Biology subjects

Gillet, F.-X.

Publications and source records attributed to Gillet, F.-X..

6 recordsLinked to original sources

bioRxiv2026

A miniaturized Arabidopsis thaliana - Botrytis cinerea seedling pathosystem and the GreenDayz workflow for longitudinal image-based phenotyping

Plant-pathogen interactions are strongly influenced by host developmental stage, yet many Arabidopsis thaliana-Botrytis cinerea assays remain centred on mature rosette leaves and rely on inoculum loads that may exceed those involved in a primary infection. We established a miniaturized in vitro A. thaliana-B. cinerea seedling pathosystem initiated with a very low conidial dose (nominally ~25 conidia per plate) compatible with both destructive molecular sampling and repeated, non-destructive RGB imaging. The pathosystem was coupled to a low-cost smartphone photo station and to GreenDayZ Phenotyping, a guided image-analysis application with an intuitive graphical interface that standardizes longitudinal RGB image processing and extracts quantitative colour-based phenotypes. Together, the pathosystem and GreenDayZ Phenotyping provide an accessible and reproducible framework for longitudinal phenotyping of low-inoculum seedling infections, in which image-derived trajectories can be aligned with independent molecular readouts.

pathology↗

bioRxiv2026

Asymptomatic colonization by Botrytis cinerea reveals polarized plant-fungus interfaces before widespread disease

Botrytis cinerea is a necrotrophic pathogen whose destructive growth is typically studied under conditions that rapidly generate visible disease. Yet symptomless associations are well documented, the fungal and host processes operating before widespread tissue collapse remain poorly resolved. We developped an intact Arabidopsis thaliana seedling pathosystem that extends the interval between infection establishment and widespread visible disease. Fungal colonization was quantified using qPCR and a constitutively bioluminescent reporter strain, together with longitudinal plant phenotyping, hormone profiling and multiscale fluorescence microscopy. Substantial fungal colonization occurred while seedlings remained largely green and continued to grow, whereas robust whole seedling accumulation of salicylic and jasmonic acids occurred later. During this interval, B. cinerea displayed diverse tissue-associated infection morphologies. At individual contact sites, fungal walls showed heterogeneous exposure of chitin-associated epitopes, while host cells exhibited focal plasma-membrane polarization toward fungal contact sites, together with cortical actin reorganization. These results show that the interval preceding widespread visible disease is an active and spatially heterogeneous interaction state, in which substantial fungal development and highly organized local host responses are already established. Intact seedlings therefore provide a powerful system for resolving plant-pathogen interactions that are largely obscured in rapid disease assays.

pathology↗

bioRxiv2026

Multifaceted roles of extracellular vesicles in Agrobacterium fabrum C58 lifestyles

Bacterial extracellular vesicles (EVs) constitute a key driver of interspecies and inter-kingdom communication, and shape bacterial ecology, yet their role as a dynamic delivery system remains underexplored. Here, we show that the plant pathogen Agrobacterium fabrum C58 modulates its EVs in response to virulence-inducing conditions. Our multi-omics analysis revealed that these virulence-state EVs are significantly enriched in effectors from the Type IV secretion system and toxins from the Type VI secretion system, which were previously known to be delivered by conventional contact-dependent mechanisms. We demonstrate that these EVs can directly transfer virulence effectors into plant host cells, enhancing tumor formation. Furthermore, we show that these EVs can interact with and influence the development of several environmental bacteria. Finally, A. fabrum C58 EVs elicit distinct plant host metabolome responses compared to whole cells. Our findings establish EVs as a crucial and dynamic component of bacterial virulence and inter-kingdom communication, providing a new perspective on how bacteria adapt to and manipulate their environment.

microbiology↗

bioRxiv2024

The plastid-encoded RNA polymerase structures a logistic chain for light-induced photosynthesis

The chloroplast is the semi-autonomous organelle of eukaryotes that performs photosynthesis. In higher plants, chloroplast biogenesis depends on a tight transcriptional coordination of both nuclear- and-plastid photosynthesis-associated genes. The plastid-encoded RNA-polymerase (PEP) is composed of a plastid-encoded catalytic core, similar to multi-subunit RNA polymerases, bound to fifteen nuclear-encoded PEP-associated proteins (PAPs). The binding of all the PAPs to the catalytic core is essential for plastid transcription of photosynthesis-associated genes. Our cryo-electron microscopy structure of the native 21-subunit PEP from Sinapis alba reveals the distinctive patterning of PAP interactions, which evolved upon the ancestral cyanobacterial catalytic core acting as a scaffold. Using PAP8 in planta as bait for affinity purification and proximity labeling, we provide the protein landscapes surrounding the PEP and other PAP8-interacting complexes at the transition from skotomorphogenesis to photomorphogenesis. The data highlight multiple functional couplings in which plastid transcription is at the beginning of a spatial logistic chain, extending from transcription to the assembly of the photosynthetic apparatus into the thylakoids. In addition, dark-specific interactions between photoreceptors and PAP8 establish a physical link between an integrated light signaling and plastid functions.

plant biology↗

bioRxiv2022

Three-dimensional envelope and subunit interactions of the plastid-encoded RNA polymerase from Sinapis alba

RNA polymerases (RNAPs) involved in gene transcription are found in all living organisms with degrees of complexity ranging from single polypeptide chains to multimeric enzymes. In the chloroplasts, the nuclear-encoded RNA polymerase and the plastid-encoded RNA polymerase (PEP) are both involved in the selective transcription of the plastid genome. The PEP is a prokaryotic-type multimeric RNAP found in different states depending on light stimuli and cell identity. One of its active states requires the assembly of nuclear-encoded PEP-Associated Proteins (PAPs) on the catalytic core, producing a complex of more than 900 kDa regarded as essential for chloroplast biogenesis. A purification procedure compatible with structural analysis was used to enrich the native PEP from Sinapis alba chloroplasts. Mass spectrometry (MS)-based proteomic analysis identified the core components, the PAPs and additional members, and coupled to cross-linking (XL-MS) provided initial structural information about the relative position of PEP subunits. Sequence alignments of the catalytic core subunits across various chloroplasts of the green lineage and prokaryotes combined with structural data show that the overall shape of the catalytic core and the residues essential for the catalytic activity are conserved. However, variations are observed at the surface of the core, some of them corresponding to PAP binding sites as suggested by XL-MS experiments. Using negative stain electron microscopy, the PEP 3D envelope was calculated. 3D classification shows that the protrusions which we attribute to the PAPs are firmly associated with the catalytic core. Overall, the shape of the S. alba PEP envelope is different from that of RNAPs.

biochemistry↗

bioRxiv2020

Nucleo-plastidic PAP8/pTAC6 couples chloroplast formation with photomorphogenesis

The initial greening of angiosperm occurs upon light-activation of photoreceptors that trigger photomorphogenesis followed with the development of chloroplasts. In these semi-autonomous organelles, the construction of the photosynthetic apparatus depends on the coordination of nuclear and plastid gene expression. Here we show that PAP8, as an essential subunit of the plastid-encoded RNA polymerase, is under the control of a regulatory element recognized by the photomorphogenic factor HY5. PAP8 is localized and active in both plastids and the nucleus and particularly essential for the formation of late photobodies. In the albino pap8 mutant, phytochrome-mediated signalling is altered, PIFs are maintained, HY5 is not stabilized, and GLK1 expression is impaired. PAP8 translocates into plastids losing its pre-sequence, interacts with the PEP, and using an unknown route or a retrograde transport, reaches the nucleus where it has the ability to interact with pTAC12/HMR/PAP5. Since PAP8 is required for the phytochrome-B-mediated signalling cascade and the reshaping of the PEP, it may coordinate nuclear gene expression with the PEP-driven chloroplastic gene expression during chloroplast biogenesis.

plant biology↗