Biology subjects

Touboul, D.

Publications and source records attributed to Touboul, D..

6 recordsLinked to original sources

bioRxiv2026

IRON DEFICIENCY RESHAPES THE POPLAR ROOT AND EXUDATE METABOLITE PROFILES AND DRIVES EXUDATE-MEDIATED IRON MOBILIZATION

Iron (Fe) deficiency under alkaline conditions limits Fe bioavailability and reshapes plant metabolism. We asked how Fe deficiency at pH 7.5 alters the metabolite profiles of roots and root exudates of Populus x canescens, and whether exudates mobilize Fe at high pH. Hydroponically grown plants were deprived of Fe for 20 and 27 days. Roots and exudates, collected in nutrient solution and in distilled water, were profiled by UHPLC-QTOF MS, and metabolites were annotated using MS/MS molecular networking (MetGem) and public spectral libraries. Fe deficiency caused significant global shifts in both root and exudate metabolomes. In roots, phenylpropanoids increased at 27 days (proanthocyanidins, neochlorogenic acid, naringenin), whereas the salicylate glycoside salicortin decreased, suggesting a redirection of phenylpropanoid flux. In nutrient-solution exudates, eight flavonoids, including quercitrin, accumulated strongly at 27 days, and catecholic coumarins such as fraxetin were detected in roots and exudates. Exudates from Fe-deficient plants increased Fe mobilization from Fe(III) oxides at pH 7.5, and quercitrin solubilized Fe as efficiently as fraxetin. Alkaline Fe deficiency thus reconfigures poplar root and exudate metabolomes, and exuded flavonoids, not only coumarins, may contribute to Fe mobilization at high pH.

plant biology↗

bioRxiv2026

Structure of the human KEOPS/tRNA complex and characterization of pathogenic variants responsible for the Galloway Mowat syndrome.

N6-threonyl-carbamoylation of adenosine 37 of ANN-type tRNAs (t6A) is a universal modification essential for translational accuracy and efficiency. The t6A pathway uses two sequentially acting enzymes, YRDC and OSGEP, the latter being a subunit of the multiprotein KEOPS complex. Structures of the subunits and subcomplexes of human KEOPS are known, but knowledge on the detailed interactions with tRNA is lacking. We present here the first structure of complete hKEOPS and of its complex with a substrate tRNA by cryo-electron microscopy. The CAA tail of tRNA is bound to the TPRKB subunit and the anti-codon loop is positioned at the entrance of the catalytic site of OSGEP subunit. The flexibility of the OSGEP-TP53RK interface allows hKEOPS to fit the surface of the tRNA elbow. We recently identified mutations in all genes encoding for proteins of the t6A pathway in children with Galloway-Mowat syndrome (GAMOS), a clinically heterogeneous recessive disease characterized by early-onset steroid-resistant nephrotic syndrome and microcephaly. We here expressed and characterized the majority of the Galloway Mowat mutants. All mutants could be purified at high yields and seem to be stable in vitro. The t6A activity for most of the mutants is above 40% of the WT. Using CRISPR-Cas9 technology we replaced the genes encoding the t6A pathway proteins in yeast by their human homologues. This yeast construct was perfectly viable and produced WT levels of t6A modified tRNA. Using this tool, we observed that most of the GAMOS mutants were viable in yeast and yielded comparable t6A modified tRNA levels. Our data indicate that healthy human cellular development depends on an optimized level of t6A tRNA modification and is not compatible with a total loss of function of the t6A machinery.

biochemistry↗

bioRxiv2025

Identification of the negamycin split biosynthetic gene cluster in Kitasatospora purpeofusca ATCC21470

Negamycin is a ribosome-targeting antibiotic with activity against Gram-positive and Gram-negative bacteria including ESKAPE pathogens. Furthermore, it promotes premature stop codon readthrough. Its therapeutic potential is limited by low natural production and synthetic complexity. To enable scalable biosynthesis, we identified and characterized its genetic basis in Kitasatospora purpeofusca ATCC 21470. Two distant chromosomal regions, neg1 and neg2, were found to be essential. Deletion of neg1, involved in nitrite provision for N-N bond formation, reduced production to [~]10%, while deletion of neg2, which directs {beta}-lysine generation and scaffold assembly, abolished it completely. Isotope-labeling experiments confirmed nitrite incorporation. Transcriptomic and proteomic analyses further supported the involvement of both regions. The heterologous expression of neg1 along with the neg2 region in Streptomyces albidoflavus reconstituted negamycin biosynthesis, confirming the unusual involvement of two distant gene clusters in the biosynthesis, and provides a foundation for biotechnological production and further development of this promising antibiotic. SIGNIFICANCEThe rapid rise of antimicrobial resistance (AMR), particularly among Gram-negative ESKAPE pathogens, represents one of the most urgent global health threats. Despite this, the discovery and development of new antibiotics have stagnated. Addressing this challenge requires the exploration of natural products with novel mechanisms of action, alongside the development of scalable production strategies. Negamycin has emerged as a compelling candidate in this regard, characterized by an unusual mechanism of action and therapeutic potential extending beyond traditional antibacterial use. However, its development has been constrained by low production yields in the native producer. In this study, we identify and characterize the biosynthetic genes responsible for negamycin production, providing a foundation for pathway engineering, yield optimization, and the rational design of new analogs.

microbiology↗

bioRxiv2020

Shotgun lipidomics and mass spectrometry imaging unveil diversity and dynamics in lipid composition in Gammarus fossarum

Sentinel species are playing an indispensable role in monitoring environmental pollution in aquatic ecosystems. Many pollutants found in water prove to be endocrine disrupting chemicals that could cause disruptions in lipid homeostasis in aquatic species. A comprehensive profiling of the lipidome of these species is thus an essential step towards understanding the mechanism of toxicity induced by pollutants. We here extensively examined both the composition and spatial distribution of lipids in freshwater crustacean Gammarus fossarum. The baseline lipidome of gammarids of different gender and reproductive stage was established by high throughput shotgun lipidomics. Spatial lipid mapping by high resolution mass spectrometry imaging led to the discovery of sulfate-based lipids in hepatopancreas and their accumulation in mature oocytes. We uncovered in G. fossarum a diverse and dynamic lipid composition that deepens our understanding of the biochemical changes during development and which could serve as a reference for future ecotoxicological studies.

biochemistry↗

bioRxiv2018

A role for gut microbiota in m6A epitranscriptomic mRNA modifications in different host tissues

The intestinal microbiota modulates host physiology and gene expression via mechanisms that are not fully understood. A recently discovered layer of gene expression regulation is N6-methyladenosine (m6A) modification of mRNA. To unveil if this epitranscriptomic mark in part mediates the impact of the gut microbiota on the host, we analyzed m6A-modifications in transcripts of mice displaying either a conventional, or a modified, or no gut flora. We discovered that the microbiota has a strong influence on m6A-modifications in the cecum, and also, albeit to a lesser extent, in the liver. We furthermore show that a single commensal bacterium, Akkermansia muciniphila, can affect specific m6A modifications. Together, we report here epitranscriptomic modifications as an unexpected level of interaction in the complex interplay between commensal bacteria and their host.

molecular biology↗

bioRxiv2017

Preprint: Environmentally-Friendly Workflow Based on Supercritical Fluid Chromatography and Tandem Mass Spectrometry Molecular Networking For the Discovery of Potent Anti-Viral Leads From Plants

A supercritical fluid chromatography-based targeted purification workflow using tandem mass spectrometry and molecular networking was developed to analyze, annotate and isolate secondary metabolites from complex mixture. This approach was applied for targeted isolation of new antiviral diterpene esters from Euphorbia semiperfoliata whole plant extract. The analysis of bioactive fractions revealed that unknown diterpene esters, including jatrophane esters and phorboids esters, were present in the samples. The purification procedure using semi-preparative-supercritical fluid chromatography led to the isolation and identification of two jatrophane esters (13 and 14) and four 4-deoxyphorbol esters (15-18). Compound 16 was found to display antiviral activity against chikungunya virus (EC50 = 0.45 {micro}M), while compound 15 was found to be a potent and selective inhibitor of HIV-1 replication in a recombinant virus assay (EC50 = 13 nM). This study showed that supercritical fluid chromatography-based workflow and molecular networking can facilitate and accelerate the discovery of bioactive small molecules by targeted molecules of interest, while minimizing the use of toxic solvents.\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=104 SRC=\"FIGDIR/small/106153_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (23K):\norg.highwire.dtl.DTLVardef@191802aorg.highwire.dtl.DTLVardef@1755ab8org.highwire.dtl.DTLVardef@196edf5org.highwire.dtl.DTLVardef@1e0a1e0_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗