Echinococcus multilocularis serpin regulates macrophage polarization and reduces gut dysbiosis in colitis.

Helminths serve as principal regulators in modulating host immune responses, and their excretory-secretory proteins are recognized as potential therapeutic agents for inflammatory bowel disease. Nevertheless, our comprehension of the mechanisms underlying immunoregulation remains restricted. This investigation delves into the immunomodulatory role of a secretory protein serpin (Emu-serpin), within the larval stage of Echinococcus multilocularis. Our observations indicate that Emu-serpin effectively alleviates dextran sulfate sodium-induced colitis, yielding a substantial reduction in immunopathology and an augmentation of anti-inflammatory cytokines. Furthermore, this suppressive regulatory effect is concomitant with the reduction of gut microbiota dysbiosis linked to colitis, as evidenced by a marked impediment to the expansion of the pathobiont taxa Enterobacteriaceae. In vivo experiments demonstrate that Emu-serpin facilitates the expansion of M2 phenotype macrophages while concurrently diminishing M1 phenotype macrophages, alongside an elevation in anti-inflammatory cytokine levels. Subsequent in vitro investigations involving RAW264.7 and bone marrow macrophages reveal that Emu-serpin induces a conversion of M2 macrophage populations from a pro-inflammatory to an anti-inflammatory phenotype through direct inhibition. Adoptive transfer experiments reveal the peritoneal macrophages induced by Emu-serpin alleviate colitis and gut microbiota dysbiosis. In summary, these findings propose that Emu-serpin holds the potential to regulate macrophage polarization and maintain gut microbiota homeostasis in colitis, establishing it as a promising candidate for developing helminth therapy for preventing inflammatory diseases.

Identification and characteristics of a novel cecropin from the armyworm, Mythimna separata.

BACKGROUND: The recent emergence of antibiotic-resistant strains of bacteria has increased the need to develop effective alternatives to antibiotics. Antimicrobial peptides have been considered as a promising product with several advantages. RESULTS: In this present study, we identified a novel cecropin from the armyworm, Mythimna separata (armyworm cecropin 1, AC-1) by transcriptome sequencing and multi-sequence alignment analysis. The AC-1 precursor comprised 63 amino acid residues, containing a conserved cleavage site of the signal peptide, Ala23-Pro24, while the mature AC-1 included 39 amino acid residues. Chemically synthesized AC-1 exhibited low hemolytic activity against chicken red blood cells, low cytotoxicity against swine testis cells, and effective antimicrobial activity against Salmonella, Escherichia coli, Klebsiella pneumonia, and Pseudomonas aeruginosa. Its antimicrobial activity against Salmonella remained after incubation for 1 h at 100 °C or in 250 mM NaCl, KCl, or MgCl2 solution, implying good thermal- and salt-resistant stabilities. The bactericidal effect of AC-1 on E. coli gradually increased with increasing AC-1 concentration, resulting in deformation, severe edema, cytolysis, cell membrane damage, and reducing intracellular electron density. Additionally, recombinant AC-1 protein expressed in E. coli was digested by enterokinase protease to obtain AC-1, which showed similar antimicrobial activity against E. coli to chemically synthesized AC-1. CONCLUSIONS: This study identified a novel antimicrobial peptide that may represent a potential alternative to antibiotics.

Characterization, expression, and functional analysis of polyamine oxidases and their role in selenium-induced hydrogen peroxide production in Brassica rapa.

BACKGROUND: Selenium (Se)-induced phytotoxicity has been linked to oxidative injury triggered by the accumulation of reactive oxygen species (ROS) due to the disturbance of anti-oxidative systems. However, the way Se stress induces hydrogen peroxide (H2 O2 ) production in plants is a long-standing question. Here we identified the role of polyamine oxidase (PAO) in H2 O2 production in the root of Brassica rapa upon Se stress. RESULTS: Studying Se-induced growth inhibition, H2 O2 accumulation, and oxidative injury in the root of Brassica rapa, we found that excessive Se exposure resulted in a remarkable increase in PAO activity. Inhibition of PAO activity led to decreased H2 O2 content and alleviated oxidative injury in the Se-treated root. These results indicated that Se stress induced PAO-dependent H2 O2 production. A total of six BrPAO family members were discovered in the genome of B. rapa by in silico analysis. Se stress pronouncedly upregulated the expression of most BrPAOs and further transient expression analysis proved that it could lead to H2 O2 production. CONCLUSION: These results suggest that Se stress upregulates the expression of a set of BrPAOs which further enhances PAO activity, contributing to H2 O2 generation in roots. © 2019 Society of Chemical Industry.

The Fungicidal Activity of Thymol against Fusarium graminearum via Inducing Lipid Peroxidation and Disrupting Ergosterol Biosynthesis.

Thymol is a natural plant-derived compound that has been widely used in pharmaceutical and food preservation applications. However, the antifungal mechanism for thymol against phytopathogens remains unclear. In this study, we identified the antifungal action of thymol against Fusarium graminearum, an economically important phytopathogen showing severe resistance to traditional chemical fungicides. The sensitivity of thymol on different F. graminearum isolates was screened. The hyphal growth, as well as conidial production and germination, were quantified under thymol treatment. Histochemical, microscopic, and biochemical approaches were applied to investigate thymol-induced cell membrane damage. The average EC50 value of thymol for 59 F. graminearum isolates was 26.3 µg·mL(-1). Thymol strongly inhibited conidial production and hyphal growth. Thymol-induced cell membrane damage was indicated by propidium iodide (PI) staining, morphological observation, relative conductivity, and glycerol measurement. Thymol induced a significant increase in malondialdehyde (MDA) concentration and a remarkable decrease in ergosterol content. Taken together, thymol showed potential antifungal activity against F. graminearum due to the cell membrane damage originating from lipid peroxidation and the disturbance of ergosterol biosynthesis. These results not only shed new light on the antifungal mechanism of thymol, but also imply a promising alternative for the control of Fusarium head blight (FHB) disease caused by F. graminearum.

Thymol Mitigates Cadmium Stress by Regulating Glutathione Levels and Reactive Oxygen Species Homeostasis in Tobacco Seedlings.

Thymol is a famous plant-derived compound that has been widely used in pharmacy due to its antioxidant and antimicrobial properties. However, the modulation of intrinsic plant physiology by thymol remains unclear. It is a significant challenge to confer plant tolerance to Cd (cadmium) stress. In the present study physiological, histochemical, and biochemical methods were applied to investigate thymol-induced Cd tolerance in tobacco (Nicotiana tabacum) seedlings. Thymol was able to alleviate Cd-induced growth inhibition of tobacco seedlings in both dose- and time-dependent manners. Both histochemical detection and in-tube assays suggested that thymol treatment blocked Cd-induced over-generation of reactive oxygen species (ROS), lipid peroxidation, and loss of membrane integrity in both leaves and roots. Thymol decreased Cd-induced cell death that was indicated in vivo by propidium iodide (PI) and trypan blue, respectively. Thymol stimulated glutathione (GSH) biosynthesis by upregulating the expression of γ-glutamylcysteine synthetase 1 (GSH1) in Cd-treated seedlings, which may contribute to the alleviation of Cd-induced oxidative injury. In situ fluorescent detection of intracellular Cd2+ revealed that thymol significantly decreased free Cd2+ in roots, which could be explained by the thymol-stimulated GSH biosynthesis and upregulation of the expression of phyochelatin synthase 1 (PCS1). Taken together, these results suggested that thymol has great potential to trigger plant resistant responses to combat heavy metal toxicity, which may help our understanding of the mechanism for thymol-modulated cell metabolic pathways in response to environmental stimuli.

Cinnamaldehyde Ameliorates Cadmium-Inhibited Root Elongation in Tobacco Seedlings via Decreasing Endogenous Hydrogen Sulfide Production.

Cinnamaldehyde (CA) is natural plant-derived compound that has been highly appreciated for its medicinal properties. However, little information is known about the regulation of plant intrinsic physiology by CA. To address these gaps, physiological, histochemical, and biochemical approaches were applied to investigate CA-facilitated cadmium (Cd) tolerance in the roots of tobacco (Nicotiana tabacum) seedlings. Treatment with CdCl2 at 20 µM for 72 h resulted in the significant decrease in root elongation by 40.39% as compared to control. CA alleviated Cd-inhibited root elongation in dose- and time-dependent manners. The addition of CA at 20 µM induced significant increase in root elongation by 42.58% as compared to Cd treatment alone. CA abolished Cd-induced ROS (reactive oxygen species) accumulation, lipid peroxidation, loss of membrane integrity, cell death, and free Cd2+ accumulation in roots. CA blocked the Cd-induced increase in the endogenous H2S level through the down-regulation of d-cysteine desulfhydrase (DCD) expression. H2S scavenger hypotaurine (HT) or potent H2S-biosynthetic inhibitor dl-propargylglicine (PAG) were able mimic the action of CA on the blockade of Cd-induced H2S accumulation, cell death, and growth inhibition. Enhancement of the endogenous H2S level with NaHS (H2S donor) abrogated all the beneficial capabilities of CA, HT, and PAG. Collectively, these results suggest that CA has great potential to confer plant tolerance against Cd stress, which is closely associated with its capability to inhibit Cd-induced H2S production. This study not only provides evidences for the regulation of plant physiology by CA but also sheds new light on the cross-talk between CA and H2S in physiological modulations.

Cinnamaldehyde promotes root branching by regulating endogenous hydrogen sulfide.

BACKGROUND: Cinnamaldehyde (CA) has been widely applied in medicine and food preservation. However, whether and how CA regulates plant physiology is largely unknown. To address these gaps, the present study investigated the beneficial effect of CA on root branching and its possible biochemical mechanism. RESULTS: The lateral root (LR) formation of pepper seedlings could be markedly induced by CA at specific concentrations without any inhibitory effect on primary root (PR) growth. CA could induce the generation of endogenous hydrogen sulfide (H2S) by increasing the activity of L-cysteine desulfhydrase in roots. By fluorescently tracking endogenous H2S in situ, it could be clearly observed that H2S accumulated in the outer layer cells of the PR where LRs emerge. Sodium hydrosulfide (H2S donor) treatment induced LR formation, while hypotaurine (H2S scavenger) showed an adverse effect. The addition of hypotaurine mitigated the CA-induced increase in endogenous H2S level, which in turn counteracted the inducible effect of CA on LR formation. CONCLUSION: CA showed great potential in promoting LR formation, which was mediated by endogenous H2S. These results not only shed new light on the application of CA in agriculture but also extend the knowledge of H2S signaling in the regulation of root branching.

[Formulation Optimization of Zuojin Floating-Bioadhesive Pellets by Central Composite Design-Response Surface Methodology].

OBJECTIVE: To optimize the formulation of Zuojin floating-bioadhesive pellets by the central composite design-response surface methodology (CCD-RSM). METHODS: In the formulation design using CCD-RSM, independent variables were the amounts of sodium bicarbonate (X1), HPMC (X2) and MCC (X3) as factors. Small pills roundness, 12 h floating rate and the percentages of in vitro cumulative releases at 2,6 and 12 h were dependent variables. Multilinear and quadratic model were used to estimate the relationship between the dependent and the independent variables. According to best model, the contour plots and RSM were drawn, and the optional formulation was selected. According to the optional formulation,the pellets were prepared and validated. RESULTS: The quadratic was the best fitting mode. Small pills roundness was 15.04 °. 12 h floating rate was 75.07%. Percentages of in vitro cumulation release at 2,6 and 12 h of the option formulation pellets was 27.01%, 70.00% and 84.61%, respectively. The actual value was close to the predicted value. Deviation was less than 5%. CONCLUSION: Quadratic model was preferred in the optimization of formulation due to the statistical confidence. The multi-objective simultaneous optimization of Zuojin floating pellet formulation can be achieved by the central composite design-response surface methodology.

Cinnamaldehyde Inhibits Postharvest Gray Mold on Pepper Fruits via Inhibiting Fungal Growth and Triggering Fruit Defense.

Gray mold infected with Botrytis cinerea frequently appears on fruits and vegetables throughout the supply chain after harvest, leading to economic losses. Biological control of postharvest disease with phytochemicals is a promising approach. CA (cinnamaldehyde) is a natural phytochemical with medicinal and antimicrobial activity. This study evaluated the effect of CA in controlling B. cinerea on fresh pepper fruit. CA inhibited B. cinerea growth in vitro significantly in a dose- (0.1-0.8 mM) and time-dependent (6-48 h) manner, with an EC50 (median effective concentration) of 0.5 mM. CA induced the collapse and breakdown of the mycelia. CA induced lipid peroxidation resulting from ROS (reactive oxygen species) accumulation in mycelia, further leading to cell leakage, evidenced by increased conductivity in mycelia. CA induced mycelial glycerol accumulation, resulting in osmotic stress possibly. CA inhibited sporulation and spore germination resulting from ROS accumulation and cell death observed in spores. Spraying CA at 0.5 mM induced a defense response in fresh pepper fruits, such as the accumulation of defense metabolites (flavonoid and total phenols) and an increase in the activity of defense enzymes (PAL, phenylalanine ammonia lyase; PPO, polyphenol oxidase; POD, peroxidase). As CA is a type of environmentally friendly compound, this study provides significant data on the activity of CA in the biocontrol of postharvest gray mold in peppers.

Interaction between tissue-dwelling helminth and the gut microbiota drives mucosal immunoregulation.

Tissue-dwelling helminths affect billions of people around the world. They are potent manipulators of the host immune system, prominently by promoting regulatory T cells (Tregs) and are generally associated with a modified host gut microbiome. However, the role of the gut microbiota in the immunomodulatory processes for these non-intestinal parasites is still unclear. In the present study, we used an extra-intestinal cestode helminth model-larval Echinococcus multilocularis to explore the tripartite partnership (host-helminth-bacteria) in the context of regulating colonic Tregs in Balb/c mice. We showed that larval E. multilocularis infection in the peritoneal cavity attenuated colitis in Balb/c mice and induced a significant expansion of colonic Foxp3+ Treg populations. Fecal microbiota depletion and transplantation experiments showed that the gut microbiota contributed to increasing Tregs after the helminth infection. Shotgun metagenomic and metabolic analyses revealed that the gut microbiome structure after infection was significantly shifted with a remarkable increase of Lactobacillus reuteri and that the microbial metabolic capability was reprogrammed to produce more Treg cell regulator-short-chain fatty acids in feces. Furthermore, we also prove that the L. reuteri strain elevated in infected mice was sufficient to promote the colonic Treg frequency and its growth was potentially associated with T cell-dependent immunity in larval E. multilocularis infection. Collectively, these findings indicate that the extraintestinal helminth drives expansions of host colonic Tregs through the gut microbes. This study suggests that the gut microbiome serves as a critical component of anti-inflammation effects even for a therapy based on an extraintestinal helminth.

Accumulation and phytotoxicity of microcystin-LR in rice (Oryza sativa).

Irrigation with eutrophic water containing microcystins-LR (MC-LR) poses a potential risk to crops. However, the accumulation of MC-LR in rice grains and the mechanism of MC-LR-induced inhibition in rice roots are not understood. In this study, we detected the accumulation of MC-LR in rice grains collected from Taihu Lake region. MC-LR could accumulate in rice grains, but the risk evaluation suggested that MC-LR levels in rice grains from Taihu Lake region may not pose a threat to human health currently. In addition, MC-LR with low concentrations did not affect the growth of rice roots. However, MC-LR with high concentrations impeded the rice root morphogenesis by inhibiting root elongation, crown root formation, and lateral root development from primordia. Treatment with high concentrations of MC-LR stimulated the production of reactive oxygen species (ROS) and inhibited the production of nitric oxide (NO) in rice roots. Exogenous NO treatment reversed the inhibition of rice root growth under MC-LR stress. These results indicated that ROS and NO played important roles in the development of rice roots in responding to MC-LR stress.

Echinococcosis Is Associated with the Increased Prevalence of Intestinal Blastocystis Infection in Tibetans and Host Susceptibility to the Blastocystis in Mice.

Blastocystis is a common human intestinal protozoan parasite. Little is known about its prevalence in echinococcosis. This study tested whether Echinococcus multilocularis infection would increase host susceptibility to Blastocystis. A total of 114 fecal samples (68 hydatid disease patients and 46 healthy people) were collected from Tibetans in the Qinghai province in China. The presence of Blastocystis was identified by sequencing of the small subunit (SSU) rRNA gene. Balb/c mice were co-infected with Blastocystis and E. multilocularis and tested for host susceptibility to Blastocystis. The overall Blastocystis prevalence was 12.3%; 16.2% in the patients and 4.4% in healthy people (p < 0.05). Sequence analysis identified three known Blastocystis genotypes, including ST1, ST2, and ST3, and one unknown genotype. Experimental dual infection significantly reduced mouse survival rate (20%), induced more severe signs, and increased intestinal damages with a higher intestinal colonization level of Blastocystis. The mouse model showed that E. multilocularis infection increases host susceptibility to Blastocystis. Our study shows a significantly higher prevalence of Blastocystis in patients with liver echinococcosis and reveals that non-intestinal E. multilocularis infection increases host susceptibility to the Blastocystis. Our results highlight that E. multilocularis infection is associated with Blastocystis. These findings remind us that more attention should be paid to the gut health of the patients with a helminth infection during clinical patient care.

Oleanolic Acid Attenuates Morphine Withdrawal Symptoms in Rodents: Association with Regulation of Dopamine Function.

INTRODUCTION: Oleanolic acid (OA) has been shown to be useful for the treatment of mental disorders. METHODS: In this study, we investigated the effects of OA in animal models of spontaneous withdrawal and naloxone-precipitated withdrawal and evaluated the effects of OA on the acquisition, extinction, and reinstatement of morphine-induced conditioned place preference (CPP). RESULTS: OA significantly improved symptoms of withdrawal, and significantly reduced the acquisition and reinstatement of morphine-induced conditioned place preference. Moreover, OA significantly reduced the serum content of 5-hydroxy tryptamine (5-HT) and dopamine (DA) in a dose-dependent manner, and reduced norepinephrine (NE) and 5-HT content in the frontal cortex (PFC), while significantly increasing endorphin content in rats. OA also significantly reduced serum DA content in mice. CONCLUSION: These results indicate that OA can improve the withdrawal symptoms of rats and mice by regulating the DA system and suggest that OA may be useful in treatment of morphine addiction.

Topical gel based nanoparticles for the controlled release of oleanolic acid: design and in vivo characterization of a cubic liquid crystalline anti-inflammatory drug.

BACKGROUND: Oleanolic acid (OA) has multiple pharmaceutical applications including anti-inflammatory activity, but low permeability of the molecule limits its widespread use. METHODS: A cubic liquid crystalline nanoparticle (LCNP)-based gel was prepared as a potential topical delivery system for OA. The LCNP-based gel was optimized using rheological, drug release kinetic, and ex vivo permeation studies. RESULTS: The studies showed that the OA was trapped in the interior of the LCNP with a crystal form of Pn3m space. The optimized LCNP formulation performed well using in vitro release studies for up to 12 h (85.49 ± 0.21%). Ex vivo permeation studies showed that the LCNP-based gel formulation was superior to a standard gel formulation. The r2 value from the Peppas equation indicated good linearity, but showed irregular (non-Fickian) diffusion, suggesting that drug release was controlled by multiple processes. CONCLUSIONS: In this study, OA-loaded LCNPs were prepared by the precursor method, resulting in a well-characterized OA-LCNP gel preparation. The gel was shown to be effective in a rodent carrageenan-induced hind paw inflammation model with sustained efficacy after a single application.

Antifungal activity of the osthol derivative JS-B against Phytophthora capsici.

JS-B (C(12)H(10)O(3)) is a derivative compound of osthol. The antifungal properties of JS-B were tested against 10 economically important plant pathogens. JS-B was effective in inhibiting the mycelial growth of Phytophthora capsici, and its inhibition on different stages of the life cycle of P. capsici was observed. The 50% effective concentration (EC(50)) of JS-B on mycelial dry weight and zoospore germination of P. capsici was 43.74 and 86.03 microg/ml, respectively. The rupture of released zoospores induced by JS-B was reduced by the addition of 100 mM glucose. The ultrastructural study showed that JS-B caused destruction of most of the mitochondrions, the concentration of cell nuclear, and the existing vesicles. When compared with dimethomorph, the activity of JS-B on P. capsici was determined under pot conditions. The result showed that JS-B has a curative effect on pepper blight.

[Mechanism of thymol inhibiting Botrytis cinerea: PAO-H2O2 system]. / éºé¦™è‰é šæŠ‘åˆ¶ç°éœ‰èŒçš„ä½œç”¨æœºç†: PAO-H2O2系统.

Gray mold disease caused by Botrytis cinerea infection is one of the major crop diseases. The application of environmental-friendly fungicides to control gray mold disease has been drawing great attention. Thymol, a natural compound, showed strong antifungal activity against Botrytis cinerea. We investigated the role of polyamine oxidase (PAO)-dependent hydrogen peroxide (H2O2) production in thymol-inhibited B. cinerea growth by using physiological and biochemical approaches. The results showed that: 1) Thymol significantly inhibited the growth of B. cinerea, with remarkable increases in H2O2 content, malondialdehyde (MDA) content, and PAO activity in mycelium. 2) Inhibition of PAO activity (addition of specific inhibitor MDL, N,N'-butanedienyl butanediamine) resulted in significant decreases in the contents of H2O2 and MDA as well as the partial recovery of mycelial growth under thymol treatment, suggesting that thymol might trigger PAO-dependent H2O2 accumulation resulting in oxidative injury and thus inhibit the growth of mycelium. 3) A PAO homologue gene BcPAO was cloned from B. cinerea. Multi-alignment combined with phylogenetic analysis showed that BcPAO protein had typical conserved domain of PAO family members. 4) Thymol at low concentrations did not affect the transcriptional level of BcPAO. However, the transcription of BcPAO was up-regulated remarkably by thymol at high concentration. This suggested that thymol-stimulated PAO activity may be resulted from the regulation of BcPAO. We conclude that oxidative injury caused by PAO-dependent H2O2 production is one of the possible antifungal modes of thymol against B. cinerea. The antifungal mode of thymol found in this study may provide basis for the application of environmental-friendly fungicides.

Efficacy of osthol, a potent coumarin compound, in controlling powdery mildew caused by Sphaerotheca fuliginea.

The efficacy of osthol, a natural coumarin compound, in controlling powdery mildew was evaluated in 2004-2005 in Anhui and Hebei Provinces of China. In both years, the treatments (osthol 15.0 and 18.0 g ai ha(- 1)) showed a stable control efficiency of 75.42, 81.24% and 76.36, 84.84%, respectively, at the Institutes of Plant Protection of Hebei Academy of Agricultural Sciences. In field experiments, osthol was as effective as difenoconazole in controlling powdery mildew and was more effective than triadimefon against Sphaerotheca fuliginea. Protection was expressed as a significant reduction (up to 87% compared with the control) in the mildewed leaf area in young pumpkin plants. Osthol strongly inhibited spore germination and mycelial growth of S. fuliginea in vitro, damaged the cell wall and the organelles of the pathogen. At 48 h after incubation, 50 microg ml(- 1) osthol could completely inhibit spore germination. These findings suggested that the effect of osthol on powdery mildew may be associated with the direct fungitoxic property against the pathogen. We conclude that osthol would be an attractive natural compound for practical agronomic use against powdery mildew.

Lysis of Microcystis aeruginosa with extracts from Chinese medicinal herbs.

Boiling water extracts of 66 selected Chinese medicinal herbs were screened for their anticyanobaterial activity against Microcystis aeruginosa by the soft-agar overlayer (SAO) method. Results indicated that extracts from 16 materials could inhibit the growth of this bacterial species. Among these anticyanobacterial samples, eight extracts showed low minimum inhibitory concentrations (MIC), including four extracts with MICs between 1 and 6 mg/mL, and four extracts with MICs < 1 mg/mL which could be considered useful to prevent the outbreak of cyanobacteria before the appearance of cyanobacterial blooms. Further study showed that three extracts with MIC values < 1 mg/mL induced intensive chlorophyll-a lysis within 7 days at the MIC. The results suggested that highly efficient anticyanobacterial compounds must be involved in the inhibitory activities. The final results indicated these three extracts (from Malaphis chinensis, Cynips gallae-tinctoriae and Fructus mume) had the potential to be developed as algicides due to their remarkably anticyanobacterial activities.

Melatonin facilitates lateral root development by coordinating PAO-derived hydrogen peroxide and Rboh-derived superoxide radical.

Melatonin, a phytochemical, can regulate lateral root (LR) formation, but the downstream signaling of melatonin remains elusive. Here we investigated the roles of hydrogen peroxide (H2O2) and superoxide radical (O2•‾) in melatonin-promoted LR formation in tomato (Solanum lycopersicum) roots by using physiological, histochemical, bioinformatic, and biochemical approaches. The increase in endogenous melatonin level stimulated reactive oxygen species (ROS)-dependent development of lateral root primordia (LRP) and LR. Melatonin promoted LRP/LR formation and modulated the expression of cell cycle genes (SlCDKA1, SlCYCD3;1, and SlKRP2) by stimulating polyamine oxidase (PAO)-dependent H2O2 production and respiratory burst oxidase homologue (Rboh)-dependent O2•‾ production, respectively. Screening of SlPAOs and SlRbohs gene family combined with gene expression analysis suggested that melatonin-promoted LR formation was correlated to the upregulation of SlPAO1, SlRboh3, and SlRboh4 in LR-emerging zone. Transient expression analysis confirmed that SlPAO1 was able to produce H2O2 while SlRboh3 and SlRboh4 were capable of producing O2•‾. Melatonin-ROS signaling cassette was also found in the regulation of LR formation in rice root and lateral hyphal branching in fungi. These results suggested that SlPAO1-H2O2 and SlRboh3/4-O2•‾ acted as downstream of melatonin to regulate the expression of cell cycle genes, resulting in LRP initiation and LR development. Such findings uncover one of the regulatory pathways for melatonin-regulated LR formation, which extends our knowledge for melatonin-regulated plant intrinsic physiology.

Fusarium graminearum growth inhibition due to glucose starvation caused by osthol.

The effects of osthol, a plant coumarin, on morphology, sugar uptake and cell wall components of Fusarium graminearum were examined in vitro by electron microscopy,(14)C-labelling and enzyme activity detection. The results revealed that osthol could inhibit the hypha growth of F. graminearum by decreasing hyphal absorption to reducing sugar. After treatment with 100 microg.mL(-1) osthol for 24 h, many hyphal fragments of F. graminearum appeared. Microscopy observation showed that the cell walls of hyphal fragments blurred and the organelles of the cells degraded with the increasing vacuoles. The N-acetyl-D-glucosamine contents and chitinase activity both increased when hypha were treated with 100 microg.mL(-1) osthol, whereas the activity of beta-1,6-glucanase remained unchanged. When F. graminearum fed with (14)C glucose was treated with 100 microg.mL(-1)osthol, glucose contents decreased to the lowest level, while the contents in non-osthol treated controls remained unchanged. These results suggested that chitinase activity might be related to glucose starvation under osthol treatment, and that the appearance of hyphae fragments maybe the results of the promoted chitinase activity which itself triggered chitin degradation.