Biology subjects

Kuhn, M.-L.

Publications and source records attributed to Kuhn, M.-L..

3 recordsLinked to original sources

bioRxiv2026

Zoospore-derived extracellular vesicles in the flagellated stramenopile Phytophthora parasitica

Zoospores are unicellular, wall-less and flagellated cells produced by a number of eukaryotic microorganisms. They allow microbial dispersion, enable the search and location for new sources of nutrients where they aggregate, initiate pathogen-host interactions and communication within microbiota. Little is known about their ability to release bioactive extracellular vesicles (EVs) supporting these adaptations. Here we used electron microscopy to establish that in the biflagellate zoospores of the heterokont and phytopathogenic species Phytophthora parasitica, EV biogenesis occurs from vesicles budding either at cell body plasma membrane or at the front flagellum, in particular from the tubular mastigonemes. Zoospore-conditioned water supernatant was fractionated and characterized by means of morphological, immunochemical, proteomic and lipidomic analyses. Three fractions enriched in cell body, flagella and EVs were obtained by differential ultracentrifugation at 3,000g, 31,000g and 100,000g, respectively, with the EV fraction consisting of small vesicles (100-150 nm). Using mass spectrometry, label-free proteomic analysis of the EV fraction (1,470 proteins) revealed a collection of proteins involved in lipid transport, vesicle membrane and cell wall organization, and tubular mastigoneme architecture, but not in virulence. Label-free quantitative lipidomic analysis (191 lipids) revealed enrichment of EVs in sphingolipids, particularly ceramides compared with the cell body. These findings provide a first hallmark of features characteristic of zoosporic EVs, with ceramides, mastigoneme proteins and the EV-related protein PPTG_13069 containing two tetraspanin MARVELous domains among molecular markers. They define the molecular and cellular principles in understanding zoosporic EV biogenesis within Stramenopiles and intercellular communication between self-aggregating zoospores, with host plant cells or microbiota.

molecular biology↗

bioRxiv2025

Contractile Vacuole and Papilla drive Cyst/Telotroch transition in Vorticella microstoma

The cyst of the protist ciliate Vorticella efficiently differentiates into teletroch, the free-swimming stage. Here, using video microscopy and quantitative imaging we establish that the cyst differentiation follows two strict temporal and spatial patterns. The temporal pattern is initially marked by the functional formation of the contractile vacuole, which then discharges its fluid into the neoformed cytopharynx and, in a third stage, into a membrane invagination which, to the rhythm of the vacuole, differentiates into an oral cavity exhibiting a polarized cilia array revealed by -tubulin immunostaining. Two poles delineate the spatial pattern. The apical pole is defined by the position of the pre-existing papilla, which determines the site of oral cavity formation directly below it. The second basal pole is placed at the rupture point of the cyst wall. It is characterized by {beta}-actin accumulation and allowed release of the telotroph according to its basal-apical polarity. Both the temporal and spatial patterns are impaired by concanamycin A treatment, a specific inhibitor of vacuolar type H+-ATPases altering functions of contractile vacuoles. The findings indicate that cyst to telotroch transition is predetermined by the location of the papilla on the cyst wall and under the control of a functional contractile vacuole. We propose that Vorticella cyst is a simple single-cell model for investigating basic principles of integrative neogenesis of organelles in Protozoa, and of apical-basal cell polarity in Eukaryotes.

microbiology↗

bioRxiv2019

An oomycete effector impairs autophagy in evolutionary distant organisms and favors host infection

An arsenal of effector proteins from plant pathogenic Phytophthora species manipulates their host from inside the cells. Phytophthora parasitica produces the effector AVH195 during an initial, biotrophic phase of infection. The protein transiently impairs plant immune-associated hypersensitive cell death in Nicotiana. ATG8 Interaction Motifs in the protein indicate that the effector targets the autophagic core machinery. We selected a photosynthetic microalga with a single copy ATG8 gene as an alternative model to dissect AVH195-induced autophagic perturbation. AVH195 slows down autophagic flux in Chlamydomonas reinhardtii thus promoting the accumulation of cargo-rich vesicles. In yeast, membrane-associated AVH195 interacts with ATG8 from Chlamydomonas and with different ATG8 isoforms from Arabidopsis thaliana. The overexpression of Avh195 in Arabidopsis promotes growth of both infecting P. parasitica and Hyaloperonospora arabidopsidis, an obligate biotroph. To our knowledge, this report provides first evidence that an oomycete effector non-selectively targets ATG8 in different organisms from the green lineage to slow down autophagic flux for infection.

plant biology↗