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Eugene, M.

Publications and source records attributed to Eugene, M..

2 recordsLinked to original sources
bioRxiv2026

Characterisation of the new microalgal protein xATPA related to the F-type ATP synthase α subunit, from the ecosystem to the molecule

Microalgal metabolism relies on their chloroplasts, and involves both nucleus and plastidial-encoded proteins of various evolutionary origins. The plastidial ATP synthase complex is a key player in photosynthesis, and has been extensively studied in plants. However, our knowledge in other photosynthetic eukaryotes remains limited, despite their importance in marine environments. Here, we report the characterisation of a novel homologue of the F-type ATP synthase alpha subunit, hereby named xATPA, widespread in microalgae but absent from other photosynthetic organisms. Comparisons of xATPA sequences and predicted structures revealed a specific feature, the bump domain, and highlighted the absence of an ATP-binding site. We assessed xATPA prevalence in microalgae in the global ocean using environmental data from Tara Oceans, with a particular focus on diatoms, and demonstrate that its expression is associated with polar summer conditions. Using a reverse genetic approach in the model diatom Phaeodactylum tricornutum, we show that xATPAPt has a plastidial localisation, and that xATPA KO mutants exhibit growth deficiencies in a combination of low temperature, low salinity and constant light, consistent with environmental analysis. Surprisingly, both RNAseq and physiological assays suggest that xATPA is not involved in ATP synthase functions. On the other hand, xATPA interacts with other F1 ATP synthase subunits in vitro, which we suggest forms transient unassembled complexes. This study hence represents a comprehensive analysis of a novel protein from the environment to the lab, and reveals a new player in the plastidial physiology of eukaryotic microalgae.

plant biology↗
bioRxiv2024

Dynamic sensitivity analysis of a mathematical model describing the effect of the macroalgae *Asparagopsis taxiformis* on rumen fermentation and methane production under *in vitro* continuous conditions

Ruminants play an important role in global warming by emitting enteric methane (CH4) through the degradation of feeds by the rumen microbiota. To better understand the dynamics fermentation outputs, including CH4 and volatile fatty acids (VFA) production, mathematical models have been developed. Sensitivity analysis (SA) methods quantify the contribution of model input parameters (IP) to the variation of an output variable of interest. In animal science, SA are usually conducted in static condition. In this work, we hypothesized that including the dynamic aspect of the rumen fermentation to SA can be useful to inform on optimal experimental conditions aimed at quantifying the key mechanisms driving CH4 and VFA production. Accordingly, the objective of this work was to conduct a dynamic SA of a rumen fermentation model under in vitro continuous conditions (close to the real in vivo conditions). Our model case study integrates the effect of the macroalgae Asparagopsis taxiformis (AT) on the fermentation. AT has been identified as a potent CH4 inhibitor via the presence of bromoform, an anti-methanogenic compound. We computed Shapley effects over time for quantifying the contribution of 16 IPs to CH4 (mol/h) and VFA (mol/l) variation. Shapley effects integrate the three contribution types of an IP to output variable variation (individual, via the interactions and via the dependence/correlation). We studied three diet scenarios accounting for several doses of AT relative to Dry Matter (DM): control (0% DM of AT), low treatment (LT: 0.25% DM of AT) and high treatment (HT: 0.50% DM of AT). Shapley effects revealed that hydrogen (H2) utilizers microbial group via its Monod H2 affinity constant highly contributed (> 50%) to CH4 variation with a constant dynamic over time for control and LT. A shift on the impact of microbial pathways driving CH4 variation was revealed for HT. IPs associated with the kinetic of bromoform utilization and with the factor modeling the direct effect of bromoform on methanogenesis were identified as influential on CH4 variation in the middle of fermentation. Whereas, VFA variation for the three diet scenarios was mainly explained by the kinetic of fibers degradation, showing a high constant contribution (> 30%) over time. The simulations computed for the SA were also used to analyze prediction uncertainty. It was related to the dynamic of dry matter intake (DMI, g/h), increasing during the high intake activity periods and decreasing when the intake activity was low. Moreover, CH4 (mol/h) simulations showed a larger variability than VFA simulations, suggesting that the reduction of the uncertainty of IPs describing the activity of the H2 utilizers microbial group is a promising lead to reduce the overall model uncertainty. Our results highlighted the dynamic nature of the influence of metabolic pathways on CH4 productions under an anti-methanogenic treatment. SA tools can be further exploited to design optimal experiments studying rumen fermentation and CH4 mitigation strategies. These optimal experiments would be useful to build robust models that can guide the development of sustainable nutrition strategies.

systems biology↗