Chemical and Biological Technologies in Agriculture最新文献

Background

Nitrogen plays a critical role in sustaining ecosystem functions in peatlands; however, the degradation of approximately 12% of global peatlands substantially alters nitrogen cycling. Although the abundance of stable nitrogen isotopes (δ¹⁵N) has been widely used to trace nitrogen processes, their patterns and implications across degradation gradients are not well understood. This study examined changes in δ¹⁵N and their relationships with nitrogen content and environmental factors along a degradation gradient in alpine peatlands, including flooded wetlands, wet meadows, moderately degraded meadows, and severely degraded meadows.

Results

Soil δ¹⁵N increased from flooded wetlands to wet meadows and moderately degraded meadows, likely due to increased nitrogen release as the peatlands dried. However, soil δ¹⁵N declined from moderately to severely degraded meadows, possibly reflecting reduced microbial activity and limited nitrogen transformation under extreme degradation. Across all sites, roots were depleted in ¹⁵N relative to soil, with increasingly negative Δδ¹⁵N_root–soil values in more degraded sites, likely driven by shifts in plant community composition and changes in nitrogen uptake strategies. Random forest analysis revealed that the soil water content, phosphorus, and nitrogen availability were the primary factors influencing the soil and plant δ¹⁵N values, as did ¹⁵N fractionation during plant nitrogen uptake along the degradation gradient.

Conclusions

Peatland degradation leads to greater soil δ¹⁵N and increased ¹⁵N depletion from soil to plants, indicating a shift toward more open ecosystem nitrogen dynamics and altered plant nitrogen uptake strategies associated with greater nitrogen losses. These findings provide new insights into the impact of peatland degradation on nitrogen dynamics and demonstrate the effectiveness of δ¹⁵N as a tool for monitoring changes in nitrogen cycling and availability across degradation levels.

Graphical Abstract

Background

The application of beneficial microorganisms is an effective solution for the control of crop diseases caused by phytopathogenic bacteria. Bacillus sp. plays a significant role as a biofactory of antimicrobial compounds, and bioformulations containing species of the Bacillus subtilis complex are commercialized. However, there is limited information on the chemical structural diversity of antimicrobial compounds produced by Bacillus nakamurai and its own potential use in agriculture as a suppressor agent of phytopathogenic bacteria.

Results

In this study, the bacterium strain CBAS-959, which produces diffusible black pigmentation in the growth medium, was identified as Bacillus nakamurai through biochemical characterization and the analysis of the 16S rRNA and gyrA genes. Co-culture assays confirmed a strong antagonistic effect against Ralstonia solanacearum and Pectobacterium carotovorum, producing inhibition halos of 23.9 ± 1.8 mm and 23.2 ± 1.8 mm, respectively. The crude extract and pure fractions analyzed by MS/MS mass spectrometry and evaluated by disk diffusion assays demonstrated that B. nakamurai CBAS-959 produces iturin A, bacillibactin, bacillaene, bacillaene B, and dihydrobacillaene, and five isoforms with different surfactin homologs. Extracts obtained from PDB and M1 media showed zones of inhibition of phytopathogenic bacteria between 9.5 ± 0.5 and 23.5 ± 0.5 mm, while fractions of purified compounds between 13.2 ± 0.8 and 21.0 ± 2.6 mm. Bacillibactin showed a MIC of 31.25 µg/mL against R. solanacearum and P. carotovorum but did not inhibit X. citri. PDB-2 L extract was the most active against X. citri, with an MIC of 62.5 µg/mL.

Conclusions

This is the first study that purified and demonstrated that bacillibactin has a direct antibacterial effect against R. solanacearum and P. carotovorum. In addition, this work reports that B. nakamurai CBAS-959 produces bacillaene B, five isoforms of surfactins, inhibits the growth of R. solanacearum on co-culture, and the extracts obtained in PDB and M1 inhibit the growth of X. citri. Therefore, this research provides new information on the metabolic diversity and antimicrobial activity of B. nakamurai CBAS-959 and its potential use for future studies to explore new alternatives for the control of phytopathogens.

Graphical Abstract

Background

HS-2^®Pro, a humic product, is produced from composted thinnings of coniferous trees and is commercially available as a biostimulant. In this study, it was fractionated into humic acid (HA), hydrophobic fulvic acid (FA), hydrophilic FA, and highly hydrophilic FA to identify humic fractions with biostimulant effects. Each fraction was characterized using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, high-performance size-exclusion chromatography (HPSEC), and reversed-phase high-performance liquid chromatography (RP-HPLC) with π–π interactions, and their root elongation-promoting and antioxidant activities were evaluated.

Results

The humic product comprised approximately 70% of its weight on an ash-free basis in the HA fraction, 15% in the hydrophobic FA fraction, 2.5% in the hydrophilic FA fraction, and 4.7% in the highly hydrophilic FA fraction. DRIFT spectroscopy showed that the composition of functional groups varied considerably among the fractions. The estimation of the size distribution of the molecular associations in each fraction by HPSEC indicated that the constituents of the HA fraction are forming larger molecular associations, and the constituents of the FA fractions occur as relatively small aggregates and unbound molecules. The RP-HPLC analysis revealed that each humic fraction was composed of many constituents with different degrees of hydrophilicity/hydrophobicity. The root elongation-promoting activity evaluated from the elongation of the primary roots of komatsuna seedlings was highest in the hydrophilic and highly hydrophilic FA fractions, followed by the HA fraction, whereas the hydrophobic FA fraction showed no significant activity. The antioxidant activity evaluated based on the 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity was higher in the HA and hydrophobic FA fractions and lower in the hydrophilic and highly hydrophilic FA fractions.

Conclusion

The present study revealed that the constituents of the hydrophilic FA, highly hydrophilic FA, and HA fractions were responsible for the root elongation-promoting activity of the humic product, whereas the constituents of the HA and hydrophobic FA fractions were responsible for the antioxidant activity.

Graphical Abstract

Background

Microorganisms can confer or enhance various ecological adaptation functions of host plants, offering wide-ranging applications in the cultivation and production of medicinal plants. While root-associated beneficial actinomycetes are commonly used in biological control, their effects on plant growth and development have been rarely reported. This study focuses on a total of 13 beneficial endophytic actinomycetes in the roots of Salvia miltiorrhiza Bunge. Under different synthetic community (SynCom) construction principles, we constructed five synthetic communities based on functions and relationships to investigate their effects on growth, nitrogen metabolism, phosphorus metabolism, iron metabolism, resistance, and active components of S. miltiorrhiza.

Results

Synthetic communities 3 and 4 composed of functionally complementary strains promoted growth more effectively, synthetic communities 1 and 3 composed of distantly related strains increased total phenolic acid content, and synthetic community 5 that composed solely of indole-3-acetic acid (IAA)-producing strains not only promoted growth but also enhanced the active component content. Genome analysis revealed that synthetic communities with terpenes biosynthetic gene clusters promoted S. miltiorrhiza growth.

Conclusions

Our results suggested synthetic community design should consider strain relationships, plant growth-promoting (PGP) traits, and functional genes. This study introduces novel insights into synthetic community design.

Graphical Abstract

Pyrazines, a widespread class of nitrogen-containing heterocyclic volatiles, are crucial semiochemicals in insect ecology, orchestrating behaviors ranging from alarm signaling and aposematism to aggregation and mate recognition. Despite their recognized importance, significant knowledge gaps persist. The detailed enzymatic pathways for pyrazine biosynthesis—both in insects and their microbial symbionts—remain largely uncharacterized. Furthermore, the precise molecular machinery of pyrazine perception, including the specific olfactory receptors and downstream neural processing, is still not fully understood. To bridge these knowledge gaps, this review consolidates the current understanding of the chemical diversity of pyrazines utilized by insects and delves into their complex biosynthetic origins, covering both de novo insect synthesis and contributions from associated micro-organisms. We explore their varied functional roles in mediating critical insect behaviors and discuss the analytical methodologies used for their study. By outlining these unresolved areas and summarizing the state of the field, this review emphasizes the necessity for integrated investigations to fully elucidate the multifaceted roles of pyrazines. Such comprehensive knowledge is essential for advancing insect biology and for strategically harnessing these compounds in novel, sustainable pest management technologies.

Graphical abstract

Functional diversity of pyrazine compounds in chemical communication

Sub-low soil temperature in spring can cause stress to the apple roots, reducing root function and inhibiting nitrogen (N) uptake. Exogenous sucrose can protect plants from low temperature stress, however, the role of sucrose in regulating the N uptake in apple roots at sub-low temperature is unclear. In this study, the physiological, transcriptional, and metabolic mechanisms of apple root N uptake regulation by 1% sucrose under sub-low root-zone temperature (LT) were evaluated. The results showed that LT treatment significantly inhibited N uptake (especially NO₃⁻-N) and metabolism in roots, decreased photosynthetic and chlorophyll fluorescence in leaves, and inhibited the growth of roots (root activity decreased by 68.85%) and above-ground parts, while exogenous sucrose application significantly alleviated this inhibition. Sucrose application accelerated carbon (C) metabolism and increased sugar, acid, and adenosine triphosphate contents in roots. In addition, exogenous sucrose alleviated the inhibition of N uptake by low temperature, increased the NO₃⁻-N content, and increased the activities of enzymes related to N metabolism (NR, GS, NADH-GOGAT, GPT, and GOT) in roots. Most of the genes associated with C and N metabolism (MdBMY3, MdSS3, MdPFK6, MdCS2, MdNPF4.4, MdGS and MdGDH1) were upregulated under sucrose treatment, as confirmed by transcriptomic data. Furthermore, the transcriptomic and metabolomic results suggested that sucrose may enhance N uptake by increasing the accumulation of luteolin and sinapyl alcohol in flavonoid metabolism. Collectively, these results provided new insights into the role of sucrose in modulating apple root N uptake under sub-low temperature.

Graphical Abstract

Background

Hexavalent chromium [Cr(VI)] is a highly toxic heavy metal that adversely affects plant growth and development. Non-structural carbohydrates (NSCs) serve as dynamic metabolic buffers under environmental stress, balancing growth and detoxification demands. This study elucidates how exogenous citric acid (CA) alters subcellar distribution of Cr(VI) and reprograms NSC allocation to alleviate Cr(VI) toxicity in Oryza sativa through integrated biochemical and transcriptomic analyses.

Results

CA application significantly enhanced biomass growth in Cr(VI)-stressed seedlings, with Cr(VI) redistribution across subcellular compartments and NSC reconfiguration. Tissue-specific transcriptomic shifts revealed CA-mediated modulation of NSC metabolic genes, transporters, and signaling components. Genome-scale metabolic network modeling identified OsNIN4 and OsTPP3 as predicted regulatory nodes to mediate a dynamic equilibrium between NSC partitioning and Cr(VI) detoxification in roots of Cr(VI)-treated rice seedlings supplied with exogenous CA. OsNIN4 suppressed sucrose synthesis to favor nitrogen-based defenses, while OsTPP3 enhanced fructose retention via trehalose-OsSnRK signaling network from “CA + Cr(VI)” treatments. Divergent expression patterns of other NSC-associated genes revealed the multifaceted regulatory mechanism governing NSC metabolism, translocation, and stress-responsive signaling.

Conclusions

Exogenous CA application improved the growth of Cr(VI)-treated rice seedlings. The integrated analysis of genome-scale metabolic network indicated OsNIN4 and OsTPP3 as predicted regulatory nodes for optimizing NSC flux during CA-mediated Cr(VI) detoxification in rice plants.

Graphical Abstract

Background

Chrysanthemum vestitum, a perennial plant in the Compositae family and closely related to Chrysanthemum morifolium, has long been used as both food and medicine. To explore the structural characteristics and potential anti-inflammatory mechanisms of polysaccharides derived from C. vestitum, a homogeneous polysaccharide, CVP_C, was isolated from C. vestitum using hot water extraction and alcohol precipitation. The crude extract was then purified via DEAE-52 cellulose chromatography and gel filtration system. Structural characterization of CVP_C was performed by Fourier-transform infrared (FT-IR) spectroscopy, molecular weight determination, scanning electron microscopy (SEM), monosaccharide composition analysis, thermogravimetric analysis (TGA), nuclear magnetic resonance (NMR) spectroscopy, and methylation analysis. An LPS-induced ALI mouse model was established to assess the protective effects of CVP_C. Inflammatory cytokine levels (IL-6 and TNF-α) in lung tissues and bronchoalveolar lavage fluid (BALF) were quantified, and histopathological changes were evaluated. In addition, gut microbiota profiling was employed to study the underlying mechanisms.

Results

Structural analysis revealed that CVP_C is a xylan-type polysaccharide and has a molecular weight of 25.049 kDa. It is primarily composed of mannose (Man), galactose (Gal), glucosamine (GlcN), glucose (Glc), glucuronic acid (GlcA), xylose (Xyl), rhamnose (Rha), and arabinose (Ara). The backbone structure consisted of → 4)-β-D-Xylp-(1 → residues. In vivo, CVP_C significantly reduced total protein content in BALF and suppressed the expression levels of TNF-α and IL-6 in both BALF and lung tissues, effectively attenuating pulmonary inflammation in the murine model. Histopathological examination and lung injury score further demonstrated inhibition of inflammatory cell infiltration and alleviation of lung tissue injury following CVP_C treatment. Gut microbiota analysis revealed that CVP_C reversed LPS-induced dysbiosis by increasing the relative abundance of Firmicutes while decreasing that of Bacteroidota, thereby ameliorating ALI.

Conclusions

CVP_C is a novel acidic xylan polysaccharide that protects against ALI by reducing pro-inflammatory cytokine secretion and inhibiting inflammatory cell infiltration. Its therapeutic mechanism is likely linked to modulation of gut microbiota composition, promoting beneficial bacteria and suppressing pathogenic taxa. These findings indicate that CVP_C has potential for use as a natural anti-inflammatory agent and functional food ingredient for the promotion of respiratory and gastrointestinal health.

Graphical Abstract