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MreB forms subdiffraction nanofilaments during active growth in Bacillus subtilis
No full textThe actin-like MreB protein is a key player of the machinery controlling the elongation and maintenance of the cell shape of most rod-shaped bacteria. This protein is known to be highly dynamic, moving along the short axis of cells, presumably reflecting the movement of cell wall synthetic machineries during the enzymatic assembly of the peptidoglycan mesh. The ability of MreB proteins to form polymers is not debated, but their structure, length, and conditions of establishment have remained unclear and the subject of conflicting reports. Here we analyze various strains of Bacillus subtilis, the model for Gram-positive bacteria, and we show that MreB forms subdiffraction-limited, less than 200 nm-long nanofilaments on average during active growth, while micron-long filaments are a consequence of artificial overaccumulation of the protein. Our results also show the absence of impact of the size of the filaments on their speed, orientation, and other dynamic properties conferring a large tolerance to B. subtilis toward the levels and consequently the lengths of MreB polymers. Our data indicate that the density of mobile filaments remains constant in various strains regardless of their MreB levels, suggesting that another factor determines this constant.IMPORTANCE The construction of the bacterial cell envelope is a fundamental topic, as it confers its integrity to bacteria and is consequently the target of numerous antibiotics. MreB is an essential protein suspected to regulate the cell wall synthetic machineries. Despite two decades of study, its localization remains the subject of controversies, its description ranging from helical filaments spanning the entire cell to small discrete entities. The true structure of these filaments is important because it impacts the model describing how the machineries building the cell wall are associated, how they are coordinated at the scale of the entire cell, and how MreB mediates this regulation. Our results shed light on this debate, revealing the size of native filaments in B. subtilis during growth. They argue against models where MreB filament size directly affects the speed of synthesis of the cell wall and where MreB would coordinate distant machineries along the side wall
Altered spinogenesis in iPSC-derived cortical neurons from patients with autism carrying de novo SHANK3 mutations
No full textThe synaptic protein SHANK3 encodes a multidomain scafold protein expressed at the postsynaptic
density of neuronal excitatory synapses. We previously identifed de novo SHANK3 mutations in
patients with autism spectrum disorders (ASD) and showed that SHANK3 represents one of the major
genes for ASD. Here, we analyzed the pyramidal cortical neurons derived from induced pluripotent stem
cells from four patients with ASD carrying SHANK3 de novo truncating mutations. At 40–45 days after
the diferentiation of neural stem cells, dendritic spines from pyramidal neurons presented variable
morphologies: flopodia, thin, stubby and muschroom, as measured in 3D using GFP labeling and
immunofuorescence. As compared to three controls, we observed a signifcant decrease in SHANK3
mRNA levels (less than 50% of controls) in correlation with a signifcant reduction in dendritic spine
densities and whole spine and spine head volumes. These results, obtained through the analysis of de
novo SHANK3 mutations in the patients’ genomic background, provide further support for the presence
of synaptic abnormalities in a subset of patients with ASD
The genetic structure of the European black pine (Pinus nigra Arnold) is shaped by its recent Holocene demographic history.
No full textFragmentation acting over geological times confers wide, biogeographical scale, genetic diversity patterns to species, through demographic and natural selection processes. To test the effects of historical fragmentation on the genetic diversity and differentiation of a major European forest tree and to resolve its demographic history, we describe and model its spatial genetic structure and gene 30 genealogy. We then test which Pleistocene event, whether recent or ancient, could explain its widespread but patchy geographic distribution using population genetic data, environmental data and realistic demographic timed scenarios. The taxon of interest is a conifer forest tree, Pinus nigra (Arnold), the European black pine, whose populations are located in the mountains of southern Europe and North Africa, most frequently at mid35 elevation. We used a set of different genetic markers, both neutral and potentially adaptive, and either bi-parentally or paternally inherited, and we sampled natural populations across the entire range of the species. We analysed the data using frequentist population genetic methods as well as Bayesian inference methods to calibrate realistic, demographic timed scenarios. Species with geographically fragmented distribution areas are expected to display strong among40 population genetic differentiation and low within-population genetic diversity. Contrary to these expectations, we show that the current diversity of Pinus nigra and its weak genetic spatial structure are best explained as resulting from late Pleistocene or early Holocene fragmentation of one ancestral population into seven genetic lineages, which we found to be the main biogeographical contributors of the natural black pine forests of today. Gene flow among the different lineages is strong across forests 45 and many current populations are admixed between lineages. We propose to modify the currently accepted international nomenclature made of five subspecies and name these seven lineages using regionally accepted subspecies-level names
Understanding the phyllosphere microbiome assemblage in grape species (Vitaceae) with amplicon sequence data structures
No full textImpacts of plant genotype on microbial assemblage in the phyllosphere (above-ground parts of plants, which predominantly consists of the set of photosynthetic leaves) of Vitis vinifera cultivars have been studied previously but the impact of grape species (under the grape family Vitaceae) was never investigated. Considering the fact, that the phyllosphere microbiome may have profound effects on host plant health and its performance traits, studying the impact of grape species in microbial taxa structuring in the phyllosphere could be of crucial importance. We performed 165 and ITS profiling (for bacteria and fungi respectively) to access genus level characterization of the microflora present in the leaf phyllosphere of five species within this plant family, sampled in two successive years from the repository situated in the Mediterranean. We also performed alpha and beta-diversity analyses with robust statistical estimates to test the impacts of grape species and growing year, over a two-year period. Our results indicated the presence of complex microbial diversity and assemblages in the phyllosphere with a significant effect of both factors (grape species and growing year), the latter effect is being more pronounced. We also compared separate normalization methods for high-throughput microbiome data-sets followed by differential taxa abundance analyses. The results suggested the predominance of a particular normalization method over others. This also indicated the need for more robust normalization methods to study the differential taxa abundance among groups in microbiome research
Evaluating the “Soil stabilisation and control of erosion” ecosystem service provided by agricultural ecosystems over the French territory
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Rethinking False Spring Risk
No full textTemperate plants are at risk of being exposed to late spring freezes. These freeze events—often called false springs—are one of the strongest factors determining temperate plants species range limits and can impose high ecological and economic damage. As climate change may alter the prevalence and severity of false springs, our ability to forecast such events has become more critical, and it has led to a growing body of research. Many false spring studies largely simplify the myriad complexities involved in assessing false spring risks and damage. While these studies have helped advance the field and may provide useful estimates at large scales, studies at the individual to community levels must integrate more complexity for accurate predictions of plant damage from late spring freezes. Here we review current metrics of false spring, and how, when and where plants are most at risk of freeze damage. We highlight how life stage, functional group, species differences in morphology and phenology, and regional climatic differences contribute to the damage potential of false springs. More studies aimed at understanding relationships among species tolerance and avoidance strategies, climatic regimes, and the environmental cues that underlie spring phenology would improve predictions at all biological levels. An integrated approach to assessing past and future spring freeze damage would provide novel insights into fundamental plant biology, and offer more robust predictions as climate change progresses, which is essential for mitigating the adverse ecological and economic effects of false springs
Aminoacids and flavonoids profiling in tempranillo berries can be modulated by the arbuscular mycorrhizal fungi
No full textBackground: Vitis vinifera L. cv. Tempranillo is cultivated over the world for its wine of high quality. The association of Tempranillo with arbuscular mycorrhizal fungi (AMF) induced the accumulation of phenolics and carotenoids in leaves, affected the metabolism of abscisic acid (ABA) during berry ripening, and modulated some characteristics and quality aspects of grapes. The objective of this study was to elucidate if AMF influenced the profiles and the content of primary and secondary metabolites determinants for berry quality in Tempranillo. (2) Methods: Fruit-bearing cuttings inoculated with AMF or uninoculated were cultivated under controlled conditions. (3) Results: Mycorrhizal symbiosis modified the profile of metabolites in Tempranillo berries, especially those of the primary compounds. The levels of glucose and amino acids clearly increased in berries of mycorrhized Tempranillo grapevines, including those of the aromatic precursor amino acids. However, mycorrhizal inoculation barely influenced the total amount and the profiles of anthocyanins and flavonols in berries. (4) Conclusions: Mycorrhizal inoculation of Tempranillo grapevines may be an alternative to the exogenous application of nitrogen compounds in order to enhance the contents of amino acids in grapes, which may affect the aromatic characteristics of wines
Recognition of elicitors in grapevine: From mamp and damp perception to induced resistance
No full textIn a context of a sustainable viticulture, the implementation of innovative eco-friendly strategies, such as elicitor-triggered immunity, requires a deep knowledge of the molecular mechanisms underlying grapevine defense activation, from pathogen perception to resistance induction. During plant-pathogen interaction, the first step of plant defense activation is ensured by the recognition of microbe-associated molecular patterns, which are elicitors directly derived from pathogenic or beneficial microbes. Vitis vinifera, like other plants, can perceive elicitors of different nature, including proteins, amphiphilic glycolipid, and lipopeptide molecules as well as polysaccharides, thanks to their cognate pattern recognition receptors, the discovery of which recently began in this plant species. Furthermore, damage-associated molecular patterns are another class of elicitors perceived by V. vinifera as an invader's hallmark. They are mainly polysaccharides derived from the plant cell wall and are generally released through the activity of cell wall-degrading enzymes secreted by microbes. Elicitor perception and subsequent activation of grapevine immunity end in some cases in efficient grapevine resistance against pathogens. Using complementary approaches, several molecular markers have been identified as hallmarks of this induced resistance stage. This review thus focuses on the recognition of elicitors by Vitis vinifera describing the molecular mechanisms triggered from the elicitor perception to the activation of immune responses. Finally, we discuss the fact that the link between elicitation and induced resistance is not so obvious and that the formulation of resistance inducers remains a key step before their application in vineyards
Des bandes fleuries pour les auxiliaires dans les grandes cultures ? Oui mais lesquelles ?
No full textDans la continuité des projets Auximore et Muscari, le projet BiodiversiD a permis de réaliser des essais
visant à comparer l’attractivité pour des insectes auxiliaires (chrysopes, syrphes, coccinelles, punaises
prédatrices, hyménoptères parasitoïdes…) de différents types de mélanges fleuris. Des observations
sur fleurs, des collectes et des analyses du contenu des tubes digestifs avec identification du pollen ont
été réalisées pour connaître les plantes les plus attractives utilisées dans les bandes fleuries. Nous
avons également évalué l’impact de ces bandes fleuries sur la quantité et la qualité des auxiliaires dans
les parcelles de blé, jusqu’à 100 m de la bordure.Through BiodiversiD project, following Auximore Casdar and in parallel with Muscari Casdar, tests were
carried out to compare different types of flowering mixtures on the attractiveness of auxiliary insects
(green lacewings, hoverflies, ladybugs, predatory bugs, parasitoid hymenoptera…). Observations on
flowers, collections, analyses of the content of digestive tracts, and identification of pollen grains were
made to identify the most attractive plants within the flower strips. We also assessed the impact of these
flowering strips on the quantity and quality of auxiliaries in wheat crops, up to 100 m from the curb