Search Results (81)

The major objective was to investigate the protective capabilities of endophytic bacterial strains isolated from a number of medicinal plant species towards Aspergillus spp. secured from the internal tissues of fungi-infected peanuts. Among 32 fungal isolates surveyed for mycotoxin production in various culture media (PDA, RBCA, YES, CA), 10 isolates qualitatively producing AFB₁, besides 10 OTA-producers, were assayed by HPLC for quantitative toxin production. Aspergillus spp. isolate Be 13 produced an extraordinary quantity of 1859.18 μg mL⁻¹ AFB₁, against the lowest toxin level of 280.40 μg mL⁻¹ produced by the fungus isolate IS 4. The estimated amounts of OTA were considerably lower and fell in the range 0.88–6.00 μg mL⁻¹; isolate Sa 1 was superior, while isolate Be 7 seemed inferior. Based on ITS gene sequencing, the highly toxigenic Aspergillus spp. isolates Be 13 and Sa 1 matched the description of A. novoparasiticus and A. ochraceus, respectively, ochraceus, respectively, which are present in GenBank with identity exceeding 99%. According to 16S rRNA gene sequencing, these antagonists labeled Ar6, Ma27 and So34 showed the typical characteristics of Pseudomonas aeruginosa, Bacillus subtilis and Bacillus velezensis, respectively, with similarity percentages of 99–100. The plant growth-promoting activity measurements of the identified endophytes indicated the production of 16.96–80.00 μg/100 mL culture medium of IAA. Phosphate-solubilizing capacity varied among endophytes from 2.50 to 21.38 μg/100 mL. The polysaccharide production pool of bacterial strains ranged between 2.74 and 6.57 mg mL⁻¹. P. aeruginosa Ar6 and B. velezensis successfully produced HCN, but B. subtilis failed. The in vitro mycotoxin biodegradation potential of tested bacterial endophytes indicated the superiority of B. velezensis in degrading both mycotoxins (AFB₁-OTA) with average percentage of 88.7; B. subtilis ranked thereafter (85.6%). The 30-day old peanut (cv. Giza 6) seedlings grown in gnotobiotic system severely injured due to infection with AFB₁/OTA-producing fungi, an effect expressed in significant reductions in shoot and root growth traits. Simultaneous treatment with the endophytic antagonists greatly diminished the harmful impact of the pathogens; B. velezensis was the pioneer, not P. aeruginosa Ar6. In conclusion, these findings proved that several endophytic bacterial species have the potential as alternative tools to chemical fungicides for protecting agricultural commodities against mycotoxin-producing fungi. Full article

Synthetic herbicides such as glyphosate and 2,4-D are widely used in agriculture but can negatively impact non-target organisms, including microorganisms essential for ecological balance. Yeasts associated with pollinating insects play crucial roles in plant–insect interactions, yet their responses to herbicides remain understudied. This study aimed to evaluate the capacity of yeasts isolated from bees and beetles to produce indole-3-acetic acid (IAA), a plant-growth-promoting hormone, as well as their ability to tolerate or degrade glyphosate (in the commercial herbicide Zapp QI 620^®) and 2,4-D (in the commercial Aminol 806^®). Seven yeast strains were isolated from insects, identified via ITS sequencing, and assessed for IAA production in YPD medium. Growth assays were conducted under varying herbicide concentrations, and 2,4-D degradation was analyzed using high-performance liquid chromatography. All strains produced IAA, with Papiliotrema siamensis CHAP-239 exhibiting the highest yield (4.17 mg/L). Glyphosate completely inhibited growth in all strains, while 2,4-D showed dose-dependent effects, with four strains tolerating lower concentrations. Notably, Meyerozyma caribbica CHAP-248 degraded up to 46% of 2,4-D at 6.045 g/L. These findings highlight the ecological risks herbicides pose to beneficial yeasts and suggest the potential of certain strains for bioremediation in herbicide-contaminated environments. Overall, the study underscores the importance of preserving microbial biodiversity in the context of sustainable agriculture. Full article

Toona sinensis (A. Juss.) Roem, classified under the Toona genus of the Meliaceae family, is a fast-growing, woody species endemic to China, valued as both a vegetable crop and medicinal plant. Its seeds achieve rapid germination through a cascade of interconnected physiological, metabolic, and hormonal adaptations. Initially, physiological hydration is driven and accelerated by only two distinct phases of water imbibition. This hydration surge triggers storage reserve mobilization, with soluble sugars, proteins, and lipids undergoing rapid degradation during imbibition, while starch catabolism proceeds gradually—a pattern mirrored by progressive increases in enzymatic activities (amylase, protease, and acid phosphodiesterase (ACP)) that correlate with reserve reallocation. Concurrently, a metabolic shift from glycolysis to the pentose phosphate pathway (PPP) optimizes energy utilization, supporting germination acceleration. These biochemical changes are orchestrated by hormonal coordination: elevated gibberellin A₃ (GA₃), zeatin riboside (ZR), and indole-3-acetic acid (IAA) levels, coupled with rising GA₃/ABA, IAA/ABA, and ZR/ABA ratios, temporally aligned with germination progression. Finally, structural evidence confirms successful germination completion, as cotyledon lipid droplet breakdown and starch granule synthesis directly correlate with embryonic elongation. Together, these mechanisms underscore T. sinensis’ adaptive strategy, integrating physiological plasticity, metabolic flexibility, and endocrine precision to ensure efficient germination. Full article

The fungus Alternaria alternata, which causes tobacco brown spot disease, poses a serious threat to the tobacco industry. Beneficial microorganisms and their secondary metabolites have emerged as a promising green strategy for disease management. This study recovered 16 endophytic bacterial strains from Mentha haplocalyx Briq., a therapeutic herb. The study revealed that strain B5, with an inhibition rate of 82.76%, exhibited the highest antifungal activity against A. alternata. This strain exhibited broad-spectrum antifungal activity, with inhibition rates ranging from 66.34% to 87.23%. Phylogenetic analysis of 16S rDNA and gyrA gene sequences identified it as Bacillus velezensis (GenBank: PV168970 and PV173738). Further characterization revealed that strain B5 can secrete cell wall-degrading enzymes, produce IAA, and synthesize siderophores. The growth of mycelium in A. alternata was greatly reduced by both the ethyl acetate extract and the filtered liquid from the sterile fermentation, resulting in marked morphological abnormalities. Multiple antifungal active substances were identified through liquid LC-MS analysis. Greenhouse experiments demonstrated that the B5 fermentation broth effectively suppressed the occurrence of tobacco brown spot disease, achieving a relative control efficacy of 60.66%, comparable to that of 10% difenoconazole water dispersible granule (WDG). Additionally, strain B5 enhances plant disease resistance by activating the activities of key defense enzymes. B. velezensis B5 serves as a safe alternative to chemical fungicides and is highly effective at controlling tobacco brown spot disease. Full article

Indole-3-acetic acid (IAA) glycosyltransferase (IAGLU) plays vital roles in modulating plant development and responses to environmental cues. Here, we elucidate the regulatory mechanism of OsIAGLU in modulating root gravitropism using OsIAGLU-overexpressing (OE) rice (Oryza sativa L.). OsIAGLU upregulation substantially decreases IAA levels, resulting in the impairment of multiple agronomic traits and root gravitropism, as well as nearly complete suppression of starch granule accumulation in rice root tips. Exogenous application of the auxin analog 1-naphthaleneacetic acid (NAA) effectively rescued both starch granule accumulation and root gravitropism. Starch synthesis genes exhibited relatively stable or slightly decreased expression following NAA treatments, whereas all starch degradation genes displayed a consistent downward trend in expression after NAA treatment. This suggests that starch degradation genes may play a more prominent role in regulating starch granule accumulation in rice roots, contrasting sharply with their roles in Arabidopsis. Moreover, decreased auxin levels perturbed the accumulation and distribution of hydrogen peroxide (H₂O₂) in rice root tips, while NAA treatment restored normal H₂O₂ distribution and accumulation in OE roots. This study clearly demonstrates that auxin not only functions in regulating agronomic traits but also plays an essential role in gravity perception by modulating starch granule accumulation in rice root tips. Full article

This article methodically reveals how, in woody plants (poplar), the interaction between N and P coordinates root structure and nutrient absorption through a complex hormone signaling network. This study bridges a significant gap in our knowledge of nutrient interaction networks. The results demonstrate that NO₃⁻ significantly enhances the gene expression and enzymatic activity of organic acid synthases (MDH, PEPC) and APs. Furthermore, it synergizes with IAA/ABA signals to refine root structure, enhancing the surface area for P absorption. In low Pi availability environments, NO₃⁻ further promotes P recycling by simultaneously boosting the levels of Pi transport proteins (notably, the PHO family), facilitating myo-inositol phosphate metabolism (via IMP3/ITPK1-mediated PP-InsPs degradation), and augmenting IAA/SA signals. Pi induces the activity of N assimilation enzymes (GS/GOGAT/GDH), facilitating nitrogen metabolism. However, in the absence of N, it leads to a metabolic imbalance characterized by high enzymatic activity but low efficiency. Alternatively, adequate N availability allows Pi to improve root robustness and N assimilation efficiency, mediated by IAA/GA accumulation and ABA signaling (e.g., SNRK2/ABF). We propose the existence of an intricate network in poplar, orchestrated by transcriptional cascades, metabolic regulation, and hormonal synergism. Key modules such as SPX-PHR, NLA, HHO2, and MYB59 are likely central to this network’s function. These findings offer a foundational framework for the development of molecular breeding and precise fertilization strategies, enhancing the efficient use of N and P in forestry. Full article

Current management of Ageratina adenophora, a highly invasive weed, relies on synthetic herbicides with environmental and resistance risks, necessitating eco-friendly alternatives. This study evaluated seven phenyl derivatives for phytotoxic activity against A. adenophora via in vitro bioassays. Methyl 4-hydroxyphenylacetate exhibited potent herbicidal efficacy, achieving 100% mortality in 2-month-old seedlings at 30 mM, 3-month-old seedlings at 100 mM, and wild adult/6-month-old plants at 200 mM within 48 h. At 250 mM, the compound reduced CO₂ assimilation by 113.6% and stomatal conductance by 92.2%, indicating severe photosynthetic and transpirational disruption via oxidative stress-mediated chloroplast degradation and stomatal dysfunction. Hormonal profiling revealed significant declines in IAA-ASP, GA1, TZeatin, and TZR, alongside elevated ABA levels, while GA3 remained stable. These hormonal shifts likely drive stomatal closure and metabolic collapse, culminating in plant death. This study provides the first evidence of methyl 4-hydroxyphenylacetate’s dual-action phytotoxicity—targeting both stomatal regulation and hormonal balance—positioning it as a sustainable biocontrol agent for A. adenophora and potentially other invasive weeds. Full article

To increase the seed setting rate and yield of large-panicle rice varieties, one agronomic and breeding strategy is to increase the proportion of spikelets in the middle portion of the panicle as many of the lower spikelets fail to produce grains. Current nitrogen management during panicle development mainly focuses on fertilization at the emergence of the top fourth leaf, which increases the number of secondary branch spikelets on the lower part of the panicle. Two-year field experiments were conducted in 2021 and 2022 with two typical large-panicle hybrid indica rice cultivars, IIYM86 and JLY8612. Nitrogen was applied at the emergence of the top fifth (TL5), fourth (TL4), third (TL3), and second (TL2) leaves, with no nitrogen application as a control. This study aimed to investigate the effects of nitrogen application on the panicle structure, seed setting rate, and grain yield at different stages of panicle development. Nitrogen application at TL3 achieved the highest grain yield, followed by application at TL4, for both cultivars over the two years. TL3 did not significantly alter the number of spikelets per panicle but increased the proportion of spikelets located in the middle part of the panicle and reduced the proportions in the upper and lower parts compared to TL4. These effects were attributed to a significant increase in secondary branch spikelet differentiation in the middle part and a decrease in secondary branch spikelet differentiation in the upper and lower parts. Compared to TL4, TL3 significantly increased the seed setting rate by 9.46 and 9.48% and the grain yield by 6.86 and 8.92% in IIYM86 and JLY8612, respectively. In TL3, the significant increase in secondary branch spikelet differentiation in the middle part was primarily due to significantly reduced indole acetic acid (IAA) and an increased cytokinin/IAA ratio, which inhibited apical dominance. The significant decrease in secondary branch spikelet differentiation in the lower part of TL3 was mainly related to a significant increase in IAA and a reduction in the cytokinin/IAA ratio. Transcriptome analysis of young panicles confirmed these results, and differentially expressed genes between TL3 and TL4 were primarily enriched in plant hormone signal transduction related to IAA biosynthesis and degradation. These findings indicate that postponing nitrogen application until TL3 can improve the PTI and the seed setting rate by regulating hormonal balance, thereby optimizing nitrogen management during panicle development in large-panicle hybrid indica rice cultivars. Full article

The rhizosphere microbiota of arid plants plays a crucial role in adaptation to environmental stress. However, few studies have characterized microorganisms associated with Agave species and their contribution to resilience against salinity and drought. This study aimed to isolate and characterize halotolerant bacteria from the rhizosphere of Agave potatorum Zucc from two different sites and evaluate their in vitro Na⁺ sequestration, desiccation resistance, and phytohormone production. These traits were compared with those of halotolerant bacteria isolated from a highly saline soil at a third site. Bacteria were obtained through serial dilutions and cultured on R2A plates supplemented with varying NaCl concentrations. The most efficient Na⁺-sequestering isolates underwent an 18-day desiccation assay, and their production of indole-3-acetic acid (IAA) and gibberellic acid (GA₃) was quantified. Among the 48 halotolerant isolates obtained, 7 (SM1, SM10, SPM5, SM7, SM19, VZ9, and SPM1) exhibited the highest Na⁺ sequestration efficiency. Among these isolates, SM1 exhibited the highest in vitro Na⁺ sequestration capacity (10.74 μg L⁻¹, p < 0.05). SM1 and SPM1 demonstrated the greatest desiccation resistance, at 88.39% and 83.05%, respectively. Additionally, SM7 produced the highest levels of IAA (13.69 μg mL⁻¹, p < 0.05), while SM1 exhibited the highest GA₃ production (1285.38 μg mL⁻¹, p < 0.05). Based on these characteristics, isolates SPM1 and SM1 exhibited the highest efficiency in tolerating drought and salinity stress. However, isolate SPM1 may colonize the rhizosphere of A. potatorum more effectively, likely due to its adaptation as a native isolate to the edaphic and environmental conditions in which this agave thrives. Molecular identification confirmed that the isolates belong to the genera Kosakonia, Priestia, Streptomyces, Bacillus, Stutzerimonas, Pseudomonas, and Exiguobacterium. This study highlights the diversity of halotolerant bacteria in the rhizosphere of A. potatorum and their potential as bioinoculants for enhancing soil fertility and restoring degraded soils. Full article

The cuprizone (CPZ) model of multiple sclerosis (MS) is excellent for studying the molecular differences behind the damage caused by poisoning. Metabolic differences in the kynurenine pathway (KP) of tryptophan (TRP) degradation are observed in both MS and a CPZ mouse model. Our goal was to analyze the kynurenine, serotonin, and indole pathways of TRP degradation on the periphery, in the neurodegenerative processes of inflammation. In our study, mice were fed with 0.2% CPZ toxin for 5 weeks. We examined the metabolites in the three pathways of TRP breakdown in urine, plasma, and relevant visceral organs with bioanalytical measurements. In our analyses, we found a significant increase in plasma TRP, 5-hydroxytryptophan (5-HTP), and indole-3-acetic acid (IAA) levels, while a decrease in the concentrations of 3-hydroxy-L-kynurenine (3-HK), xanthurenic acid (XA), kynurenic acid (KYNA), and quinaldic acid in the plasma of toxin-treated group was found. A marked decrease in the levels of 3-HK, XA, KYNA, quinaldic acid, and indole-3-lactic acid was also observed in the visceral organs by the end of the poisoning. Furthermore, we noticed a decrease in the urinary levels of the TRP, KYNA, and XA metabolites, while an increase in serotonin and 5-hydroxyindoleacetic acid in the CPZ group was noticed. The toxin treatment resulted in elevated tryptamine and indoxyl sulfate levels and reduced IAA concentration. Moreover, the urinary para-cresyl sulfate concentration also increased in the treated group. In the present study, we showed the differences in the three main metabolic pathways of TRP degradation in the CPZ model. We confirmed the relationship and correlation between the content of the kynurenine metabolites in the plasma and the tissues of the visceral organs. We emphasized the suppression of the KP and the activity of the serotonin and indole pathways with a particular regard to the involvement of the microbiome by the indole pathway. Consequently, this is the first study to analyze in detail the distribution of the kynurenine, serotonin, and indole pathways of TRP degradation in the periphery. Full article

In plants, calcium (Ca) serves as an essential nutrient and signaling molecule. Melatonin is a biologically active and multi-functional hormone that plays an important role in improving nutrient use efficiency. However, its involvement in plant responses to Ca deficiency remains largely unexplored. This study aimed to assess the effects of melatonin on Ca absorption, the antioxidant system, and root morphology under low-Ca (LCa) stress conditions, as well as to identify key regulatory factors and signaling pathways involved in these processes using transcriptome analysis. Under LCa conditions, wax gourd seedling exhibited significant decreases in Ca accumulation, showed inhibition of root growth, and demonstrated the occurrence of oxidative damage. However, melatonin application significantly enhanced Ca content in wax gourd seedlings, and it enhanced the absorption of Ca²⁺ in roots by upregulating Ca²⁺ channels and transport genes, including BhiCNGC17, BhiCNGC20, BhiECA1, BhiACA1, and BhiCAX1. Furthermore, the application of exogenous melatonin mitigated the root growth inhibition and oxidative damage caused by LCa stress. This was evidenced by increases in the root branch numbers, root tips, root surface area, and root volume, as well as enhanced root vitality and antioxidant enzyme activities, as well as decreases in the reactive oxygen species content in melatonin treated plants. Transcriptome results revealed that melatonin mainly modulated the brassinosteroids (BRs) and auxin signaling pathway, which play essential roles in root differentiation, elongation, and stress adaptation. Specifically, melatonin increased the active BR levels by upregulating BR6ox (a BR biosynthesis gene) and downregulating BAS1 (BR degradation genes), thereby affecting the BR signaling pathway. Additionally, melatonin reduced IAA levels but activated the auxin signaling pathway, indicating that melatonin could directly stimulate the auxin signaling pathway via an IAA-independent mechanism. This study provides new insights into the role of melatonin in nutrient stress adaptation, offering a promising and sustainable approach to improve nutrient use efficiency in wax gourd and other crops. Full article

Plant growth-promoting bacteria (PGPB) play a role in stimulating plant growth through mechanisms such as the synthesis of the phytohormone indole-3-acetic acid (IAA). The aims of this study were the characterization of IAA synthesis and degradation by the model aromatic-degrading bacterium Paraburkholderia xenovorans LB400, and its growth promotion of the Nicotiana tabacum plant. Strain LB400 was able to synthesize IAA (measured by HPLC) during growth in the presence of tryptophan and at least one additional carbon source; synthesis of anthranilic acid was also observed. RT-PCR analysis indicates that under these conditions, strain LB400 expressed the ipdC gene, which encodes indole-3-pyruvate decarboxylase, suggesting that IAA biosynthesis proceeds through the indole-3-pyruvate pathway. In addition, strain LB400 degraded IAA and grew on IAA as a sole carbon and energy source. Strain LB400 expressed the iacC and catA genes, which encode the α subunit of the aromatic-ring-hydroxylating dioxygenase in the IAA catabolic pathway and the catechol 1,2-dioxygenase, respectively, which may suggest a peripheral IAA pathway leading to the central catechol pathway. Notably, P. xenovorans LB400 promoted the growth of tobacco seedlings, increasing the number and the length of the roots. In conclusion, this study indicates that the versatile bacterium P. xenovorans LB400 is a PGPB. Full article

Nitrilases, found to have a common presence in the plant kingdom, are capable of converting nitriles into their corresponding carboxylic acids through hydrolysis. In Arabidopsis, the nitrilases NIT1, NIT2, and NIT3 catalyze the formation of indole-3-acetonitrile (IAN) into indole-3-acetic acid (IAA). Notably, IAN can originate from the breakdown products of indole glucosinolates. Glucosinolates, which are plant secondary metabolites commonly found in cruciferous plants, and their breakdown products, are crucial for plant defense against pathogens. In our study, we found that nitrilases positively regulate resistance to Pseudomonas syringae pv. tomato DC3000 (PstDC3000) in mature Arabidopsis. Transcriptome data showed that after PstDC3000 treatment, genes related to the auxin pathway in nit1nit2nit3 changed more dramatically than in the wild type. Moreover, the enhancement of disease resistance through exogenous aliphatic glucosinolate application relies on NIT1/2/3. Hence, it is hypothesized that NIT1/2/3 may serve a dual role in disease resistance and defense mechanisms. After infection with PstDC3000, NIT1/2/3 catalyzes the biosynthesis of auxin, thereby triggering certain disease-related responses. On the other hand, NIT1/2/3 can also break down nitriles generated from aliphatic glucosinolate degradation to enhance disease resistance. Our study elucidates the regulatory mechanism of nitrilases in Arabidopsis disease resistance, offering a theoretical foundation for enhancing disease resistance in cruciferous plants. Full article

Wilt and root rot diseases caused by Fusarium species can severely affect herbage plants, resulting in significant losses. Currently, the research and application of biological control methods targeting Fusarium-related diseases in herbage plants are limited. In this study, 11 plant growth-promoting rhizobacterium (PGPR) strains previously screened from alpine grassland were tested to assess their inhibitory effects on Fusarium oxysporum and their ability to produce siderophores, protease, cellulase, and amylase. Meanwhile, their plant growth-promoting properties, such as nitrogenase activity, phosphate dissolution, and IAA production, were determined. The results showed that the tested PGPR strains exhibited diverse functionalities. Nine PGPR strains demonstrated antagonistic effects on colony diameter against Fusarium oxysporum, with Bacillus subtilis gt11 showing the strongest inhibition, followed by Bacillus velezensis gt1 and Bacillus subtilis gtr1, with inhibition rates of 73.57%, 69.13%, and 67.94%, respectively. The test PGPR strains mainly comprised three genera: Pseudomonas, Bacillus, and Acinetobacter. Pseudomonas was the dominant genus. The PGPR strains displayed diverse inhibitory mechanisms. Bacillus velezensis gt1, Pseudomonas subtilis gt11, Bacillus subtilis gtr1, and Pseudomonas tritici gt6 exhibited high levels of siderophore, protease, cellulase, and amylase production, potentially inhibiting Fusarium oxysporum by degrading its cell wall through these enzyme activities. The majority of the tested PGPR strains have the characteristic of producing multiple enzymes. Considering the plant growth-promoting characteristics of nitrogenase activity (38.13–505.70 nmol C₂H₄/vial), phosphate solubilization (inorganophosphates ranging from 41.18 to 91.65 μg·mL⁻¹; organophosphates ranging from 5.21 to 31.17 μg·mL^−l), and IAA secretion (9.27–48.95 μg·mL⁻¹), Bacillus subtilis gt11, Bacillus velezensis gt1, Acinetobacter calcoaceticus gt14, and Bacillus subtilis gtr1 show potential for development into biofertilizers or biocontrol agents. Full article

Seed dormancy and germination are critical factors affecting oil palm production efficiency. The typical dormancy-breaking process involves dry heat treatment (38–40 °C for 40–60 days) followed by germination at 30–32 °C. To understand the molecular mechanisms behind this process and improve germination rates and speed, we conducted transcriptome analysis at three stages: pre-incubation, 45-day incubation at 40 °C, and 14-day germination at 32 °C. Our findings, supported by qRT–PCR and DEGs analysis, identified four key stages: ABA degradation, energy mobilization, starch mobilization, and cell elongation and division. ABA pathway genes (SnRK2, PYR/PYL) were active during dormancy release, while GAE and GPI were upregulated after heat treatment, indicating increased energy metabolism and structural changes. During germination, genes involved in starch/sucrose metabolism (SPS, TPP, SS, MGAM) and cell wall biosynthesis (GAUT1, PE, GAE) supported embryo expansion, with BAM, PGM, GlgB fueling early growth. Auxin (TIR1, AUX/IAA, ARF), brassinosteroid (BRI1, BSK, BIN2, CYCD3), ethylene (ETR, CTR1), and jasmonic acid (JAR1, COI1) pathway genes regulated cell growth and stress response, promoting seedling development. Though gibberellins were not crucial for this oil palm variety, gene expression varied between varieties. This study provides information on oil palm seed germination that could be applied to other oil palm species, particularly in terms of incubation times and chemical treatments. Full article