> View larger version (102K): org.highwire.dtl.DTLVardef@88f654org.highwire.dtl.DTLVardef@1e42d14org.highwire.dtl.DTLVardef@14b7d04org.highwire.dtl.DTLVardef@fca7d0_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2022

Mutations of Omicron variant at the interface of the receptor domain motif and human angiotensin-converting enzyme-2

The most recent Omicron variant of SARS-CoV-2 has caused global concern and anxiety. The only thing certain about this strain, with large number of mutations in the spike protein, is that it spreads quickly, seems to evade immune defense and mitigates the benefits of existing vaccines. Based on the ultra-large-scale ab initio computational modeling of the receptor binding motif (RBM) and human angiotensin-converting enzyme-2 (ACE2) interface we provide the details of the effect of Omicron mutations at the fundamental atomic scale level. In-depth analysis anchored in the novel concept of amino acid-amino acid bond pair units (AABPU), indicates that mutations in the Omicron variant are connected with (i) significant changes in the shape and structure of AABPU components, together with (ii) significant increase in the positive partial charge which facilitates the interaction with ACE2. The calculated bond order, based on AABPU, reveals that the Omicron mutations increase the binding strength of RBM to ACE2. Our findings correlate with and are instrumental to explain the current observations and can contribute to the prediction of next potential new variant of concern.

biophysics↗

bioRxiv2021

Delta variant with P681R critical mutation revealed by ultra-large atomic-scale ab initio simulation: Implications for the fundamentals of biomolecular interactions

SARS-CoV-2 Delta variant is emerging as a globally dominant strain. Its rapid spread and high infection rate are attributed to a mutation in the spike protein of SARS-CoV-2 allowing the virus to invade human cells much faster and with increased efficiency. Particularly, an especially dangerous mutation P681R close to the furin cleavage site has been identified as responsible for increasing the infection rate. Together with the earlier reported mutation D614G in the same domain, it offers an excellent instance to investigate the nature of mutations and how they affect the interatomic interactions in the spike protein. Here, using ultra large-scale ab initio computational modeling, we study the P681R and D614G mutations in the SD2-FP domain including the effect of double mutation and compare the results with the wild type. We have recently developed a method of calculating the amino acid-amino acid bond pairs (AABP) to quantitatively characterize the details of the interatomic interactions, enabling us to explain the nature of mutation at the atomic resolution. Our most significant find is that the mutations reduce the AABP value, implying a reduced bonding cohesion between interacting residues and increasing the flexibility of these amino acids to cause the damage. The possibility of using this unique mutation quantifiers in a machine learning protocol could lead to the prediction of emerging mutations.

biochemistry↗

bioRxiv2021

Balancing growth amidst salinity stress-lifestyle perspectives from the extremophyte model Schrenkiella parvula

Schrenkiella parvula, a leading extremophyte model in Brassicaceae, can grow and complete its life cycle under multiple environmental stresses, including high salinity. While foundational genomic resources have been created for S. parvula, a comprehensive physiological or structural characterization of its salt stress responses is absent. We aimed to identify the influential traits that lead to stress-resilient growth of this species. We examined salt-induced changes in the physiology and anatomy of S. parvula throughout its lifecycle across multiple tissues. We found that S. parvula maintains or even exhibits enhanced growth during various developmental stages at salt stress levels known to inhibit growth in Arabidopsis and most crops. The resilient growth of S. parvula was associated with key traits that synergistically allow continued primary root growth, expansion of xylem vessels across the root-shoot continuum, and a high capacity to maintain tissue water levels by developing larger and thicker leaves while facilitating continued photosynthesis during salt stress. These traits at the vegetative phase were followed by a successful transition to the reproductive phase via early flowering, development of larger siliques, and production of viable seeds during salt stress. Additionally, the success of self-fertilization during early flowering stages was dependent on salt-induced filament elongation in flowers that aborted in the absence of salt. Our results suggest that the maintenance of leaf water status and enhancement of selfing in early flowers to ensure reproductive success, are among the most influential traits that contribute to the extremophyte lifestyle of S. parvula in its natural habitat. One sentence summarySchrenkiella parvula salt-resilient growth is facilitated by uncompromised primary root growth, expansion of xylem vessels, maintenance of leaf water status and photosynthesis, and early flowering.

plant biology↗

bioRxiv2020

Genetic variation associated with PPO-inhibiting herbicide tolerance in sorghum

Herbicide application is crucial for weed management in most crop production systems, but for sorghum herbicide options are limited. Sorghum is sensitive to residual protoporphyrinogen oxidase (PPO)- inhibiting herbicides, such as fomesafen, and a long re-entry period is required before sorghum can be planted after its application. Improving sorghum for tolerance to such residual herbicides would allow for increased sorghum production and the expansion of herbicide options for growers. To investigate the underlying mechanism of tolerance to residual fomesafen, a genome-wide association mapping study was conducted using the sorghum biomass panel (SBP) and field-collected data, and a greenhouse assay was developed to confirm the field phenotypes. A total of 26 significant SNPs (FDR<0.05), spanning a 215.3 kb region, were detected on chromosome 3. The ten most significant SNPs included two in genic regions (Sobic.003G136800, and Sobic.003G136900) and eight SNPs in the intergenic region encompassing the genes Sobic.003G136700, Sobic.003G136800, Sobic.003G137000, Sobic.003G136900, and Sobic.003G137100. The gene Sobic.003G137100 (PPXI), which encodes the PPO1 enzyme, one of the targets of PPO-inhibiting herbicides, was located 12kb downstream of the significant SNP S03_13152838. We found that PPXI is highly conserved in sorghum and expression does not significantly differ between tolerant and sensitive sorghum lines. Our results suggest that PPXI most likely does not underlie the observed herbicide tolerance. Instead, the mechanism underlying herbicide tolerance in the SBP is likely metabolism-based resistance, possibly regulated by the action of multiple genes. Further research is necessary to confirm candidate genes and their functions.

plant biology↗

bioRxiv2017

Mef2 induction of the immediate early gene Hr38/Nr4a is terminated by Sirt1 to promote ethanol tolerance

Drug naive animals given a single dose of ethanol show changed responses to subsequent doses, including the development of ethanol tolerance and ethanol preference. These simple forms of behavioral plasticity are due in part to changes in gene expression and neuronal properties. Surprisingly little is known about how ethanol initiates changes in gene expression or what the changes do. Here we demonstrate a role in ethanol plasticity for Hr38, the sole Drosophila homolog of the mammalian Nr4a1/2/3 class of immediate early response transcription factors. Acute ethanol exposure induces transient expression of Hr38 and other immediate early neuronal activity genes. Ethanol activates the Mef2 transcriptional activator to induce Hr38, and the Sirt1 histone/protein deacetylase terminates Hr38 induction. Loss of Hr38 decreases ethanol tolerance and causes precocious but short-lasting ethanol preference. Similarly, reduced Mef2 activity in all neurons or specifically in the mushroom body /{beta} neurons decreases ethanol tolerance; Sirt1 promotes ethanol tolerance in these same neurons. Genetically decreasing Hr38 expression levels in Sirt1 null mutants restores ethanol tolerance, demonstrating that both induction and termination of Hr38 expression are important for behavioral plasticity to proceed. These data demonstrate that Hr38 functions as an immediate early transcription factor that promotes ethanol behavioral plasticity.

neuroscience↗