Modern technologies can satisfy human needs only with the use of large quantities of fertilizers and pesticides that are harmful to the environment. For this reason, it is possible to develop new technologies for sustainable agriculture. The process could be carried out by using endophytic microorganisms with a (possible) positive effect on plant vitality. Bacterial endophytes have been reported as plant growth promoters in several kinds of plants under normal and stressful conditions. In this study, isolates of bacterial endophytes from the roots and leaves of Miscanthus giganteus plants were tested for the presence of plant growth-promoting properties and their ability to inhibit pathogens of fungal origin. Selected bacterial isolates were able to solubilize inorganic phosphorus, fix nitrogen, and produce phytohormones, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, and siderophore. Leaf bacterial isolate Pantoea ananat is 50 OL 2 had high production of siderophores (zone ≥ 5 mm), and limited phytohormone production, and was the only one to show ACC deaminase activity. The root bacterial isolate of Pseudomonas libanensis 5 OK 7A showed the best results in phytohormone production (N6-(Δ2-isopentenyl)adenine and indole-3-acetic acid, 11.7 and 12.6 ng·mL-1, respectively). Four fungal cultures-Fusarium sporotrichioides DBM 4330, Sclerotinia sclerotiorum SS-1, Botrytis cinerea DS 90 and Sphaerodes fimicola DS 93-were used to test the antifungal activity of selected bacterial isolates. These fungal cultures represent pathogenic families, especially for crops. All selected root endophyte isolates inhibited the pathogenic growth of all tested fungi with inhibition percentages ranging from 30 to 60%. Antifungal activity was also tested in two forms of immobilization of selected bacterial isolates: one in agar and the other on dextrin-coated cellulose carriers. These results demonstrated that the endophytic Pseudomonas sp. could be used as biofertilizers for crops.
- Publication type
- Journal Article MeSH
Fungicides are commonly used to manage plant pathogens. However, little is known about their effects on the non-target fungal communities that inhabit inside and outside the plant. These fungicides may have adverse effects on beneficial microbial communities with possible consequences for plant health and productivity. Hence, a metagenomic approach, based on the ITS2 region of fungal rDNA, was used to study the impact of foliar application of two fungicides (propineb and iprodione + carbendazim) on non-target tomato leaf fungal communities, in the context of early blight disease management. Metagenomic analysis revealed that the richness and diversity of tomato leaf fungal populations were adversely affected by the chemical treatments tested. Among the two fungicides, propineb (contact fungicide) imparted less non-targeted microorganisms than iprodione + carbendazim (systemic fungicide). In addition, all samples showed association of pathogenic genera Cladosporium, Corynespora, Pseudocercospora along with early blight pathogen Alternaria on tomato leaves that otherwise were undetected. Metagenomic studies also revealed a new mode of action for fungicides and bioagents besides their direct effect that is shifting the microbial community structure so that it provides greater resistance against the pathogen.
- MeSH
- Plant Leaves MeSH
- Metagenomics MeSH
- Mycobiome * MeSH
- Fungicides, Industrial * pharmacology MeSH
- Solanum lycopersicum * MeSH
- Publication type
- Journal Article MeSH
Fungal endophytes have been found to exist in many plant species and appear to be important to their plant hosts. However, the diversity and biological activities of these fungi remain largely unknown. Zanthoxylum simulans Hance, a popular natural spice and medicinal plant, commonly known as Szechuan pepper or Chinese-pepper, grows on Kinmen Island, Taiwan. In this study, leaf and stem samples of Z. simulans, collected in summer and winter, were screened for antimicrobial and anti-inflammatory metabolite-producing endophytic fungi. A total of 113 endophytic strains were isolated and cultured from Z. simulans, among which 23 were found to possess antimicrobial activity, belonging to six fungal genera: Penicillium (26.09%, 6), Colletotrichum (21.74%, 5), Diaporthe (21.74%, 5), Daldinia (17.39%, 4), Alternaria (8.70%, 2), and Didymella (4.34%, 1). We also found that the number of species with antimicrobial activity and their compositions differed between summer and winter. Our study demonstrated that Z. simulans might contain large and diverse communities of endophytic fungi, and its community composition varies seasonally. In addition, fungal endophytes produce antimicrobial agents, which may protect their hosts against pathogens and could be a potential source of natural antibiotics.
This work aimed to evaluate in vitro antagonistic activities and mechanisms of endophytic yeasts against phytopathogenic fungi. A total of 407 yeast strains isolated from tissue of rice, corn, and sugarcane leaves were evaluated for their antagonistic activities against ten phytopathogenic fungi. Only strains of Wickerhamomyces anomalus and Kodamaea ohmeri were found to inhibit the growth of phytopathogenic fungi. Wickerhamomyces anomalus (seven strains) showed antagonistic activity against Curvularia lunata (cause of dirty panicle disease of rice), three Fusarium moniliforme strains (cause of bakanae disease of rice, stalk rot disease of corn, and red rot disease of sugarcane), and Rhizoctonia solani (cause of sheath blight disease of rice). Whereas four Kodamae ohmeri strains inhibited growth of F. moniliforme (cause of bakanae disease of rice). Antagonistic mechanisms of W. anomalus were based on the production of volatile organic compounds (VOCs) (mainly 3-methyl-1-butyl acetate and 3-methyl-1-butanol), fungal cell wall-degrading enzymes (β-1,3-glucanase and chitinase), and siderophores as well as phosphate and zinc oxide solubilization. As for K. ohmeri, the production of VOCs (mainly 3-methyl-1-butanol), β-1,3-glucanase and chitinase were hypothesized as possible mechanisms. The antagonistic activity of W. anomalus against these phytopathogenic fungi and of K. ohmeri against F. moniliforme, and the analysis of the VOCs produced by K. ohmeri are reported for the first time. Two W. anomalus strains, DMKU-RE13 and DMKU-CE52, were evaluated for controlling rice sheath blight disease caused by R. solani in rice plants in the greenhouse and found to suppress the disease 55.2-65.1%, whereas 3% validamycin suppressed this disease by 88.5%.
- MeSH
- Antibiosis * MeSH
- Biological Control Agents MeSH
- Endophytes isolation & purification physiology MeSH
- Fungi growth & development pathogenicity MeSH
- Yeasts isolation & purification physiology MeSH
- Plant Leaves microbiology MeSH
- Plant Diseases economics microbiology prevention & control MeSH
- Crops, Agricultural economics microbiology MeSH
- Publication type
- Journal Article MeSH
- Geographicals
- Thailand MeSH
Phytophthora is arguably one of the most damaging genera of plant pathogens. This pathogen is well suited to transmission via the international plant trade, and globalization has been promoting its spread since the 19th century. Early detection is essential for reducing its economic and ecological impact. Here, a shotgun proteomics approach was utilized for Phytophthora analysis. The collection of 37 Phytophthora isolates representing 12 different species was screened for species-specific peptide patterns. Next, Phytophthora proteins were detected in planta, employing model plants Solanum tuberosum and Hordeum vulgare. Although the evolutionarily conserved sequences represented more than 10% of the host proteome and limited the pathogen detection, the comparison between qPCR and protein data highlighted more than 300 protein markers, which correlated positively with the amount of P. infestans DNA. Finally, the analysis of P. palmivora response in barley revealed significant alterations in plant metabolism. These changes included enzymes of cell wall metabolism, ROS production, and proteins involved in trafficking. The observed root-specific attenuation in stress-response mechanisms, including the biosynthesis of jasmonates, ethylene and polyamines, and an accumulation of serotonin, provided the first insight into molecular mechanisms behind this particular biotic interaction.
- MeSH
- Chromatography, Liquid MeSH
- Stress, Physiological MeSH
- Mass Spectrometry MeSH
- Hordeum enzymology metabolism microbiology MeSH
- Plant Leaves metabolism microbiology MeSH
- Metabolic Networks and Pathways MeSH
- Plant Diseases microbiology MeSH
- Peptides metabolism MeSH
- Phytophthora infestans genetics isolation & purification MeSH
- Polymerase Chain Reaction MeSH
- Proteome metabolism MeSH
- Proteomics MeSH
- Reactive Oxygen Species metabolism MeSH
- Plant Proteins metabolism MeSH
- Solanum tuberosum metabolism microbiology MeSH
- Publication type
- Journal Article MeSH
Citrus black spot (CBS) and post-bloom fruit drop (PFD), caused by Phyllosticta citricarpa and Colletotrichum abscissum, respectively, are two important citrus diseases worldwide. CBS depreciates the market value and prevents exportation of citrus fruits to Europe. PFD under favorable climatic conditions can cause the abscission of flowers, thereby reducing citrus production by 80%. An ecofriendly alternative to control plant diseases is the use of endophytic microorganisms, or secondary metabolites produced by them. Strain LGMF1631, close related to Diaporthe cf. heveae 1, was isolated from the medicinal plant Stryphnodendron adstringens and showed significant antimicrobial activity, in a previous study. In view of the potential presented by strain LGMF1631, and the absence of chemical data for secondary metabolites produced by D. cf. heveae, we decided to characterize the compounds produced by strain LGMF1631. Based on ITS, TEF1, and TUB phylogenetic analysis, strain LGMF1631 was confirmed to belong to D. cf. heveae 1. Chemical assessment of the fungal strain LGMF1631 revealed one new seco-dihydroisocoumarin [cladosporin B (1)] along with six other related, already known dihydroisocoumarin derivatives and one monoterpene [(-)-(1S,2R,3S,4R)-p-menthane-1,2,3-triol (8)]. Among the isolated metabolites, compound 5 drastically reduced the growth of both phytopathogens in vitro and completely inhibited the development of CBS and PFD in citrus fruits and flowers. In addition, compound 5 did not show toxicity against human cancer cell lines or citrus leaves, at concentrations higher than used for the inhibition of the phytopathogens, suggesting the potential use of (-)-(3R,4R)-cis-4-hydroxy-5-methylmellein (5) to control citrus diseases.
- MeSH
- Ascomycota drug effects physiology MeSH
- Citrus microbiology MeSH
- Colletotrichum drug effects physiology MeSH
- Fabaceae microbiology MeSH
- Phylogeny MeSH
- Isocoumarins chemistry metabolism pharmacology MeSH
- Plant Leaves microbiology MeSH
- Plant Diseases microbiology MeSH
- Fruit microbiology MeSH
- Fungicides, Industrial chemistry metabolism pharmacology MeSH
- Saccharomycetales chemistry classification genetics isolation & purification MeSH
- Publication type
- Journal Article MeSH
Pterostilbene (PTE), a dimethylated analogue of resveratrol, mostly contained in Vitis vinifera leaves or in other plant sources is well-known for its antioxidant activity. Due to its bioavailability, low hydrophilicity and thus ability to penetrate hydrophobic biological membranes it was found to be an antimicrobial agent. These properties of PTE offer the possibility of its use in the treatment of microbial infections. The emergence of antibiotic resistance of microorganisms is often caused by their ability to form biofilm; new substances with antibiofilm activity are therefore sought. The representatives of opportunistic pathogenic gram-positive and gram-negative bacteria as well as fungi were used for the determination of minimum inhibitory concentrations (MIC50 and MIC80), minimum biofilm inhibitory concentrations (MBIC50 and MBIC80) and minimum biofilm eradication concentrations (MBEC50 and MBEC80) of PTE and commonly used antibiotics erythromycin, polymyxin B or antimycotic amphotericin B. Total biofilm biomass was investigated by crystal violet staining, and the results were confirmed using microscopic techniques. The most significant antibiofilm action was proved for gram-positive cocci, e.g., MBEC50 of PTE for all strains of Staphylococcus epidermidis tested was 25 mg/L. By contrast, the antibiotic ERM did not exhibit antibiofilm activity in most cases. The permeabilization of cell membranes of gram-positive cocci biofilm by MBIC50 and MBEC50 of PTE was confirmed by LIVE/DEAD staining using spinning disc confocal microscopy. PTE significantly influenced the ability of gram-positive cocci to form biofilm and it effectively eradicated pre-formed biofilm in vitro; its potential for the treatment of biofilm-associated infections of Staphylococcus spp. or Enterococcus faecalis is thus apparent.
- MeSH
- Anti-Bacterial Agents pharmacology MeSH
- Antioxidants pharmacology MeSH
- Biofilms drug effects growth & development MeSH
- Enterococcus faecalis drug effects MeSH
- Gram-Negative Bacteria drug effects MeSH
- Gram-Positive Bacteria drug effects MeSH
- Gram-Positive Cocci drug effects MeSH
- Plant Leaves chemistry MeSH
- Microbial Sensitivity Tests MeSH
- Pseudomonas aeruginosa drug effects MeSH
- Plant Extracts pharmacology MeSH
- Staphylococcus epidermidis drug effects MeSH
- Stilbenes pharmacology MeSH
- Vitis chemistry MeSH
- Publication type
- Journal Article MeSH
Cytokinins are plant hormones with biological functions ranging from coordination of plant growth to the regulation of biotic and abiotic stress-related responses and senescence. The components of the plant immune system can learn from past elicitations by microbial pathogens and herbivores and adapt to new threats. It is known that plants can enter the primed state of enhanced defense induced by either natural or synthetic compounds. While the involvement of cytokinins in defense priming has been documented, no comprehensive model of their action has been provided to date. Here, we report the functional characterization of two aromatic cytokinin derivatives, 6-benzylaminopurine-9-arabinosides (BAPAs), 3-methoxy-BAPA and 3-hydroxy-BAPA, that proved to be effective in delaying senescence in detached leaves while having low interactions with the cytokinin pathway. An RNA-seq profiling study on Arabidopsis leaves treated with 3-methoxy-BAPA revealed that short and extended treatments with this compound shifted the transcriptional response markedly toward defense. Both treatments revealed upregulation of genes involved in processes associated with plant innate immunity such as cell wall remodeling and upregulation of specific MAP kinases, most importantly MPK11, which is a MAPK module involved in stress-related signaling during the pathogen-associated molecular patterns (PAMPs) response. In addition, elevated levels of JA and its metabolites, jasmonate/ethylene-driven upregulation of PLANT DEFENSIN 1.2 (PDF1.2) and other defensins, and also temporarily elevated levels of reactive oxygen species marked the plant response to 3-methoxy-BAPA treatment. Synergistic interactions were observed when plants were cotreated with 3-hydroxy-BAPA and the flagellin-derived bacterial PAMP peptide (flg22), leading to the enhanced expression of the PAMP-triggered immunity (PTI) marker gene FRK1. Our data collectively show that some BAPAs can sensitively prime the PTI responses in a low micromolar range of concentrations while having no observable negative effects on the overall fitness of the plant.
- MeSH
- Arabidopsis chemistry metabolism MeSH
- Arabinonucleosides chemistry pharmacology MeSH
- Cytokinins chemistry pharmacology MeSH
- Plant Immunity drug effects MeSH
- Plant Leaves drug effects MeSH
- MAP Kinase Signaling System drug effects MeSH
- Mitogen-Activated Protein Kinases genetics metabolism MeSH
- Molecular Structure MeSH
- Pathogen-Associated Molecular Pattern Molecules pharmacology MeSH
- Arabidopsis Proteins genetics metabolism MeSH
- Gene Expression Regulation, Plant drug effects MeSH
- Structure-Activity Relationship MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Elevational gradients affect the production of plant secondary metabolites through changes in both biotic and abiotic conditions. Previous studies have suggested both elevational increases and decreases in host-plant chemical defences. We analysed the correlation of alkaloids and polyphenols with elevation in a community of nine Ficus species along a continuously forested elevational gradient in Papua New Guinea. We sampled 204 insect species feeding on the leaves of these hosts and correlated their community structure to the focal compounds. Additionally, we explored species richness of folivorous mammals along the gradient. When we accounted for Ficus species identity, we found a general elevational increase in flavonoids and alkaloids. Elevational trends in non-flavonol polyphenols were less pronounced or showed non-linear correlations with elevation. Polyphenols responded more strongly to changes in temperature and humidity than alkaloids. The abundance of insect herbivores decreased with elevation, while the species richness of folivorous mammals showed an elevational increase. Insect community structure was affected mainly by alkaloid concentration and diversity. Although our results show an elevational increase in several groups of metabolites, the drivers behind these trends likely differ. Flavonoids may provide figs with protection against abiotic stressors. In contrast, alkaloids affect insect herbivores and may provide protection against mammalian herbivores and pathogens. Concurrent analysis of multiple compound groups alongside ecological data is an important approach for understanding the selective landscape that shapes plant defences.
- MeSH
- Alkaloids metabolism MeSH
- Herbivory * MeSH
- Pheromones analysis MeSH
- Ficus chemistry MeSH
- Flavonoids metabolism MeSH
- Insecta physiology MeSH
- Plant Leaves chemistry MeSH
- Altitude * MeSH
- Food Chain * MeSH
- Mammals physiology MeSH
- Biota MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Geographicals
- Papua New Guinea MeSH
The mediator (MED) represents a large, conserved, multi-subunit protein complex that regulates gene expression through interactions with RNA polymerase II and enhancer-bound transcription factors. Expanding research accomplishments suggest the predominant role of plant MED subunits in the regulation of various physiological and developmental processes, including the biotic stress response against bacterial and fungal pathogens. However, the involvement of MED subunits in virus/viroid pathogenesis remains elusive. In this study, we investigated for the first time the gene expression modulation of selected MED subunits in response to five viroid species (Apple fruit crinkle viroid (AFCVd), Citrus bark cracking viroid (CBCVd), Hop latent viroid (HLVd), Hop stunt viroid (HSVd), and Potato spindle tuber viroid (PSTVd)) in two model plant species (Nicotiana tabacum and N. benthamiana) and a commercially important hop (Humulus lupulus) cultivar. Our results showed a differential expression pattern of MED subunits in response to a viroid infection. The individual plant MED subunits displayed a differential and tailored expression pattern in response to different viroid species, suggesting that the MED expression is viroid- and plant species-dependent. The explicit evidence obtained from our results warrants further investigation into the association of the MED subunit with symptom development. Together, we provide a comprehensive portrait of MED subunit expression in response to viroid infection and a plausible involvement of MED subunits in fine-tuning transcriptional reprogramming in response to viroid infection, suggesting them as a potential candidate for rewiring the defense response network in plants against pathogens.
- MeSH
- Species Specificity MeSH
- Humulus genetics virology MeSH
- Plant Leaves genetics microbiology MeSH
- Mediator Complex genetics MeSH
- Gene Expression Regulation, Plant MeSH
- Plant Proteins genetics MeSH
- Plant Viruses MeSH
- Gene Expression Profiling MeSH
- Nicotiana genetics virology MeSH
- Viroids genetics pathogenicity MeSH
- Publication type
- Journal Article MeSH
