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This study investigated whether two exopolysaccharides could serve as exogenous carbon sources to enhance fermentation quality in oat silage, providing a theoretical foundation for their future application in silage. The oats were harvested at the heading stage and, following a period of wilting, were chopped into 2–3 cm lengths for the ensiling experiment. The treatments applied were as follows: (1) a control group (CK), which received only sterile water; (2) a group with added dextran (D); and (3) a group with added levan (L). The fermentation process was monitored at various intervals: 3, 7, 14, 30 and 60 days (d), respectively. Following 60 days of ensiling, the silage was subjected to a 5‐day period of aerobic exposure (AE). EPS changed the fermentation quality of silage, altered the composition of the bacterial community, and had an impact on the feature dissimilarity between sample groups. Meanwhile, EPS showed different regulatory effects on carbohydrate metabolism at different fermentation times. EPS treatment increased the lactic acid content and decreased the pH of silage. After 60 days of fermentation, the treatment also increased the relative abundance of Lactobacillus. Dextran and levan increased the relative abundance of Hafnia–Obesumbacterium and Sediminibacterium, respectively. Under the treatment of dextran, silage retained more WSC content and achieved higher aerobic stability. Upon comparing the bacterial correlation networks, it became evident that the fermentation time altered the composition of inter‐bacterial correlations. In conclusion, EPS can effectively enhance the fermentation quality of oat silage, with dextran yielding the most pronounced positive effects. Bacterial extracellular polysaccharides can serve as an external carbon source to provide additional substrates for microbial fermentation in oat silage.

Background and Objectives: The development of non-dairy probiotic products is a challenge for the food industry, while cereals, as probiotic carriers, provide the means to incorporate probiotics, prebiotics, and fiber into the human diet. The present study investigated the effects of Lactococcus cremoris spp. immobilized on oat flakes on blood and urine biomarkers in a randomized placebo-controlled single-blind clinical trial. Materials and Methods: Fifty-four eligible participants were randomized into a placebo or probiotic group that consumed 5 g of oat flakes daily for 12 weeks. Blood and urine samples were collected at the baseline, 6 weeks, and 12 weeks to assess the glycemic, lipemic, inflammatory, immunological, and antioxidant biomarkers, as well as the vitamin levels. Results: The intervention group exhibited a significant reduction in their hs-CRP levels (p = 0.002) and a trend toward decreased IL-6 levels (p = 0.035) at week 12 compared to the control group, suggesting a potential anti-inflammatory effect. Additionally, a significant reduction in insulin levels was observed in the probiotic group at week 6, with a clinical trend toward differentiation despite the absence of statistically significant differences between the groups. Furthermore, there were promising results regarding certain biomarkers, such as vitamin B12 and cortisol levels, in the probiotic group. Conclusions: The twelve-week consumption of Lactococcus cremoris spp. immobilized on oat flakes resulted in improvements in inflammatory, metabolic, and stress-related biomarkers. These results support the examined concept of non-dairy probiotic products, though further research is needed to confirm their efficacy and clarify their underlying mechanisms.

Like all higher organisms, plants have evolved in the context of a microbial world, shaping both their evolution and their contemporary ecology. Interactions between plant roots and soil microorganisms are critical for plant fitness in natural environments. Given this co-evolution and the pivotal importance of plant–microbial interactions, it has been hypothesized, and a growing body of literature suggests, that plants may regulate the composition of their rhizosphere to promote the growth of microorganisms that improve plant fitness in a given ecosystem. Here, using a combination of comparative genomics and exometabolomics, we show that pre-programmed developmental processes in plants ( Avena   barbata ) result in consistent patterns in the chemical composition of root exudates. This chemical succession in the rhizosphere interacts with microbial metabolite substrate preferences that are predictable from genome sequences. Specifically, we observed a preference by rhizosphere bacteria for consumption of aromatic organic acids exuded by plants (nicotinic, shikimic, salicylic, cinnamic and indole-3-acetic). The combination of these plant exudation traits and microbial substrate uptake traits interact to yield the patterns of microbial community assembly observed in the rhizosphere of an annual grass. This discovery provides a mechanistic underpinning for the process of rhizosphere microbial community assembly and provides an attractive direction for the manipulation of the rhizosphere microbiome for beneficial outcomes. Using comparative genomics and exometabolomics, the authors characterize the chemical composition of plant root exudates and show that this chemical succession is a likely driver of microbial community assembly in the rhizosphere.

Grafting is possible in both animals and plants. Although in animals the process requires surgery and is often associated with rejection of non-self, in plants grafting is widespread, and has been used since antiquity for crop improvement 1 . However, in the monocotyledons, which represent the second largest group of terrestrial plants and include many staple crops, the absence of vascular cambium is thought to preclude grafting 2 . Here we show that the embryonic hypocotyl allows intra- and inter-specific grafting in all three monocotyledon groups: the commelinids, lilioids and alismatids. We show functional graft unions through histology, application of exogenous fluorescent dyes, complementation assays for movement of endogenous hormones, and growth of plants to maturity. Expression profiling identifies genes that unify the molecular response associated with grafting in monocotyledons and dicotyledons, but also gene families that have not previously been associated with tissue union. Fusion of susceptible wheat scions to oat rootstocks confers resistance to the soil-borne pathogen Gaeumannomyces graminis . Collectively, these data overturn the consensus that monocotyledons cannot form graft unions, and identify the hypocotyl (mesocotyl in grasses) as a meristematic tissue that allows this process. We conclude that graft compatibility is a shared ability among seed-bearing plants. Intra- and inter-specific grafting is possible in most orders of monocotyledonous plants, and this process could be used to combat diseases that affect crops, such as Panama disease in bananas.

It is well known that rhizosphere microbiomes differ from those of surrounding soil, and yet we know little about how these root-associated microbial communities change through the growing season and between seasons. We analyzed the response of soil bacteria to roots of the common annual grass Avena fatua over two growing seasons using high-throughput sequencing of 16S rRNA genes. Over the two periods of growth, the rhizosphere bacterial communities followed consistent successional patterns as plants grew, although the starting communities were distinct. Succession in the rhizosphere was characterized by a significant decrease in both taxonomic and phylogenetic diversity relative to background soil communities, driven by reductions in both richness and evenness of the bacterial communities. Plant roots selectively stimulated the relative abundance of Alphaproteobacteria , Betaproteobacteria , and Bacteroidetes but reduced the abundance of Acidobacteria , Actinobacteria , and Firmicutes . Taxa that increased in relative abundance in the rhizosphere soil displayed phylogenetic clustering, suggesting some conservation and an evolutionary basis for the response of complex soil bacterial communities to the presence of plant roots. The reproducibility of rhizosphere succession and the apparent phylogenetic conservation of rhizosphere competence traits suggest adaptation of the indigenous bacterial community to this common grass over the many decades of its presence. IMPORTANCE We document the successional patterns of rhizosphere bacterial communities associated with a “wild” annual grass, Avena fatua , which is commonly a dominant plant in Mediterranean-type annual grasslands around the world; the plant was grown in its grassland soil. Most studies documenting rhizosphere microbiomes address “domesticated” plants growing in soils to which they are introduced. Rhizosphere bacterial communities exhibited a pattern of temporal succession that was consistent and repeatable over two growing seasons. There are few studies assessing the reproducibility over multiple seasons. Through the growing season, the rhizosphere community became progressively less diverse, likely reflecting root homogenization of soil microniches. Phylogenetic clustering of the rhizosphere dynamic taxa suggests evolutionary adaptation to Avena roots. The reproducibility of rhizosphere succession and the apparent phylogenetic conservation of rhizosphere competence traits suggest adaptation of the indigenous bacterial community to this common grass over the many decades of its presence. We document the successional patterns of rhizosphere bacterial communities associated with a “wild” annual grass, Avena fatua , which is commonly a dominant plant in Mediterranean-type annual grasslands around the world; the plant was grown in its grassland soil. Most studies documenting rhizosphere microbiomes address “domesticated” plants growing in soils to which they are introduced. Rhizosphere bacterial communities exhibited a pattern of temporal succession that was consistent and repeatable over two growing seasons. There are few studies assessing the reproducibility over multiple seasons. Through the growing season, the rhizosphere community became progressively less diverse, likely reflecting root homogenization of soil microniches. Phylogenetic clustering of the rhizosphere dynamic taxa suggests evolutionary adaptation to Avena roots. The reproducibility of rhizosphere succession and the apparent phylogenetic conservation of rhizosphere competence traits suggest adaptation of the indigenous bacterial community to this common grass over the many decades of its presence.

Plant–microbe interactions in the rhizosphere have important roles in biogeochemical cycling, and maintenance of plant health and productivity, yet remain poorly understood. Using RNA-based metatranscriptomics, the global active microbiomes were analysed in soil and rhizospheres of wheat, oat, pea and an oat mutant ( sad1 ) deficient in production of anti-fungal avenacins. Rhizosphere microbiomes differed from bulk soil and between plant species. Pea (a legume) had a much stronger effect on the rhizosphere than wheat and oat (cereals), resulting in a dramatically different rhizosphere community. The relative abundance of eukaryotes in the oat and pea rhizospheres was more than fivefold higher than in the wheat rhizosphere or bulk soil. Nematodes and bacterivorous protozoa were enriched in all rhizospheres, whereas the pea rhizosphere was highly enriched for fungi. Metabolic capabilities for rhizosphere colonisation were selected, including cellulose degradation (cereals), H 2 oxidation (pea) and methylotrophy (all plants). Avenacins had little effect on the prokaryotic community of oat, but the eukaryotic community was strongly altered in the sad1 mutant, suggesting that avenacins have a broader role than protecting from fungal pathogens. Profiling microbial communities with metatranscriptomics allows comparison of relative abundance, from multiple samples, across all domains of life, without polymerase chain reaction bias. This revealed profound differences in the rhizosphere microbiome, particularly at the kingdom level between plants.

Glyphosate-based herbicides (GBHs) are widely used for controlling weeds by inhibiting the shikimate pathway. However, the effects of GBH on non-target organisms, such as shikimate pathway-containing microbes, are understudied. Furthermore, the complex interactions between GBH and fertilizers are difficult to predict. Hence, we experimentally investigated the effects of GBH and phosphate fertilizer on the composition of endophytic bacterial communities of potato, faba bean and oat during early and late summer using 16S rRNA gene sequencing, and on plant growth in late summer. GBH treatments significantly affected bacterial communities of early and late summer potato roots and late summer faba bean roots, while phosphate treatments significantly affected bacterial communities of late summer potato leaves, tubers and early summer faba bean leaves. The treatments reduced bacterial diversity in potato and oat and the abundance of putatively beneficial bacteria in potato and faba bean. However, these treatments increased the aboveground biomass of all crops. Thus, agrochemicals had variable effects across crops, tissues and growth stages. While improved crop yield is often prioritized in chemical-intensive farming, the effects of microbiome shifts on crop health need further investigation.

Background The transformation of plant photosynthate into soil organic carbon and its recycling to CO 2 by soil microorganisms is one of the central components of the terrestrial carbon cycle. There are currently large knowledge gaps related to which soil-associated microorganisms take up plant carbon in the rhizosphere and the fate of that carbon. Results We conducted an experiment in which common wild oats ( Avena fatua) were grown in a 13 CO 2 atmosphere and the rhizosphere and non-rhizosphere soil was sampled for genomic analyses. Density gradient centrifugation of DNA extracted from soil samples enabled distinction of microbes that did and did not incorporate the 13 C into their DNA. A 1.45-Mbp genome of a Saccharibacteria (TM7) was identified and, despite the microbial complexity of rhizosphere soil, curated to completion. The genome lacks many biosynthetic pathways, including genes required to synthesize DNA de novo. Rather, it requires externally derived nucleotides for DNA and RNA synthesis. Given this, we conclude that rhizosphere-associated Saccharibacteria recycle DNA from bacteria that live off plant exudates and/or phage that acquired 13 C because they preyed upon these bacteria and/or directly from the labeled plant DNA. Isotopic labeling indicates that the population was replicating during the 6-week period of plant growth. Interestingly, the genome is ~ 30% larger than other complete Saccharibacteria genomes from non-soil environments, largely due to more genes for complex carbon utilization and amino acid metabolism. Given the ability to degrade cellulose, hemicellulose, pectin, starch, and 1,3-β-glucan, we predict that this Saccharibacteria generates energy by fermentation of soil necromass and plant root exudates to acetate and lactate. The genome also encodes a linear electron transport chain featuring a terminal oxidase, suggesting that this Saccharibacteria may respire aerobically. The genome encodes a hydrolase that could breakdown salicylic acid, a plant defense signaling molecule, and genes to interconvert a variety of isoprenoids, including the plant hormone zeatin. Conclusions Rhizosphere Saccharibacteria likely depend on other bacteria for basic cellular building blocks. We propose that isotopically labeled CO 2 is incorporated into plant-derived carbon and then into the DNA of rhizosphere organisms capable of nucleotide synthesis, and the nucleotides are recycled into Saccharibacterial genomes.

Silicon (Si) has been demonstrated to enhance oat resistance to stem rust, caused by Puccinia graminis f. sp. avenae ( Pga ). However, the molecular mechanisms underlying Si-mediated resistance against Pga remain poorly characterized. To address this, we performed transcriptomic and metabolomic analyses on oat plants treated with or without Si and inoculated with Pga . Our results showed that Si treatment increased the activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) under Pga infection, thereby inhibiting reactive oxygen species (ROS) accumulation. Transcriptomic analysis identified 143 differentially expressed genes (55 upregulated, 88 downregulated) in Si-treated plants. Most of these genes were associated with diterpenoid biosynthesis, zeatin biosynthesis, and phenylpropanoid biosynthesis. Metabolomic profiling revealed 69 significantly enriched metabolites, including carbohydrates, organic acids, amino acids, and secondary metabolites. Based on KEGG database annotation, these metabolites were primarily involved in arginine biosynthesis; alanine, aspartate, and glutamate metabolism; cyanoamino acid metabolism; aminoacyl-tRNA biosynthesis; pyrimidine metabolism; and purine metabolism. Integrative analysis of transcriptome and metabolome data indicated that Si treatment significantly altered key metabolic pathways in oat leaves, including tryptophan metabolism, glyoxylate and dicarboxylate metabolism, porphyrin metabolism, and chlorophyll metabolism. Collectively, these findings provide novel molecular insights into Si-mediated enhancement of oat resistance to stem rust.

Saline–alkaline conditions can limit crop productivity and the role of soil microbes in nutrient cycling in arid and semi-arid regions throughout the world. A better understanding of how soil amendments and plant varieties affect rhizosphere microbial communities in saline–alkaline environments is important for the development of sustainable and productive agricultural systems under these challenging conditions. The objective of this study was to determine the effect of organic soil amendments on crop yield, soil physicochemical properties and rhizosphere bacterial communities of two oat cultivars in a saline–alkaline soil. The experiment was conducted in a semi-arid region of Northern China and involved growing two oat cultivars with varying levels of saline–alkaline tolerance under four different amendment treatments: (1) control (no amendments), (2) bio-fertilizer, (3) rotten straw, and (4) combination of bio-fertilizer and rotten straw. The combined bio-fertilizer and rotten straw amendment treatment resulted in the highest oat yields, reduced soil pH, and increased soil salt content for both cultivars. Baiyan2 (tolerant cultivar) had a higher bacterial α-diversity, relative abundance of Proteobacteria and Acidobacteria, and lower relative abundance of Firmicutes compared to Caoyou1 (sensitive cultivar). The rotten straw treatment and combined amendment treatment decreased bacterial α-diversity and the abundance of Proteobacteria , and increased the abundance of Firmicutes , which were positively correlated with soil salt, available nitrogen, phosphorous and potassium for both cultivars. Our study suggested using tolerant oat cultivars with the combined application of rotten straw and bio-fertilizer could be an effective strategy in remediating saline–alkaline soils.