Biology subjects

Munch, D.

Publications and source records attributed to Munch, D..

5 recordsLinked to original sources

bioRxiv2024

Lack of Single Amino Acids Transcriptionally Remodels Sensory Systems to Enhance the Intake of Protein and Microbiota

Adequate intake of dietary essential amino acids (eAAs) is vital for protein synthesis and metabolism. Any single eAA deprivation is sufficient to increase protein intake in Drosophila melanogaster. How such nutritional "needs" are transformed into behavioral "wants" remains poorly understood. We derived transcriptomes from the heads of flies deprived of individual eAAs to identify mechanisms by which this is achieved. We found that, while specific eAA deprivations have unique effects on gene expression, a large set of changes are shared across deprivations. We show that Or92a upregulation upon eAA deprivation increases the exploitation of yeast, the main protein source of flies. Furthermore, Ir76a upregulation was crucial for feeding on Lactobacillus, a gut bacterium that ameliorates the fitness of eAA-deprived flies. Our work uncovers common and unique transcriptional changes induced by individual eAA deprivations in an animal and reveals novel mechanisms underlying the organisms behavioral and physiological response to eAA challenges.

neuroscience↗

bioRxiv2023

A neuronal substrate for translating nutrient state and resource density estimations into foraging decisions

Foraging animals must balance the costs of exploring their surroundings with the potential benefits of finding nutritional resources. Each time an animal encounters a food source it must decide whether to initiate feeding or continue searching for potentially better options. Experimental evidence and patch foraging models predict that this decision depends on both nutritional state and the density of available resources in the environment. How the brain integrates such internal and external states to adapt the so-called exploration-exploitation trade-off remains poorly understood. We use video-based tracking to show that Drosophila regulates the decision to engage with food patches based on nutritional state and travel time between food patches, the latter being a measure of food patch density in the environment. To uncover the neuronal basis of this decision process, we performed a neurogenetic silencing screen of more than 400 genetic driver lines with sparse expression patterns in the fly brain. We identified a population of neurons in the central complex that acts as a key regulator of the decision to engage with a food patch. We show that manipulating the activity of these neurons alters the probability to engage, that their activity is modulated by the protein state of the animal, and that silencing these neurons perturbs the ability of the animal to adjust foraging decisions to the flys travel time between food patches. Taken together, our results reveal a neuronal substrate that integrates nutritional state and patch density information to control a specific foraging decision, and therefore provide an important step towards a mechanistic explanation of the cognitive computations that resolve complex cost-benefit trade-offs.

neuroscience↗

bioRxiv2021

Nuclear Translocation of Vitellogenin in the Honey Bee (Apis mellifera)

Vitellogenin (Vg) is a conserved protein used by nearly all oviparous animals to produce eggs. It is also pleiotropic and performs functions in oxidative stress resistance, immunity, and, in honey bees, behavioral development of the worker caste. It has remained enigmatic how Vg affects multiple traits. Here, we asked whether Vg enters the nucleus and acts via DNA-binding. We used immunohistology, cell fractionation and cell culturation to show that a structural subunit of honey bee Vg translocates into cell nuclei. We then demonstrated Vg-DNA binding theoretically and empirically with prediction software and chromatin immunoprecipitation with sequencing (ChIP-seq), finding binding sites at genes influencing immunity and behavior. Finally, we investigated the immunological and enzymatic conditions affecting Vg cleavage and nuclear translocation, and constructed a 3D structural model. Our data are the first to show Vg in the nucleus and suggests a new fundamental regulatory role for this ubiquitous protein.

molecular biology↗

bioRxiv2018

The pentaglycine bridges of Staphylococcus aureus peptidoglycan are essential for cell integrity

Bacterial cells are surrounded by cell wall, whose main component is peptidoglycan (PG), a macromolecule that withstands the internal turgor of the cell. PG composition can vary considerably between species. The Gram-positive pathogen Staphylococcus aureus possesses highly crosslinked PG due to the presence of cross bridges containing five glycines, which are synthesised by the FemXAB protein family. FemX adds the first glycine of the cross bridge, while FemA and FemB add the second and the third, and the fourth and the fifth glycines, respectively. Of these, FemX was reported to be essential. To investigate the essentiality of FemAB, we constructed a conditional S. aureus mutant of the femAB operon. Depletion of femAB was lethal, with cells appearing as pseudomulticellular forms that eventually lyse due to extensive membrane rupture. This deleterious effect was mitigated by drastically increasing the osmolarity of the medium, indicating that pentaglycine crosslinks are required for S. aureus cells to withstand internal turgor. Despite the absence of canonical membrane targeting domains, FemA has been shown to localise at the membrane. To study its mechanism of localisation, we constructed mutants in key residues present in the putative transferase pocket and the 6 helix of FemA, possibly involved in tRNA binding. Mutations in the 6 helix led to a sharp decrease in protein activity in vivo and in vitro but did not impair correct membrane localisation, indicating that FemA activity is not required for localisation. Our data indicates that, contrarily to what was previously thought, S. aureus cells do not survive in the absence of a pentaglycine cross bridge.

microbiology↗

bioRxiv2017

Organ-Specific NLR Resistance Gene Expression Varies With Plant Symbiotic Status

Nucleotide-binding site leucine-rich repeat resistance genes (NLRs) allow plants to detect microbial effectors. We hypothesized that NLR expression patterns would reflect organ-specific differences in effector challenge and tested this by carrying out a meta-analysis of expression data for 1,235 NLRs from 9 plant species. We found stable NLR root/shoot expression ratios within species, suggesting organ-specific hardwiring of NLR expression patterns in anticipation of distinct challenges. Most monocot and dicot plant species preferentially expressed NLRs in roots. In contrast, Brassicaceae species, including oilseed rape and the model plant Arabidopsis thaliana, were unique in showing NLR expression skewed towards the shoot across multiple phylogenetically distinct groups of NLRs. The Brassicaceae NLR expression shift coincides with loss of the endomycorrhization pathway, which enables intracellular root infection by symbionts. We propose that its loss offer two likely explanations for the unusual Brassicaceae NLR expression pattern: loss of NLR-guarded symbiotic components and elimination of constraints on general root defences associated with exempting symbionts from targeting. This hypothesis is consistent with the existence of Brassicaceae-specific receptors for conserved microbial molecules and suggests that Brassicaceae species are rich sources of unique antimicrobial root defences.

plant biology↗