Biology subjects

Ebel, C.

Publications and source records attributed to Ebel, C..

3 recordsLinked to original sources

bioRxiv2026

Integrated phenomic and transcriptomic analyses unveil superior drought plasticity of North African durum wheat landraces

Drought is a major constraint on the productivity of durum wheat across Mediterranean and North African regions. To elucidate the mechanisms underlying drought resilience, we employed a combination of scenario-controlled phenomics and flag leaf transcriptomics across ten durum wheat genotypes. These included the Tunisian landraces Chili and Mahmoudi, seven breeding lines, and the reference cultivar Svevo. The plants were grown to maturity under well-watered or long-term drought conditions in pots and rhizotrons, enabling a comprehensive assessment of growth, yield components, root architecture, physiological traits, and reaction norm plasticity. Drought markedly reduced performance, yet Chili and Mahmoudi consistently maintained superior biomass, grain number and intrinsic water use efficiency (iWUE). This was supported by balanced C/N allocation, strong osmotic adjustment, and the ability to sustain robust root systems under stress, albeit through partly divergent physiological strategies. Transcriptomic profiling revealed highly genotype specific responses, with drought tolerance unrelated to the number of differentially expressed genes. Instead, the landraces displayed distinct regulatory programs involving mainly photosynthesis protection, ABA-related transporters, osmotic adjustment pathways, and stress-responsive transcription factors. These mechanistic insights identify actionable physiological and molecular determinants of drought plasticity and provide high value targets for accelerating the breeding of climate resilient durum wheat. HighlightsIntegrated phenomics and transcriptomics revealed landrace-specific physiological and molecular mechanisms enabling superior drought resilience and identifying actionable targets for durum wheat improvement.

plant biology↗

bioRxiv2025

Analytical Ultracentrifugation as a Tool for Exploring COSAN Assemblies.

The self-assembly of the cobalta bis(dicarbollide) (COSAN) anionic boron clusters into micelles above a critical micelle concentration (cmc) of 10 - 20 mM and its behavior as "sticky nano-ions" facilitating controlled protein aggregation have been previously investigated using scattering techniques, particularly small-angle neutron and X-ray scattering. These techniques effectively provide average structural parameters but, when applied to colloidal systems, often rely on models assuming polydispersity or anisotropic shapes. Thus, complementary techniques are required to confirm or infirm the proposed analyses. Here, we employed sedimentation velocity analytical ultracentrifugation (SV-AUC), which offers the ability to resolve discrete species. We revisited two key questions: (1) the aggregation behavior of COSAN into micelles, a topic still under debate and due to its unconventional amphiphilic nature, and (2) the nature of the protein assemblies induced by COSAN, specifically their size/shape distribution and aggregation number. Our findings confirm the cmc of COSAN of 16 mM and reveal that COSAN micelles exhibit low aggregation numbers (8 in water and 14 in dilute salt), consistent with recent hypotheses. Furthermore, SV-AUC showed that COSAN promotes myoglobin aggregation into discrete oligomeric species with well-defined aggregation numbers, such as dimers, tetramers, and higher-order assemblies, depending on the COSAN-to-protein ratio. These results provide clarity on the discrete nature of COSAN micelle aggregation and protein assembly. This study highlights the complementary role of SV-AUC in understanding supramolecular assemblies, offering useful insights into the behavior of COSAN nano-ions and their interactions with biomacromolecules.

biophysics↗

bioRxiv2018

Interplay of protein disorder in retinoic acid receptor heterodimer and its corepressor regulates gene expression

The retinoic acid receptors (RARs) form heterodimers with retinoid X receptors (RXRs) and control gene transcription in response to ligand binding and via allosteric activation of the C-termini helix (helix H12) of its ligand-binding domain. Herein we show that in the absence of ligand, helices H12 of RXR and RAR are disordered. The selective RAR agonist, Am580, induces folding of H12, whereas in the presence of the inverse agonist BMS493, H12 stays mostly disordered. These results substantiate a link between the structural dynamics of H12 and RXR/RAR heterodimer biological functions, and highlight disordered-to-order transition as an essential mechanism for retinoic acid mediated regulation. Unliganded RAR exerts a strong repressive activity allowed by the recruitment of transcriptional corepressors and establishment of a corepressor complex in the promoter region of target genes. The human regulatory complex of the RAR bound to the full-length interaction domain of the corepressor N-CoR was studied by integrating several experimental (SAXS, X-ray crystallography, NMR, CD, AUC) and computational data. Unexpectedly, we found that, while mainly intrinsically disordered, the N-CoR presents partially evolutionary conserved structured regions that are involved in transient intramolecular contacts. In the presence of RXR/RAR, we show that N-CoR exploits its multivalency to form a multi-site complex that diplays an equilibrium between different conformational states. This conformational equilibrium is modulated by cognate ligands, RAR point mutation and RXR H12 deletion. Now, we can state that, in addition to NR conformation and ligand-induced allosteric changes, intrinsic disorder is substantially embedded in the synergetic regulation of RXR/RAR activity and its resulting abilities to communicate with the intracellular components.

biophysics↗