Biology subjects

Degut, C.

Publications and source records attributed to Degut, C..

6 recordsLinked to original sources

bioRxiv2026

A spatial atlas of the seaweed CO2-fixation machinery reveals a unique Rubisco condensation mechanism

Seaweeds (macroalgae) are important primary producers that sustain food webs in coastal ecosystems. Most algae accelerate inorganic carbon assimilation by actively concentrating CO2 in a Rubisco-rich specialized organelle called the pyrenoid. However, the molecular composition of this pathway is unknown in seaweeds. Here, we investigated the intracellular localization of 160 proteins associated with CO2 acquisition in the green seaweed Ulva (Sea lettuce). We assign 68 proteins to different pyrenoid subdomains and identify a consensus Ulva Rubisco binding motif revealing the molecular logic of the Ulva pyrenoid. We reveal Seaweed Ulva Pyrenoid Assembly 1 (SUPA1) as the core pyrenoid assembly factor. We show that Rubisco condensation is driven by a unique mechanism: the helical folding of SUPA1 motifs upon Rubisco binding, combined with steric hindrance that halves the available Rubisco binding sites from eight to four. Our data gives an unprecedented sub-cellular spatial understanding on seaweed carbon fixation and provides insights into the evolution of this important pathway in the global carbon cycle.

cell biology↗

bioRxiv2026

Sticker number modulates pyrenoid condensate assembly to support algal fitness

The valency of intrinsically disordered proteins underpins liquid-liquid phase separation (LLPS), yet how this parameter shapes condensate function and cellular fitness remains poorly understood. Here we exploit the algal pyrenoid-a minimal, two component LLPS system-to directly link condensate properties to physiological performance. Pyrenoid assembly is driven by a disordered, multivalent Linker protein that binds Rubisco at symmetry-related surface sites, with the number of binding motifs ("stickers") varying across species. Using Chlamydomonas reinhardtii, we systematically tuned sticker number from two to nine and examined effects on Rubisco condensation, pyrenoid architecture and CO2 fixation. Three stickers were sufficient for condensation in vitro, but at least four were required for pyrenoid assembly in vivo. Cryo-electron tomography and single-molecule tracking revealed that increasing sticker number enhances Rubisco packing and mobility, while time-resolved imaging and competition assays demonstrated that sticker number governs the kinetics of pyrenoid formation and determines cellular fitness under fluctuating carbon conditions. Our findings establish sticker number as an evolutionary tuning parameter that balances condensate formation, dynamics, and function, providing a quantitative framework for linking the molecular grammar of phase separation to biological fitness.

cell biology↗

bioRxiv2025

An open-sourced 3D printable microscope with a large CNC stage

3D printed laboratory tools are a fast-developing field, and microscopes in particular have seen several high-quality projects reported in recent years. However, currently available projects for 3D printed microscopes have not been optimised for molecular biology applications. We present an open-source, 3D-printable optical microscope that has been specifically designed for affordability, ease of use, and versatility in molecular biology applications, particularly for fluorescence detection, time lapse imaging, and higher throughput scanning of microtitre plates. The microscope integrates a large computer numerically controlled (CNC) stage, allowing precise scanning of wells in standard microtiter plates, and is equipped with a Raspberry Pi HQ camera module and customizable optical components, including standard microscope objectives. The modular design allows for a range of illumination setups, such as a 3 W blue LED for basic epifluorescence, and supports additional modifications, including dark field or RGB matrix lighting. The design opens new possibilities for cheap home-built microscopes for bioscience applications that are modular and easily adaptable for specific user needs.

biophysics↗

bioRxiv2024

A promiscuous mechanism to phase separate eukaryotic carbon fixation in the green lineage

CO2 fixation is commonly limited by inefficiency of the CO2-fixing enzyme Rubisco. Eukaryotic algae concentrate and fix CO2 in phase-separated condensates called pyrenoids, which complete up to one-third of global CO2 fixation. Condensation of Rubisco in pyrenoids is dependent on interaction with disordered linker proteins that show little conservation between species. We developed a sequence-independent bioinformatic pipeline to identify linker proteins in green algae. We report the linker from Chlorella and demonstrate that it binds a conserved site on the Rubisco large subunit. We show the Chlorella linker phase separates Chlamydomonas Rubisco and that despite their separation by [~]800 million years of evolution, the Chlorella linker can support the formation of a functional pyrenoid in Chlamydomonas. This cross-species reactivity extends to plants, with the Chlorella linker able to drive condensation of some native plant Rubiscos in vitro and in planta. Our results represent an exciting frontier for pyrenoid engineering in plants, which is modelled to increase crop yields.

plant biology↗

bioRxiv2023

Fundamental steps in Minichromosome Maintenance complex assembly are conserved from archaea to eukaryotes

Minichromosome maintenance (MCM) proteins are the replicative helicase in both archaea and eukaryotes. Recent cryo-EM studies have defined key steps in the assembly pathway of the eukaryotic MCM2-7 complex and determined roles for each subunit. While archaeal MCMs are simpler in composition, we know little about how these homohexameric MCMs assemble. Investigation of archaeal MCMs has largely focussed on proteins from thermophilic organisms, which typically form robust oligomers under ambient experimental conditions, preventing dissection of their assembly pathway. Here, we describe an uncharacterised MCM from the mesophilic archaeon Mancarchaeum acidophilum (MacMCM). A 3D structure of MacMCM reveals subunit-subunit interfaces that are more similar to yeast MCM2-7 than previously studied MCMs from thermophilic archaea. We show that assembly of a MacMCM homohexamer on DNA proceeds via comparable steps to MCM2-7. These results reveal an ancient mechanism underlies assembly of the MCM complex, which is conserved from archaea to eukaryotes.

biochemistry↗

bioRxiv2020

Periscope Proteins are variable length regulators of bacterial cell surface interactions

Changes at the cell surface enable bacteria to survive in dynamic environments, such as diverse niches of the human host. Here, we reveal "Periscope Proteins" as a widespread mechanism of bacterial surface alteration mediated through protein length variation. Tandem arrays of highly similar folded domains can form an elongated rod-like structure; thus variation in the number of domains determines how far an N-terminal host ligand binding domain projects from the cell surface. Supported by newly-available long-read genome sequencing data, we propose this new class could contain over 50 distinct proteins, including those implicated in host colonisation and biofilm formation by human pathogens. In large multi-domain proteins, sequence divergence between adjacent domains appears to reduce inter-domain misfolding. Periscope Proteins break this "rule", suggesting their length variability plays an important role in regulating bacterial interactions with host surfaces, other bacteria and the immune system.

microbiology↗