The Golgi apparatus of eukaryotic cells is known for its central role in the processing, sorting, and transport of proteins to intra- and extra-cellular compartments. In plants, it has the additional task of assembling and exporting the non-cellulosic polysaccharides of the cell wall matrix including pectin and hemicelluloses, which are important for plant development and protection. In this review, we focus on the biosynthesis of complex polysaccharides of the primary cell wall of eudicotyledonous plants. We present and discuss the compartmental organization of the Golgi stacks with regards to complex polysaccharide assembly and secretion using immuno-electron microscopy and specific antibodies recognizing various sugar epitopes. We also discuss the significance of the recently identified Golgi-localized glycosyltransferases responsible for the biosynthesis of xyloglucan (XyG) and pectin.

Idiopathic inflammatory myopathies (IIMs) are severe autoimmune diseases with poorly understood pathogenesis and unmet medical needs. Here, we examine the role of interferon γ (IFNγ) using NOD female mice deficient in the inducible T cell co-stimulator (Icos), which have previously been shown to develop spontaneous IFNγ-driven myositis mimicking human disease. Using muscle proteomic and spatial transcriptomic analyses we reveal profound myofiber metabolic dysregulation in these mice. In addition, we report muscle mitochondrial abnormalities and oxidative stress in diseased mice. Supporting a pathogenic role for oxidative stress, treatment with a reactive oxygen species (ROS) buffer compound alleviated myositis, preserved muscle mitochondrial ultrastructure and respiration, and reduced inflammation. Mitochondrial anomalies and oxidative stress were diminished following anti-IFNγ treatment. Further transcriptomic analysis in IIMs patients and human myoblast in vitro studies supported the link between IFNγ and mitochondrial dysfunction observed in mice. These results suggest that mitochondrial dysfunction, ROS and inflammation are interconnected in a self-maintenance loop, opening perspectives for mitochondria therapy and/or ROS targeting drugs in myositis.

Root border cells (BCs) and their associated secretions form a protective structure termed the root extracellular trap (RET) that plays a major role in root interactions with soil borne microorganisms. In this study, we investigated the release and morphology of BCs of Glycine max using light and cryo-scanning electron microscopy (SEM). We also examined the occurrence of cell-wall glycomolecules in BCs and secreted mucilage using immunofluorescence microscopy in conjunction with anti-glycan antibodies. Our data show that root tips released three populations of BCs defined as spherical, intermediate and elongated cells. The mechanism of shedding seemed to be cell morphotype-specific. The data also show that mucilage contained pectin, cellulose, extracellular DNA, histones and two hemicellulosic polysaccharides, xyloglucan and heteromannan. The latter has never been reported previously in any plant root secretions. Both hemicellulosic polysaccharides formed a dense fibrillary network embedding BCs and holding them together within the mucilage. Finally, we investigated the effect of the RET on the interactions of root with the pathogenic oomycete Phytophthora parasitica early during infection. Our findings reveal that the RET prevented zoospores from colonizing root tips by blocking their entry into root tissues and inducing their lysis.

The root extracellular trap (RET) consists of root-associated, cap-derived cells (root AC-DCs) and their mucilaginous secretions, and forms a structure around the root tip that protects against biotic and abiotic stresses. However, there is little information concerning the changes undergone by the RET during droughts, especially for tree species. Morphological and immunocytochemical approaches were used to study the RET of black poplar (Populus nigra L.) seedlings grown in vitro under optimal conditions (on agar-gelled medium) or when polyethylene glycol-mediated (PEG₆₀₀₀—infused agar-gelled medium) was used to mimic drought conditions through osmotic stress. Under optimal conditions, the root cap released three populations of individual AC-DC morphotypes, with a very low proportion of spherical morphotypes, and equivalent proportions of intermediate and elongated morphotypes. Immunolabeling experiments using anti-glycan antibodies specific to cell wall polysaccharide and arabinogalactan protein (AGP) epitopes revealed the presence of homogalacturonan (HG), galactan chains of rhamnogalacturonan-I (RG-I), and AGPs in root AC-DC cell walls. The data also showed the presence of xylogalacturonan (XGA), xylan, AGPs, and low levels of arabinans in the mucilage. The findings also showed that under osmotic stress conditions, both the number of AC-DCs (spherical and intermediate morphotypes) and the total quantity of mucilage per root tip increased, whereas the mucilage was devoid of the epitopes associated with the polysaccharides RG-I, XGA, xylan, and AGPs. Osmotic stress also led to reduced root growth and increased root expression of the P5CS2 gene, which is involved in proline biosynthesis and cellular osmolarity maintenance (or preservation) in aerial parts. Together, our findings show that the RET is a dynamic structure that undergoes pronounced structural and molecular remodeling, which might contribute to the survival of the root tip under osmotic conditions.

Laminarans are of interest because they have been shown to induce various immune responses in animals and plants. These β-D-glucans differ from each other by their branching rate, which is possibly responsible for their biological activities. In the present study, we characterized a laminaran fraction extracted from Laminaria hyperborea and named LAM2 using sugar composition and structural analyses (NMR). Then, we evaluated its activity as a potential plant elicitor in vitro on tomato seedlings using gene expression analysis and cell wall immunofluorescence labeling. Our study showed that LAM2 isolated from L. hyperborea is a succinylated laminaran which significantly enhanced the plant defense of tomato seedlings and induced cell wall modifications, suggesting a higher elicitor activity than the laminaran standard extracted from Laminaria digitata.

There is a growing demand for molecules of natural origin for biocontrol and biostimulation, given the current trend away from synthetic chemical products. Leachates extracted from plantain stems were obtained after biodegradation of the plant material. To characterize the leachate, quantitative determinations of nitrogen, carbon, phosphorus, and cations (K⁺, Ca²⁺, Mg²⁺, Na⁺), Q2/4, Q2/6, and Q4/6 absorbance ratios, and metabolomic analysis were carried out. The potential role of plantain leachates as fungicide, elicitor of plant defense, and/or plant biostimulant was evaluated by agar well diffusion method, phenotypic, molecular, and imaging approaches. The plant extracts induced a slight inhibition of fungal growth of an aggressive strain of Colletotrichum gloeosporioides, which causes anthracnose. Organic compounds such as cinnamic, ellagic, quinic, and fulvic acids and indole alkaloid such as ellipticine, along with some minerals such as potassium, calcium, and phosphorus, may be responsible for the inhibition of fungal growth. In addition, jasmonic, benzoic, and salicylic acids, which are known to play a role in plant defense and as biostimulants in tomato, were detected in leachate extract. Indeed, foliar application of banana leachate induced overexpression of LOXD, PPOD, and Worky70-80 genes, which are involved in phenylpropanoid metabolism, jasmonic acid biosynthesis, and salicylic acid metabolism, respectively. Leachate also activated root growth in tomato seedlings. However, the main impact of the leachate was observed on mature plants, where it caused a reduction in leaf area and fresh weight, the remodeling of stem cell wall glycopolymers, and an increase in the expression of proline dehydrogenase.