Biology subjects

Teulon, J.-M.

Publications and source records attributed to Teulon, J.-M..

3 recordsLinked to original sources

bioRxiv2023

Correlation between plant cell wall stiffening and root extension arrest phenotype in the combined abiotic stress of Fe and Al

The plasticity and growth of plant cell walls (CWs) remain poorly understood at the molecular level. In this work, we used atomic force microscopy (AFM) to observe elastic responses of the root transition zone of 4-day-old Arabidopsis thaliana wild type and almt1 mutant seedlings grown under Fe or Al stresses. The elastic parameters were deduced from force-distance measurements by AFM using the trimechanic-3PCS framework. In all metal stresses tested, the presence of single metal species Fe2+ or Al3+ at 10 {micro}M exerts no noticeable effect on the root growth compared with the control conditions. On the contrary, a mix of both the metal ions produced a strong root extension arrest concomitant with significant increase of CW stiffness. This was not found for the almt1 mutant which substantially abolishes the ability to exude malate. By raising the concentration of either Fe2+ or Al3+ to 20 {micro}M, no root extension arrest was observed; nevertheless, a rise of root stiffness occurred. Our results indicate that the combination of Fe2+ and Al3+ with exuded malate is crucial for both CW stiffening and root extension arrest. However, stiffness increase induced by single Fe or Al metal is not sufficient for arresting root growth. Summary statementWe record the change in stiffness of the external primary cell wall of living Arabidopsis thaliana seedlings in presence of metallic stress using atomic force microscopy. Results reveals for the first time the uncoupling between mechanical response (CW stiffening) and root extension arrest.

plant biology↗

bioRxiv2021

De novo determination of mosquitocidal Cry11Aa and Cry11Ba structures from naturally-occurring nanocrystals

Cry11Aa and Cry11Ba are the two most potent toxins produced by mosquitocidal Bacillus thuringiensis subsp. israelensis and jegathesan, respectively. The toxins naturally crystallize within the host; however, the crystals are too small for structure determination at synchrotron sources. Therefore, we applied serial femtosecond crystallography at X-ray free electron lasers to in vivo-grown nanocrystals of these toxins. The structure of Cry11Aa was determined de novo using the single-wavelength anomalous dispersion method, which in turn enabled the determination of the Cry11Ba structure by molecular replacement. The two structures reveal a new pattern for in vivo crystallization of Cry toxins, whereby each of their three domains packs with a symmetrically identical domain, and a cleavable crystal packing motif is located within the protoxin rather than at the termini. The diversity of in vivo crystallization patterns suggests explanations for their varied levels of toxicity and rational approaches to improve these toxins for mosquito control.

molecular biology↗

bioRxiv2021

Structural and functional characterization of DdrC, a novel DNA damage-induced nucleoid associated protein involved in DNA compaction

Deinococcus radiodurans is a spherical bacterium well-known for its outstanding resistance to DNA-damaging agents. Exposure to such agents leads to drastic changes in the transcriptome of D. radiodurans. In particular, four Deinococcus-specific genes, known as DNA Damage Response genes, are strongly up-regulated and have been shown to contribute to the resistance phenotype of D. radiodurans. One of these, DdrC, is expressed shortly after exposure to {gamma}-radiation and is rapidly recruited to the nucleoid. In vitro, DdrC has been shown to compact circular DNA, circularize linear DNA, anneal complementary DNA strands and protect DNA from nucleases. To shed light on the possible functions of DdrC in D. radiodurans, we determined the crystal structure of the domain-swapped DdrC dimer at a resolution of 2.2 [A] and further characterized its DNA binding and compaction properties. Notably, we show that DdrC bears two asymmetric DNA binding sites located on either side of the dimer and can modulate the topology and level of compaction of circular DNA. These findings suggest that DdrC may be a DNA damage-induced nucleoid-associated protein that enhances nucleoid compaction to limit the dispersion of the fragmented genome and facilitate DNA repair after exposure to severe DNA damaging conditions.

microbiology↗