Biology subjects

Templin, R.

Publications and source records attributed to Templin, R..

7 recordsLinked to original sources

bioRxiv2024

Life Cycle and Morphogenetic Differentiation in Heteromorphic Cell Types of a Cosmopolitan Marine Microalga

O_LIGephyrocapsa huxleyi is a prevalent, bloom-forming phytoplankton species in the oceans. It exhibits a complex haplo-diplontic life cycle, featuring a diploid-calcified phase, a haploid phase, and a third decoupled phase produced during viral infection. Decoupled cells display a haploid-like phenotype, but are diploid. C_LIO_LIHere, we investigated the fate of decoupled cells during culture observations and we compared the transcriptome profiles and the cellular ultrastructure of the three cell types. C_LIO_LIWe found that decoupled cells can revert to the calcified form in the absence of viral pressure, revealing the transient nature of this cell type. Ultrastructural analyses showed distinct nuclear organisation with variations in chromatin volume. Transcriptomic analyses revealed gene expression patterns specific to each life phase. These included multiple regulatory functions in chromatin remodelling, broader epigenetic mechanisms and life cycling, which likely contributed to cell differentiation. Finally, the exploration of available host-virus transcriptomes supports life cycle transition during viral infection. C_LIO_LIThis study provides cellular and molecular foundations for nuclear remodelling and cell differentiation in coccolithophores and the identification of gene markers for studying coccolithophore life cycles in natural populations. C_LI

plant biology↗

bioRxiv2023

Antiviral Wolbachia strains associate with Aedes aegypti endoplasmic reticulum membranes and disturb host cell lipid distribution to restrict dengue virus replication.

The insect endosymbiotic bacterium Wolbachia pipientis is being utilised as a biocontrol tool to reduce the incidence of Aedes aegypti-transmitted viral diseases like dengue. However, the precise mechanisms underpinning Wolbachias antiviral activity are not well defined. Here we generated a panel of Ae. aegypti-derived cell lines infected with antiviral strains wMel and wAlbB or the non-antiviral strain wPip to understand host cell morphological changes specifically induced by antiviral strains. Antiviral strains were frequently found to be entirely wrapped by the host endoplasmic reticulum (ER) membrane, while wPip bacteria clustered separately in the host cell cytoplasm. ER-derived lipid droplets (LDs) increased in volume in wMel-and wAlbB-infected cell lines and mosquito tissues compared to cells infected with wPip or Wolbachia-free controls. Inhibition of fatty acid synthase (required for triacylglycerol biosynthesis) reduced LD formation and significantly restored ER-associated dengue virus replication in cells occupied by wMel. Together, this suggests that antiviral Wolbachia strains may specifically alter the lipid composition of the ER to preclude the establishment of DENV replication complexes. Defining Wolbachias antiviral mechanisms will support the application and longevity of this effective biocontrol tool that is already being used at scale. ImportanceAedes aegypti transmits a range of important human pathogenic viruses like dengue. However, infection of Ae. aegypti with the insect endosymbiotic bacterium, Wolbachia, reduces the risk of mosquito to human viral transmission. Wolbachia is being utilized at field sites across more than 13 countries to reduce the incidence of viruses like dengue, but it is not well understood how Wolbachia induces its antiviral effects. To examine this at the subcellular level, we compared how different strains of Wolbachia with varying antiviral strengths, associate with and modify host cell structures. Strongly antiviral strains were found to specifically associate with the host endoplasmic reticulum and induce striking impacts on host cell lipid distribution. Inhibiting Wolbachia-induced lipid redistribution partially restored dengue virus replication demonstrating this is a contributing role for Wolbachias antiviral activity. These findings provide new insights into how antiviral Wolbachia strains associate with and modify Ae. aegypti host cells.

microbiology↗

bioRxiv2022

Crosshair, semi-automated targeting for electron microscopy with a motorised ultramicrotome

Volume electron microscopy (EM) is a time consuming process - often requiring weeks or months of continuous acquisition for large samples. In order to compare the ultrastructure of a number of individuals or conditions, acquisition times must therefore be reduced. For resin-embedded samples, one solution is to selectively target smaller regions of interest by trimming with an ultramicrotome. This is a difficult and labour-intensive process, requiring manual positioning of the diamond knife and sample, and much time and training to master. Here, we have developed a semi-automated workflow for targeting with a modified ultramicrotome. We adapted two recent commercial systems to add motors for each rotational axis (and also each translational axis for one system), allowing precise and automated movement. We also developed a user-friendly software to convert X-ray images of resin-embedded samples into angles and cutting depths for the ultramicrotome. This is provided as an open-source Fiji plugin called Crosshair. This workflow is demonstrated by targeting regions of interest in a series of Platynereis dumerilii samples.

cell biology↗

bioRxiv2021

Intracellular development and impact of a eukaryotic parasite on its zombified microalgal host in the marine plankton

Parasites are widespread and diverse in the oceanic plankton, and many of them infect single-celled algae for survival. How these parasites develop and scavenge energy within the host and whether the cellular organization and metabolism of the host is altered remain open questions. Combining quantitative structural and chemical imaging with time-resolved transcriptomics, we unveil dramatic morphological and metabolic changes of the parasite Amoebophrya (Syndiniales) during intracellular infection (e.g. 200-fold increase of mitochondrion volume), particularly following digestion of nutrient-rich host chromosomes. Some of these changes are also found in the apicomplexan parasites (e.g. sequential acristate and cristate mitochondrion, switch from glycolysis to TCA), thus underlining key evolutionary-conserved mechanisms. In the algal host, energy-producing organelles (chloroplast) remain intact during most of the infection, but sugar reserves diminish while lipid droplets increase. Thus, rapid infection of the host nucleus could be a zombifying strategy to digest nutrient-rich chromosomes and escape cytoplasmic defense while benefiting from the maintained C-energy production of the host cell.

cell biology↗

bioRxiv2020

In-cell quantitative structural imaging of phytoplankton using 3D electron microscopy

Phytoplankton is a minor fraction of the global biomass playing a major role in primary production and climate. Despite improved understanding of phytoplankton diversity and genomics, we lack nanoscale subcellular imaging approaches to understand their physiology and cell biology. Here, we present a complete Focused Ion Beam - Scanning Electron Microscopy (FIB-SEM) workflow (from sample preparation to image processing) to generate nanometric 3D phytoplankton models. Tomograms of entire cells, representatives of six ecologically-successful phytoplankton unicellular eukaryotes, were used for quantitative morphometric analysis. Besides lineage-specific cellular architectures, we observed common features related to cellular energy management: i) conserved cell-volume fractions occupied by the different organelles; ii) consistent plastid-mitochondria interactions, iii) constant volumetric ratios in these energy-producing organelles. We revealed detailed subcellular features related to chromatin organization and to biomineralization. Overall, this approach opens new perspectives to study phytoplankton acclimation responses to abiotic and biotic factors at a relevant biological scale.

plant biology↗

bioRxiv2020

Whole-body integration of gene expression and single-cell morphology

Animal bodies are composed of hundreds of cell types that differ in location, morphology, cytoarchitecture, and physiology. This is reflected by cell type-specific transcription factors and downstream effector genes implementing functional specialisation. Here, we establish and explore the link between cell type-specific gene expression and subcellular morphology for the entire body of the marine annelid Platynereis dumerilii. For this, we registered a whole-body cellular expression atlas to a high-resolution electron microscopy dataset, automatically segmented all cell somata and nuclei, and clustered the cells according to gene expression or morphological parameters. We show that collective gene expression most efficiently identifies spatially coherent groups of cells that match anatomical boundaries, which indicates that combinations of regionally expressed transcription factors specify tissue identity. We provide an integrated browser as a Fiji plugin to readily explore, analyse and visualise multimodal datasets with remote on-demand access to all available datasets.

cell biology↗

bioRxiv2019

Caveolae set levels of epithelial monolayer tension to eliminate tumor cells

Mechanical tension governs epithelial morphogenesis and homeostasis, but its regulation remains poorly understood. Tension is commonly contractile, arising when the actomyosin cortices of cells are mechanically coupled together by cadherin adhesion. Here we report that caveolae control levels of epithelial tension and show that this is necessary for oncogene-transfected cells to be eliminated by apical extrusion. Depletion of caveolin-1 (CAV1) in the surrounding epithelium, but not in the oncogene-expressing cells, blocked extrusion leading to the retention and proliferation of transformed cells within the monolayer. Tensile stress was aberrantly elevated in CAV1-depleted monolayers due to elevated levels of phosphoinositide-4,5-bisphosphate (PtdIns(4,5)P2) causing increased recruitment of the formin, FMNL2. Oncogenic extrusion was restored to CAV1-deficient monolayers when tension was corrected by depleting FMNL2, blocking PtdIns(4,5)P2, or disabling the interaction between FMNL2 and PtdIns(4,5)P2. Thus, by controlling lipid signalling to the actin cytoskeleton, caveolae regulate mechanical tension for epithelial homeostasis.

cell biology↗