The synthesis of the rhamnogalacturonan II component 3-deoxy-D-manno-2-octulosonic acid (Kdo) is required for pollen tube growth and elongation

Despite a very complex structure, the sugar composition of the rhamnogalacturonan II (RG-II) pectic fraction is extremely conserved. Among its constituting monosaccharides is the seldom-observed eight-carbon sugar 3-deoxy-D-manno-octulosonic acid (Kdo), whose phosphorylated precursor is synthesized by Kdo-8-P synthase. As an attempt to alter specifically the RG-II structure in its sugar composition and assess the consequences on the function of RG-II in cell wall and its relationship with growth, Arabidopsis null mutants were sought in the genes encoding Kdo-8-P synthase. Here, the isolation and characterization of one null mutant for the isoform 1 (AtkdsA1-S) and two distinct null mutants for the isoform 2 of Arabidopsis Kdo-8-P synthase (AtkdsA2-V and AtkdsA2-S) are described. Evidence is provided that AtkdsA2 gene expression is preferentially associated with plantlet organs displaying a meristematic activity, and that it accounts for 75% of the mRNAs to be translated into Kdo-8-P synthase. Furthermore, this predominant expression of AtKDSA2 over AtKDSA1 was confirmed by quantification of the cytosolic Kdo content in the mutants, in a variety of ecotypes. The inability to identify a double knockout mutant originated from pollen abortions, due to the inability of haploid pollen of the AtkdsA1- AtkdsA2- genotype to form an elongated pollen tube properly and perform fertilization

The human OPA1delTTAG mutation induces premature age-related systemic neurodegeneration in mouse

Dominant optic atrophy is a rare inherited optic nerve degeneration caused by mutations in the mitochondrial fusion gene OPA1. Recently, the clinical spectrum of dominant optic atrophy has been extended to frequent syndromic forms, exhibiting various degrees of neurological and muscle impairments frequently found in mitochondrial diseases. Although characterized by a specific loss of retinal ganglion cells, the pathophysiology of dominant optic atrophy is still poorly understood. We generated an Opa1 mouse model carrying the recurrent Opa1(delTTAG) mutation, which is found in 30% of all patients with dominant optic atrophy. We show that this mouse displays a multi-systemic poly-degenerative phenotype, with a presentation associating signs of visual failure, deafness, encephalomyopathy, peripheral neuropathy, ataxia and cardiomyopathy. Moreover, we found premature age-related axonal and myelin degenerations, increased autophagy and mitophagy and mitochondrial supercomplex instability preceding degeneration and cell death. Thus, these results support the concept that Opa1 protects against neuronal degeneration and opens new perspectives for the exploration and the treatment of mitochondrial diseases

Differential Expression of Salivary Proteins between Susceptible and Insecticide-Resistant Mosquitoes of Culex quinquefasciatus

Background: The Culex quinquefasciatus mosquito, a major pest and vector of filariasis and arboviruses in the tropics, has developed multiple resistance mechanisms to the main insecticide classes currently available in public health. Among them, the insensitive acetylcholinesterase (ace-1(R) allele) is widespread worldwide and confers cross-resistance to organophosphates and carbamates. Fortunately, in an insecticide-free environment, this mutation is associated with a severe genetic cost that can affect various life history traits. Salivary proteins are directly involved in human-vector contact during biting and therefore play a key role in pathogen transmission. Methods and Results: An original proteomic approach combining 2D-electrophoresis and mass spectrometry was adopted to compare the salivary expression profiles of two strains of C. quinquefasciatus with the same genetic background but carrying either the ace-1(R) resistance allele or not (wild type). Four salivary proteins were differentially expressed (> 2 fold, P < 0.05) in susceptible (SLAB) and resistant (SR) mosquito strains. Protein identification indicated that the D7 long form, a major salivary protein involved in blood feeding success, presented lower expression in the resistant strain than the susceptible strain. In contrast, three other proteins, including metabolic enzymes (endoplasmin, triosephosphate isomerase) were significantly over-expressed in the salivary gland of ace-1(R) resistant mosquitoes. A catalogue of 67 salivary proteins of C. quinquefasciatus sialotranscriptome was also identified and described. Conclusion: The "resistance"-dependent expression of salivary proteins in mosquitoes may have considerable impact on biting behaviour and hence on the capacity to transmit parasites/viruses to humans. The behaviour of susceptible and insecticide-resistant mosquitoes in the presence of vertebrate hosts and its impact on pathogen transmission urgently requires further investigation

A Set of 100 Chloroplast DNA Primer Pairs to Study Population Genetics and Phylogeny in Monocotyledons

Chloroplast DNA sequences are of great interest for population genetics and phylogenetic studies. However, only a small set of markers are commonly used. Most of them have been designed for amplification in a large range of Angiosperms and are located in the Large Single Copy (LSC). Here we developed a new set of 100 primer pairs optimized for amplification in Monocotyledons. Primer pairs amplify coding (exon) and non-coding regions (intron and intergenic spacer). They span the different chloroplast regions: 72 are located in the LSC, 13 in the Small Single Copy (SSC) and 15 in the Inverted Repeat region (IR). Amplification and sequencing were tested in 13 species of Monocotyledons: Dioscorea abyssinica, D. praehensilis, D. rotundata, D. dumetorum, D. bulbifera, Trichopus sempervirens (Dioscoreaceae), Phoenix canariensis, P. dactylifera, Astrocaryum scopatum, A. murumuru, Ceroxylon echinulatum (Arecaceae), Digitaria excilis and Pennisetum glaucum (Poaceae). The diversity found in Dioscorea, Digitaria and Pennisetum mainly corresponded to Single Nucleotide Polymorphism (SNP) while the diversity found in Arecaceae also comprises Variable Number Tandem Repeat (VNTR). We observed that the most variable loci (rps15-ycf1, rpl32-ccsA, ndhF-rpl32, ndhG-ndhI and ccsA) are located in the SSC. Through the analysis of the genetic structure of a wild-cultivated species complex in Dioscorea, we demonstrated that this new set of primers is of great interest for population genetics and we anticipate that it will also be useful for phylogeny and bar-coding studies

Flexoelectric response in soft polyurethane films and their use for large curvature sensing

International audienceThe flexoelectric effect is simply defined as the coupling between the strain gradient and polarization in solid dielectrics. It may be seen as an alternative transduction mechanism to the piezoelectric effect to directly sense the curvature of bent flexible thin structures. In the case of large curvatures, flexible and compliant sensors are required and soft polar elastomers may be suitable for curvature sensing. In this study, we report the flexoelectric characterization of soft semi-crystalline polyurethane (PU) films with thicknesses ranging from 1.7 μm to 350 μm. Dynamic bending experiments have been performed on PU films deposited onto rigid steel substrates in the vicinity of the mechanical resonance frequency of the cantilever beams. Quasi-static flexoelectric coefficients of PU films could be obtained by using a classical oscillating model. A global large increase of μ′12 with the decreasing film thickness was found, especially for thicknesses lower than 25 μm. The variation of μ′12 is explained by the presence of a Young's Modulus gradient through the thickness of PU films. Besides, a concomitant uncommon dramatic decrease in the dielectric constant is observed. The combination of these two effects contributes to enhancing the flexocoupling “F” constant with the decreasing thickness. At last, the potential use of a 6.6 μm-thick soft PU film as a large curvature sensor has been experimentally demonstrated by subjecting a flexible Aluminum foil/Polyethylene terephthalate bilayered cantilever to large deflections. A curvature of about 80 m−1 (radius of curvature of ∼1.2 cm) could be sensed under low frequency (3 Hz) bending motion. These results may pave the way for the development of low cost and easy to implement soft flexoelectric elastomer-based large curvature sensors on highly flexible metallic structures

Visual phenotyping of Wfs1 mutant mice, models of Wolfram syndrome neuronal and diabetic symptoms

Purpose: Wolfram syndrome is an early onset genetic disease (1/160,000) featuring diabetes mellitus and optic neuropathy, associated to mutation in the WFS1 gene. Mouse model with deleted exon 8 of Wolframin shows pancreatic beta cell atrophy, but its visual performance has not been investigated, prompting us to study its visual function and the histopathology of the retina and optic nerve. Methods: Electroretinogram (ERG, retinal function) and visual evoked potentials (VEPs, visual pathway) were performed in Wfs1-/- and Wfs1+/+ mice at 3, 6 and 9 months of age. Fundi were pictured with Micron III apparatus. Retinal ganglion cell (RGC) proportion was determined from Brn3a immuno-labeling of retinal sections. RGC axonal loss was quantified by electron microscopy in transversal optic nerve sections. Results: ERG showed a sex-dependent alteration in Wfs1 mutant mice at 3 months. Photoreceptor response amplitude (a-wave) was increased by 25.5% by Wfs1 mutation in females, while reduced by 28.2% in males. In contrast, positive scotopic threshold responses (pSTR) at the same age were found increased in mutant group by 20.5%. A preliminary study of 7 months male samples showed a severe loss of RGC somas (-50%) and axons in retina and optic nerve respectively. Finally, 7-8 months knocked-in mice presented a severe ocular hypertension. Conclusions: Electrophysiological phenotyping of Wfs1 deleted mouse exon 8 visual function indicate a significant loss of RGC in mutant mouse at 7 month. Structural analysis of retinal ganglion cell somas and axons are conducted to characterize optic neuropathy in these animals

Experimental investigation of the link between static and dynamic wetting by forced wetting of nylon filament

Forced wetting experiments with various liquids were conducted to study the dynamic wetting properties of nylon filament. The molecular-kinetic theory of wetting (MKT) was used to interpret the dynamic contact angle data and evaluate the contact-line friction ζ0 at the microscopic scale. By taking account of the viscosity of the liquid, ζ0 could be related exponentially to the reversible work of adhesion. This clearly establishes an experimental link between the static and dynamic wetting properties of the material. Moreover, statistical analysis of the equilibrium molecular displacement frequency K⁰ and the length of the displacements λ reveals that these two fundamental parameters of the MKT are strongly correlated, not only in the linearized form of the theory (valid close to equilibrium) but also when the nonlinear form of the equations has to be considered at higher wetting speeds.status: publishe

Rapid Structural Phenotyping of Plant Cell Wall Mutants by Enzymatic Oligosaccharide Fingerprinting

ABSTRACT: Various biochemical, chemical, and microspectroscopic methods have been developed throughout the years for the screening and identification of mutants with altered cell wall structure. However, these procedures fail to provide the insight into structural aspects of the cell wall polymers. In this paper, we present various methods for rapidly screening Arabidopsis cell wall mutants. The enzymatic fingerprinting procedures using high-performance anion-exchange-pulsed-amperometric detection liquid chromatography, fluorophore-assisted carbohydrate electrophoresis, and matrix-assisted laser-desorption ionization time of flight (MALDI-TOF) mass spectrometry (MS) were exemplified by the structural analysis of the hemicellulose xyloglucan. All three techniques are able to identify structural alterations of wall xyloglucans in mur1, mur2, and mur3, which in comparison with the wild type have side chain defects in their xyloglucan structure. The quickest analysis was provided by MALDI-TOF MS. Although MALDI-TOF MS per se is not quantitative, it is possible to reproducibly obtain relative abundance information of the various oligosaccharides present in the extract. The lack of absolute quantitation by MALDI-TOF MS was compensated for with a xyloglucan-specific endoglucanase and simple colorimetric assay. In view of the potential for mass screening using MALDI-TOF MS, a PERL-based program was developed to process the spectra obtained from MALDI-TOF MS automatically. Outliers can be identified very rapidly according to a set of defined parameters based on data collected from the wild-type plants. The methods presented here can easily be adopted for the analysis of other wall polysaccharides. MALDI-TOF MS offers a powerful tool to screen and identify cell wall mutants rapidly and efficiently and, more importantly, is able to give initial insights into the structural composition and/or modification that occurs in these mutants

Advances in gene therapy for Wolfram syndrome

The Wolfram Syndrome (WS) is an early onset genetic disease (1/200 000) featuring diabetes mellitus and progressive optic neuropathy ensuing mutations in the WFS1 gene. To date, there is no treatment to stop the progression of the disease. We have characterized the visual impairment of 2 mutants animal models for WFS1 (Wfs1exon8‐/‐ and Wfs1E864K) and shown that these 2 models developed an optic atrophy. We started for 1 year intravitreous micro injections of therapeutic vector AAV2‐CMV‐WFS1 on 1 month‐old Wfs1exon8‐/‐. Our results showed that mice injected exhibited a stabilization of their visual acuity at 3 and 6 months post‐injection, and a decrease of optic disc pallor and optic nerve damage. These promising results demonstrate the validity of the pre‐clinical approach to treat Wolfram Syndrome by gene therapy and encourage further studies under a treatment for the Wolfram Syndrome patients