Biology subjects

Jacquier, N.

Publications and source records attributed to Jacquier, N..

6 recordsLinked to original sources

bioRxiv2026

In planta haploid induction in maize and tomato through disruption of KOKOPELLI

Haploid induction is a key component of doubled haploid technology and an increasingly valuable tool for plant breeding, genome editing, and clonal seed production. While in planta haploid induction through haploid inducer lines offers significant advantages over in vitro approaches, its application remains limited in many crop species. Previously, disruption of the sperm cell-expressed KOKOPELLI (KPL) gene was shown to induce maternal haploids in Arabidopsis thaliana. Here, we report the creation of novel haploid inducer lines in two globally important crops, maize (Zea mays), a major staple food crop, and tomato (Solanum lycopersicum), a widely cultivated vegetable crop. Using targeted genome editing, we generated mutations in KPL orthologs and demonstrated that loss of KPL function confers haploid induction capacity, enabling the production of haploid seedlings in both species. These findings establish KPL as a conserved target to trigger haploid induction and expand the genetic toolbox available for haploid inducer development in crop species.

Plant Biology↗

bioRxiv2025

In vitro resistance selection in Acinetobacter baumannii against the antimicrobial peptide TAT-RasGAP317-326 can cause cross-resistance to polymyxins through mutations in pmrAB

Antibiotic resistance is a growing public health concern. In this context, there is an urgent need of alternative antimicrobial agents effective towards multidrug-resistant bacteria. Antimicrobial peptides (AMPs) are naturally occurring peptides, part of the first antimicrobial line of defence of a wide variety of organisms. AMPs were identified as a promising alternative to classical antibiotics with a low potential of resistance emergence towards them. However, increasing pieces of evidence indicate that resistance to AMPs may be more common than expected. TAT-RasGAP317-326 is a semi-synthetic peptide first developed as an anticancer agent and later identified as an antibacterial agent. This peptide has a potent activity against Gram-negative bacteria, with a particularly low MIC (8 {micro}g/ml) against Acinetobacter baumannii. While attempting to decipher the mode of action of TAT-RasGAP317-326, we performed in vitro resistance selection on Escherichia coli and only detected specific resistance to TAT-RasGAP317-326, without emergence of cross-resistance to other antimicrobial agents. In this study, we performed a similar in vitro resistance selection assay using several A. baumannii strains. We repeatedly observed, upon selection with TAT-RasGAP317-326, the emergence of cross-resistance to polymyxins, a family of polypeptidic antibiotics used as last resort agents towards multiresistant bacteria. A majority of the cross-resistant strains we selected had mutations in the pmrAB operon. Importantly, some of these mutations were identical to mutations detected in polymyxins resistant clinical isolates. Such mutations are known to cause resistance to polymyxins through modifications of the charge and structure of lipopolysaccharides at the bacterial surface. We thus show here that contact of A. baumannii with a semi-synthetic peptide structurally very different from polymyxins can induce the emergence of cross-resistance towards them. This indicates that caution should be taken with the clinical use of AMPs, since unexpected cross-resistance could emerge. Author SummaryAntimicrobial peptides are currently deployed as an alternative treatment option towards multidrug resistant bacteria. However, little is known on the capacity of bacterial pathogens to develop resistance to these peptides. Here we show that the nosocomial pathogen Acinetobacter baumannii can develop resistance to the antimicrobial peptide TAT-RasGAP317-326 in vitro. In half of the cases, this was accompanied by cross-resistance to polymyxins, polypeptidic antibiotics used as last-resort treatment for multidrug resistant bacteria. We showed that this cross-resistance was generally caused by acquisition of mutations in the pmrAB genes, as observed in polymyxin-resistant clinical isolates. These mutations apparently cause changes in lipopolysaccharide structure, affecting the affinity of both TAT-RasGAP317-326 and polymyxins to the bacterial surface. Our results indicate that antimicrobial peptides should be used carefully, since they might induce cross-resistance to other antimicrobial agents. We observed this cross-resistance emergence with one peptide, TAT-RasGAP317-326 towards one pathogenic bacterium, A. baumannii. In the future, we need to determine whether such phenomena can happen with other bacterial species and other antimicrobial peptides.

microbiology↗

bioRxiv2022

An NlpC/P60 protein catalyzes a key step in peptidoglycan recycling at the intersection of energy recovery, cell division and immune evasion in the intracellular pathogen Chlamydia trachomatis

The obligate intracellular Chlamydiaceae do not need to resist osmotic challenges and thus lost their cell wall in the course of evolution. Nevertheless, these pathogens maintain a rudimentary peptidoglycan machinery for cell division. They build a transient peptidoglycan ring, which is remodeled during the process of cell division and degraded afterwards. Uncontrolled degradation of peptidoglycan poses risks to the chlamydial cell, as essential building blocks might get lost or trigger host immune response upon release into the host cell. Here, we provide evidence that a primordial enzyme class prevents energy intensive de novo synthesis and uncontrolled release of immunogenic peptidoglycan subunits in Chlamydia trachomatis. Our data indicate that the homolog of a Bacillus NlpC/P60 protein is widely conserved among Chlamydiales. We show that the enzyme is tailored to hydrolyze peptidoglycan-derived peptides, does not interfere with peptidoglycan precursor biosynthesis, and is targeted by cysteine protease inhibitors in vitro and in cell culture. The peptidase plays a key role in the underexplored process of chlamydial peptidoglycan recycling. Our study suggests that chlamydiae orchestrate a closed-loop system of peptidoglycan ring biosynthesis, remodeling, and recycling to support cell division and maintain long-term residence inside the host. Operating at the intersection of energy recovery, cell division and immune evasion, the peptidoglycan recycling NlpC/P60 peptidase could be a promising target for the development of drugs that combine features of classical antibiotics and anti-virulence drugs. Author SummaryFree-living bacteria are wrapped by a peptidoglycan cell wall. This envelope provides shape and protects from osmotic stress, while also triggering human immune defense. Chlamydial pathogens live inside human cells and dispensed with a cell wall in their isotonic niche. Instead, they produce a transient peptidoglycan ring that is essentially involved in cell division. Recycling of peptidoglycan is likely important for chlamydiae to maintain a complete cycle of peptidoglycan ring synthesis and cell division. Moreover, the process may help to save energy and to protect from recognition through the immune system. Despite a potentially central role in cell viability and pathogenicity almost nothing is known about recycling of peptidoglycan in chlamydiae. The minimalist organisms lack all enzymes known to catalyze the process in model organism Escherichia coli. Here, we found an NlpC/P60 enzyme to serve a critical step in decomposing peptidoglycan ring derived peptides in Chlamydia trachomatis. Our data indicate that the peptidase recycles energy cost intensive components and breaks down the minimal recognition motif of innate immune factor NOD1. We also identified a natural lead compound to inhibit the NlpC/P60 enzyme opening the way for innovative anti-chlamydial drug development at the intersection of energy recovery, cell division, and immune evasion.

microbiology↗

bioRxiv2022

In vitro synergistic action of TAT-RasGAP317-326 peptide with antibiotics against Gram-negative pathogens

ObjectivesMultidrug-resistant (MDR) bacteria are a continuously increasing threat for medicine, causing infections recalcitrant to antibiotics. Antimicrobial peptides (AMPs) were identified as alternatives to antibiotics, being naturally occurring short peptides and part of the innate immune system of a vast majority of organisms. However, the clinical application of AMPs is limited by suboptimal pharmacokinetic properties and relatively high toxicity. Combinatorial treatments using AMPs and classical antibiotics may decrease the concentrations of AMPs required for bacterial eradication, thus lowering the side effects of these peptides. MethodsHere, we investigate the in vitro efficiency of combinations of the recently described antimicrobial peptide TAT-RasGAP317-326 with a panel of commonly used antimicrobial agents against three Gram-negative bacteria: Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii using checkerboard and time-kill assays. ResultsWe identified synergistic combinations towards all three bacteria and demonstrated that these combinations had an increased bactericidal effect compared to individual drugs. Moreover, combinations were also effective against clinical isolates of A. baumannii. Finally, combination of TAT-RasGAP317-326 and meropenem had a promising antibiofilm effect towards A. baumannii. ConclusionTaken together, our results indicate that combinations of TAT-RasGAP317-326 with commonly-used antimicrobial agents may lead to the development of new treatment protocols against infections caused by MDR bacteria.

microbiology↗

bioRxiv2020

Characterization of the antimicrobial activity of the cell-penetrating peptide TAT-RasGAP317-326

Antibiotic resistance is an increasing threat for public health, underscoring the need for new antibacterial agents. Antimicrobial peptides (AMPs) represent an alternative to classical antibiotics. TAT-RasGAP317-326 is a recently described AMP effective against a broad range of bacteria, but little is known about the conditions that may influence its activity. Using RNA-sequencing and screening of mutant libraries, we show that Escherichia coli and Pseudomonas aeruginosa respond to TAT-RasGAP317-326 by regulating metabolic and stress response pathways, possibly implicating two-component systems. Our results also indicate that bacterial surface properties, in particular integrity of the lipopolysaccharide layer, influence peptide binding and entry. Finally, we found differences between bacterial species with respect to their rate of resistance emergence against this peptide. Our findings provide the basis for future investigation on the mode of action of this peptide and its potential clinical use as an antibacterial agent.

microbiology↗

bioRxiv2020

The antimicrobial peptide TAT-RasGAP317-326 inhibits the formation and the expansion of bacterial biofilms in vitro

Biofilms are structured aggregates of bacteria embedded in a self-produced matrix. Pathogenic bacteria can form biofilms on surfaces and in tissues leading to nosocomial and chronic infections. While antibiotics are largely inefficient in limiting biofilm formation and expansion, antimicrobial peptides (AMPs) are emerging as alternative anti-biofilm treatments. In this study, we explore the effect of the newly described AMP TAT-RasGAP317-326 on Acinetobacter baumannii, Pseudomonas aeruginosa and Staphylococcus aureus biofilms. We observe that TAT-RasGAP317-326 inhibits the formation of biofilms at concentrations equivalent or two times superior to the minimal inhibitory concentration (MIC) of the corresponding planktonic bacteria. Moreover, TAT-RasGAP317-326 limits the expansion of A. baumannii and P. aeruginosa established biofilms at concentrations 2-4 times superior to the MIC. These results further confirm the potential of AMPs against biofilms, expand the antimicrobial potential of TAT-RasGAP317-326 and support further development of this peptide as an alternative antimicrobial treatment.

microbiology↗