Fabrice Dupuy

The trade-off between reducing pesticide use and ensuring effective crop protection is a key challenge for sustainable agriculture. Stimulating the plant’s natural defense mechanisms represents a promising alternative. In this study, we evaluated the potential of pulsed light as a physical elicitor in tomato (Solanum lycopersicum). This technology is based on the emission of brief but intense light flashes, covering a broad spectrum (from UV-C to infrared), capable of simultaneous activation of multiple signaling pathways. Tomato plants were treated using a standard protocol and subjected to biochemical, transcriptional, physiological, and pathological analyses. The treatment significantly increased the activity of defense-related and antioxidant enzymes, the accumulation of phenolic compounds and callose, and the expression of key immunity-related genes. Upon Botrytis cinerea inoculation, pretreated tomato plants showed enhanced defense responses and a significant reduction in disease severity, indicating a priming effect. The standard protocol did not impair photosynthesis, growth, or yield. These findings highlight pulsed light as an innovative technology for integrated crop protection.

Stimulation of plant defenses by elicitors is an alternative strategy to reduce pesticide use. In this study, we examined the elicitor properties of a by-product of the industrial extraction of agar from the red alga Gelidium sesquipedale. Agar extraction process leads to the formation of an alkaline residue which is poorly valorized. This by-product has been analyzed for its chemical composition. It contains 44% minerals and, among the organic compounds, sugars are the most represented and encompass 12.5% of the dry matter. When sprayed on tomato plants, this by-product enhanced the levels of defense markers such as peroxidase or phenylalanine ammonia lyase activities. Furthermore, this treatment increased the expression levels of the pathogenesis-related gene, PR9 encoding peroxidase. A field trial conducted on grapevine revealed that spraying treatment with this by-product resulted in a reduction of the macroscopic disease symptoms induced by Plasmospora viticola, with 40 to 60% efficacy. These results indicate that this agar extraction by-product could be used as a plant defense stimulator.

The submicrometric fraction of surface sediments that accumulate in the bottom of dam reservoirs represent important sources of nutrients and contaminants in freshwater systems. However, assessing their stability in the presence of sediment bacteria as well as their bioavailability in the sediment remains poorly understood. We hypothesized that sediment’s bacteria are able to extract nutrients from sedimentary colloids (Pseudomonas sp. and Gram-positive Mycolicibacterium sp.). The results demonstrated that bacteria were able to maintain their metabolic activity (the acidification of the growth medium and the production of organic ligands) in the presence of colloids as the sole source of iron (Fe) and regardless of their chemical composition. This demonstrates that bioavailable Fe, aside from ionic forms, can also occur in colloidal forms. However, the bacteria also catalyzed the release of potentially toxic metallic elements (such as Pb) associated with colloids. These results help improve our understanding of the processes that influence contaminants’ mobility in the ecosystems as well as provide an important insight into current research evaluating the bioavailability of different forms of nutrients.

Myogenesis is initiated by myoblast differentiation and fusion to form myotubes and muscle fibres. A population of myoblasts, known as satellite cells, is responsible for post-natal growth of muscle and for its regeneration. This differentiation requires many changes in cell behaviour and its surrounding environment. These modifications are tightly regulated over time and can be characterized through the study of changes in gene expression associated with this process. During the initial myogenesis steps, using the myoblast cell line C2C12 as a model, Janot et al. (2009) showed significant variations in expression for genes involved in pathways of glycolipid synthesis. In this study we used murine satellite cells (MSC) and their ability to differentiate into myotubes or early fat storage cells to select glycosylation related genes whose variation of expression is myogenesis specific.

Background: Several global transcriptomic and proteomic approaches have been applied in order to obtain new molecular insights on skeletal myogenesis, but none has generated any specific data on glycogenome expression, and thus on the role of glycan structures in this process, despite the involvement of glycoconjugates in various biological events including differentiation and development. In the present study, a quantitative real-time RT-PCR technology was used to profile the dynamic expression of 375 glycogenes during the differentiation of C2C12 myoblasts into myotubes. Results: Of the 276 genes expressed, 95 exhibited altered mRNA expression when C2C12 cells differentiated and 37 displayed more than 4-fold up- or down-regulations. Principal Component Analysis and Hierarchical Component Analysis of the expression dynamics identified three groups of coordinately and sequentially regulated genes. The first group included 12 down-regulated genes, the second group four genes with an expression peak at 24 h of differentiation, and the last 21 up-regulated genes. These genes mainly encode cell adhesion molecules and key enzymes involved in the biosynthesis of glycosaminoglycans and glycolipids (neolactoseries, lactoseries and ganglioseries), providing a clearer indication of how the plasma membrane and extracellular matrix may be modified prior to cell fusion. In particular, an increase in the quantity of ganglioside G_M3 at the cell surface of myoblasts is suggestive of its potential role during the initial steps of myogenic differentiation. Conclusion: For the first time, these results provide a broad description of the expression dynamics of glycogenes during C2C12 differentiation. Among the 37 highly deregulated glycogenes, 29 had never been associated with myogenesis. Their biological functions suggest new roles for glycans in skeletal myogenesis.

All vertebrate α3- and α3/4-FUTs possess the characteristic acceptor-binding motif VxxHH(W/R)(D/E). FUT6 and FUTb enzymes, harboring R in the acceptor-binding motif, transfer fucose in α1,3 linkage, whereas FUT3 and FUT5 enzymes with W at the candidate position can also transfer fucose in α1,4 linkage—FUT3 being more efficient than FUT5. To determine the involvement of the W/R residue in acceptor recognition, we produced 34 variants of human FUT3, FUT5, FUT6, and ox FUTb Lewis enzymes. Among the FUT3 variants where W¹¹¹ was replaced by the other amino acids, only enzymes with an aromatic residue at the candidate position kept about 50% of α1,4 activity and showed no changes in K_m values for GDP-Fuc donor and H-type 1 acceptor substrates. All other substitutions produced enzymes with less than 20% of the α1,4 activity. Thus the ability of α3/4-FUTs to recognize type 1 substrates involves the aromatic character of W in the acceptor-binding domain. The α1,3 activity of FUT6 and FUTb significantly decreased when their R residue was substituted by basic or charged residues. Moreover, FUT3 and FUT5 variants with W→R substitution had a better affinity for H-type 2 substrate and higher α1,3 activities. Therefore the optimal fucose addition in α1,3 linkage requires the R residue in the acceptor-binding motif of Lewis FUTs.