Biology subjects

Bagchi, B.

Publications and source records attributed to Bagchi, B..

4 recordsLinked to original sources

bioRxiv2026

Temperature-sensitive cytoplasmic incompatibility across divergent Wolbachia partly reflects cifB transcription, not endosymbiont density

Maternally transmitted Wolbachia bacteria are common in insects, with many strains altering host reproduction through cytoplasmic incompatibility (CI). CI kills embryos fertilized by Wolbachia-bearing males unless those embryos also carry Wolbachia, which favors females with Wolbachia and drives the endosymbiont to higher frequencies in host populations. Strong CI now underpins successful applications that rely on maintaining pathogen-blocking Wolbachia transinfections in vector populations to reduce arboviral disease transmission. Temperature modulates CI strength (the proportion of embryos killed), with consequences for Wolbachia prevalence in natural and transinfected populations. Yet the mechanisms regulating temperature-sensitive CI-strength variation are poorly understood. We quantified CI strength across eight divergent Drosophila-associated Wolbachia strains at four temperatures (18{degrees}C-26{degrees}C), while characterizing development time, Wolbachia and Wovirus densities, and transcription of the CI-inducing gene cifB. Four of eight Wolbachia strains exhibited temperature-sensitive CI, three of which induced CI at multiple temperatures. Of these three, two expressed significantly more cifB at the temperature yielding stronger CI, whereas testes Wolbachia density did not predict CI strength. Notably, cifB-transcript levels were consistently decoupled from Wolbachia and Wovirus densities, suggesting that cifB transcription is not regulated solely by symbiont abundance. We also report temperature-sensitive rescue of CI, Wolbachia-associated developmental acceleration, and strain-specific Wovirus-Wolbachia covariance. Our findings reveal temperature as a pervasive modulator of Wolbachia-host interactions at multiple levels and extend evidence that cifB transcription partly predicts variable CI strength across strain identities, male ages, and now temperatures. CI variation unaccounted for by cifB transcription points toward additional regulatory or post-transcriptional mechanisms that we discuss.

molecular biology↗

bioRxiv2022

Bimodal 1/f noise and anticorrelation between DNA-Water and DNA-Ion energy fluctuations

Coupling between the fluctuations of DNA and its surroundings consisting of water and ions in solution remains poorly understood and relatively less investigated as compared to proteins. Here, with the help of molecular dynamics simulations and statistical mechanical analyses, we explore the dynamical coupling between DNA, water, and counterions through correlations among respective energy fluctuations in both double (ds-) and single-stranded (ss-) DNA solutions. Fluctuations in the collective DNA-Water and DNA-Ion interaction energies are found to be strongly anti-correlated across all the systems. The fluctuations of DNA self-energy, however, are weakly coupled to DNA-water and DNA-ion interactions in ds-DNA. An enhancement of the DNA-water coupling is observed in ss-DNA, where the system is less rigid. All the interaction energies exhibit 1/f noise in their energy power spectra with surprisingly prominent bimodality in the DNA-water and DNA-ion fluctuations. The nature of the energy spectra appears to be indifferent to the relative rigidity of the DNA. We discuss the role of the observed correlations in ion-water motions on a DNA duplex in the experimentally observed anomalous slow dielectric relaxation and solvation dynamics, and in furthering our understanding of the DNA energy landscape. TOC GRAPHIC O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=144 SRC="FIGDIR/small/520228v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@806797org.highwire.dtl.DTLVardef@110c9corg.highwire.dtl.DTLVardef@1531566org.highwire.dtl.DTLVardef@1a1fe12_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

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

CARCASS SCAVENGING RELAXES CHEMICAL-DRIVEN FEMALE INTERFERENCE COMPETITION

Female-female nonsexual interference competition is rapidly emerging as a major fitness determinant of biased sex-ratio groups with high female density. How do females overcome such competition? We used adult flour beetle Tribolium castaneum to answer this question, where females from female-biased groups suppressed each others fecundity by secreting toxic quinones from their stink glands, revealing a chemical-driven interference competition. The added natal resource did not alleviate these fitness costs. Females also did not disperse more at high female-density. Hence, the competition was neither limited by the total resource availability nor the inability to avoid chemical interference. Instead, protein sequestered via scavenging of nutrient-rich carcasses relaxed the female competition, by increasing their fecundity and reducing the quinone content. Even infected carcasses were scavenged to extract fitness benefits, despite the infection-risk. Finally, individual stink gland components triggered carcass-scavenging to increase fecundity, indicating a potentially novel chemical feedback loop to reduce the competition.

ecology↗