Plant Pathogenic Fungi Fusarium Oxysporum Research Articles

Down Regulation of Plant Pathogenic Fungus Fusarium Oxysporum by Tree Extracts

Down Regulation of Plant Pathogenic Fungus Fusarium Oxysporum by Tree Extracts

Identification and Antifungal Activity of Compounds from the Mangrove Endophytic Fungus Aspergillus clavatus R7.

Two new coumarin derivatives, 4,4′-dimethoxy-5,5′-dimethyl-7,7′-oxydicoumarin (1), 7-(γ,γ-dimethylallyloxy)-5-methoxy-4-methylcoumarin (2), a new chromone derivative, (S)-5-hydroxy-2,6-dimethyl-4H-furo[3,4-g]benzopyran-4,8(6H)-dione (5), and a new sterone derivative, 24-hydroxylergosta-4,6,8(14),22-tetraen-3-one (6), along with two known bicoumarins, kotanin (3) and orlandin (4), were isolated from an endophytic fungus Aspergillus clavatus (collection No. R7), isolated from the root of Myoporum bontioides collected from Leizhou Peninsula, China. Their structures were elucidated using 1D- and 2D- NMR spectroscopy, and HRESIMS. The absolute configuration of compound 5 was determined by comparison of the experimental and calculated electronic circular dichroism (ECD) spectra. Compound 6 significantly inhibited the plant pathogenic fungi Fusarium oxysporum, Colletotrichum musae and Penicillium italicum, compound 5 significantly inhibited Colletotrichum musae, and compounds 1, 3 and 4 greatly inhibited Fusarium oxysporum, showing the antifungal activities higher than those of the positive control, triadimefon.

Isolation, identification, optimization, and metabolite profiling of Streptomyces sparsus VSM-30

Deep sea sediment samples of Bay of Bengal (Visakhapatnam) have been analyzed for actinomycetes as an elite source to screen for the production of bioactive metabolites. The actinomycetes strain VSM-30 has an exciting bioactivity profile and was isolated during our systemic screening of marine actinomycetes. It was identified as Streptomyces sparsus based on morphological, physiological, biochemical, and molecular approaches. Response surface methodology regression analysis was carried out to fit the experimental data of each response by the second-order polynomial. The results have proven right interaction among process variables at optimized values of incubation time at 12days, pH at 8, temperature at 30°C, concentrations of starch at 1%, and tryptone at 1% and the data have been adequately fitted into the second-order polynomial models. Under these conditions, the responses (zones of inhibition) of plant pathogenic fungi Aspergillus niger, Aspergillus flavus, Fusarium oxysporum, Fusarium solani, and Penicillium citrinum were also matched with experimental and predicted results. Chemotypic analysis of ethyl acetate extract of the strain was done using LC-Q-TOF-MS revealed the presence of bioactive compounds including tryptophan dehydrobutyrine diketopiperazine, maculosin, 7-o-demethyl albocycline, albocycline M-2, and 7-o-demethoxy-7-oxo albocycline in a negative ion mode. The ethyl acetate extract of actinobacterium has been subjected to gas chromatography and mass spectroscopy (GC-MS) revealed the presence of diverse compounds such as dotriacontane, tetracosane 11-decyl-, diheptyl phthalate, 1-hexadecanesulfonyl chloride, L-alanyl-L-tryptophan, phthalic acid ethyl pentyl ester, 4-trifluoroacetoxyhexadecane, and 1H-imidazole 4,5-dihydro-2,4-dimethyl. Hence, the ethyl acetate extract of Streptomyces sparsus VSM-30 may have antibacterial, antifungal, and antioxidant activities due to the presence of secondary metabolites in ethyl acetate extract. The study also supports marine sediment samples of Bay of Bengal, a promising marine ecosystem remained to be explored for new bioactive compounds.

Effectiveness of a full-scale horizontal slow sand filter for controlling phytopathogens in recirculating hydroponics: From microbial isolation to full microbiome assessment

The microbial disinfestation efficiency of an innovative horizontal-flow slow sand filter (HSSF) for treating nutrient solution spent from an experimental closed-loop nursery was evaluated by means of a combination of culture-dependent and independent molecular techniques. A dense inoculum of the fungal plant pathogen Fusarium oxysporum f.sp. lycopersici was applied in the fertigation system (106 cells per mL). Indigenous and introduced populations of eubacteria and fungi were assessed in the nutrient solution, the HSSF influent/effluent, and a sand bed transect by isolation on selective media, as well as by quantitative qPCR and next-generation sequencing (NGS) on target ribosomal genes. The HSSF effectively reduced viable Fusarium propagules and fungal gene content with an efficiency consistently above 99.9% (5 orders of magnitude down). On the other hand, Fusarium cells accumulated in the sand bed, indicating that physical entrapment was the main removal mechanism. The viability of retained Fusarium cells tended to decrease in time, so that treatment efficiency might be enhanced by antagonistic species from the genera Bacillus, Pseudomonas, and Trichoderma, also identified in the sand bed. Indigenous bacterial populations from the HSSF effluent were reduced by 87.2% and 99.9% in terms of colony forming units and gene counts, respectively, when compared to the influent. Furthermore, microbial populations from the HSSF effluent were different from those observed in the sand bed and the influent. In summary, the HSSF microbial disinfestation efficiency is comparable to that reported for other more intensive and costly methodologies, while allowing a significant recovery of water and nutrients.

Antimicrobial, herbicidal and antifeedant activities of mansonone E from the heartwoods of Mansonia gagei Drumm.

In vitro biological activities including anti-phytopathogenic fungi, antibacterial, antifeedant and herbicidal activities of the extracts from the heartwoods of Mansonia gagei Drumm. were evaluated. The dichloromethane (DCM) extract displayed antifungal activity against four plant pathogenic fungi (Alternaria porri, Colletotrichum gloeosporioides, Fusarium oxysporum and Phytophthora parasitica) higher than the methanolic (MeOH) extract. The separation of the DCM extract using bioassay guided antifungal activity against P. parasitica led to the isolation of mansorins A, B, and C, mansonones C, E, G and H. Among isolated compounds, mansonone E displayed the highest antifungal activity against P. parasitica, followed by mansonone C, mansorin B and mansonone G. This potent compound revealed the same minimum inhibitory concentrations (MIC) of 31 μg mL−1 against C. gloeosporioides and P. parasitica, and minimum fungicidal concentration (MFC) of 31 and 125 μg mL−1, respectively. Moreover, mansonone E exhibited highly significant antibacterial activity against both Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc) with MIC and minimum bactericidal concentration (MBC) as 7.8 and >500 μg mL−1, respectively. This compound furthermore could inhibit the feed of Spodoptera litura with 45.9% antifeedant and significantly herbicidal activity reduced the shoot and root growth of Brassica chinensis, Oryza sativa, Mimosa pigra and Echinochlooa crus-galli. Mansonone E has potential as a new natural pesticide for agricultural plant pathogen management.

FUNGICIDAL POTENTIAL OF ALLELOPATHIC WEED Cenchrus pennisetiformis ON GROWTH OF Fusarium oxysporum f. sp. lycopersici UNDER CHROMIUM STRESS

ABSTRACT The present study was conducted to assess antifungal potential of the allelopathic grass Cenchrus pennisetiformis Hochst. & Steud. against the fungal plant pathogen Fusarium oxysporum f. sp. lycopersici (cause of tomato wilt disease) under chromium stress. Laboratory experiments were performed in 10 mL volume glass test tubes each containing 1.0 mL of malt extract broth with seven concentrations (0, 50, 100, 150, 200, 250, 300 and 350 ppm) of each of Cr(III) and Cr(VI), and two concentrations (5% and 6%) of methanolic leaf, stem or root extract of C. pennisetiformis. A metal + weed extract amended medium was inoculated with the pathogen and incubated for 7 days at 25 C. Different concentrations of Cr(III) and Cr(VI) proved equally inhibitory resulting in 10-84% and 18-89% reduction in fungal biomass, respectively. Methanolic leaf, stem and root extracts of the weed reduced fungal biomass by 12-25%, 14-23% and 46-50%, respectively, over negative control. In combined application of methanolic extracts of different parts of C. pennisetiformis and metal solutions, root extract in combination with either Cr(III) or Cr(VI) showed the highest inhibitory potential against the fungus followed by leaf and stem extracts. In combination with methanolic root, leaf and stem extracts, different concentrations of Cr(III) and Cr(VI) significantly reduced fungal biomass by 54-99%, 14-99% and 9-95%, respectively, over negative control. Such studies have not been carried out previously. Results of the present investigation suggest that F. oxysporum oxysporum f. sp. lycopersici, the cause of Fusarium wilt disease in tomato, can be managed by application of extracts (or alternatively biomass) of C. pennisetiformis in chromium contaminated soils.

Fungal pathogenesis: Host modulation every which way.

The plant pathogenic fungus Fusarium oxysporum secretes an effector that is similar to a plant peptide hormone, underscoring the variety of mechanisms that plant pathogens have evolved to tamper with host physiology.

Synthesis and characterization of silver nanoparticles and their antimicrobial efficacy

ABSTRACTAn efficient protocol for synthesis of silver nanoparticles (AgNPs) using the combination of aqueous extract of Tinospora cordifolia leaves and 5 mM silver nitrate (AgNO3) solution was developed. This study revealed that bioactive compounds present in the extract function as stabilizing and capping agent for AgNPs. Scanning electron microscope and transmission electron microscope studies confirm the structure and surface morphology of the AgNPs. The size of synthesized AgNPs was in the range of 30–50 nm having spherical morphology. The crystalline nature of NPs was defined by the X-ray diffraction pattern. The AgNPs were found to be toxic against pathogenic bacteria such as Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), and Staphylococcus aureus (ATCC 29213) and against plant pathogenic fungi Fusarium oxysporum (MTCC 8608) and Sclerotinia sclerotiorum (MTCC 8785). The use of AgNPs as antibacterial and antifungal agent is advantageous over other methods for control of pathogenic microorganisms, and it can be of great importance in developing novel drugs for curing many lethal diseases.

Studies on antagonistic effect against plant pathogenic fungi from Endophytic fungi isolated from Hottuynia Cordata Thunb and screening for Siderophore and indole-3-acetic acid production

The endophytic fungi that colonizes internal plant tissues without causing apparent harm to their host were isolated from healthy leaf, root and stem of Hottuynia cordata Thunb. Twelve fungal isolates found were identified by their morphological characteristic and using molecular technique. The result showed that ten isolates belonging to Ascomycota were presumed to be in genus Colletotrichum, Lasiodiplodia and Fusarium in eight isolates and two isolates were identified to class Dothideomycetes and Sordariomycetes. Two unidentified isolates (R14 and R15), confined only to root segments were isolated, these members may be from the group of Mycelia-Sterilia. The evaluation of antagonistic activity of twelve fungal endophytes isolated from healthy Houttuynia cordata Thumb against Trichoderma harzianum and five plant pathogenic fungi (Fusarium oxysporum, Sclerotium rolfsii, Rhizoctonia sp., Alternaria brassicicola and Phytophthora palmivora) by dual culture technique were performed. The in vitro antagonistic activities as two types of activities in this study; mycoparasitism and competition were found. Endophyte isolate B06, B12, B09 and R15 gave the highest percent inhibition of radial growth against to the plant pathogenic fungi (F. oxysporum, S. rolfsii, A. brassicicola) and T. harzianum within 24.22%, 29.07%, 13.54 and 24.15%, respectively. Endophyte isolate R14 showed the highest antagonistic activity to Rhizoctonia sp. and P. palmivora with 39.33% and 33.34% respectively. For the siderophore production, the seven active endophyte isolates showed orange halo formed around the colonies more than 30 mm on CAS agar. Three endophyte isolates efficiently produced IAA more than 24 µg/ml. The active endophyte isolates B06 identified as Lasiodiplodia pseudotheobromae showed the highest ability to produce IAA (37.034 µg/ml) and also showed the highest orange halo formed around the colonies which determined to siderophore production.

PFungiway: a series of plasmid vectors used for gene manipulation in fungi

A series of plasmid vectors, named pFungiway, was constructed for the purpose of simple and versatile gene manipulation in a wide range of fungi. The backbone of these vectors consists of the binary plasmid pCAMBIA2200, which can be introduced into fungal cells by Agrobacterium tumefaciens-mediated transformation. Objective genes can be easily inserted into the vector by the use of Gateway technology, without relying on any restriction cleavage sites. The pFungiway vectors are composed of two types: expression vectors, in which the expression of the objective genes is driven by a constitutive promoter; and repression vectors, in which the expression of the endogenous target gene is repressed by RNA interference. Either of two genes conferring resistance to hygromycin B or G418 can be used as a selective marker. The availability of pFungiway vectors was confirmed by the use of fluorescent reporter genes in the basidiomycete Flammulina velutipes and in the plant pathogenic fungus Fusarium oxysporum.

MYCOLYTIC ACTIVITY OF PHOSPHATE MOBILIZING SOILBA CTERIA OF GENUS BACILLUS COHN

The aim of this research was study of the chitinolytic activity of phosphateobilizing soil bacteria of genus Bacillus and their antagonistic properties towards microscopic fungi. Methods. In this research 16 strains of phosphate-mobilizing soil bacteria of genus Bacillus and saprophytic and plant pathogenic strains of micrtomycetes were investigated. The antagonistic activity of bacilli against micromycetes was determined by the method of blocks and holes. Bacilli on agar medium and also their supernatants were used. Inhibition of fungal growth under co-cultivation with bacilli under static conditions in the liquid culture medium was determined gravimetrically by the difference of dry weight mycelium in control and in experiment. Bacilli chitinolytic activity was determined photocolorimetrically by the formation of reducing sugars by hydrolysis of colloidal chitin using 3,5-dinitrosalicylic acid. Student test for 5% significance level was used for statistical processing of the obtained data. Results. The presence of chitinolytic activity in all tested bacilli in colloidal chitin medium was established. B. megaterium 16, B. pumilus 7, B. cereus v mycoides 10 strains showed high chitinolytic activity, they were also characterized by high antagonistic activity against plant pathogenic fungi (Fusarium oxysporum 54 and Trichothecium roseum 658). Bacilli were capable to using autoclaved mycelium as the sole of carbon and nitrogen source. Cultivation of bacteria and microscopic fungi under static conditions showed growth inhibition and changes in morphological features – blistering and areas of lysis of mycelium. Conclusions. It was established that phosphate-mobilizing strains of soil bacteria of the genus Bacillus showed chitinolytic activity and growth inhibition of plant pathogens and caused their morphological changes in co-culture. The direct relationship between the antagonistic and chitinolytic activity of bacilli was demonstrated. The bacilli ability to use autoclaved fungal mycelium as a sole source of carbon and nitrogen was showed on the example of B. cereus v. mycoides 10.

The F-box protein Fbp1 functions in the invasive growth and cell wall integrity mitogen-activated protein kinase (MAPK) pathways in Fusarium oxysporum.

F-box proteins determine substrate specificity of the ubiquitin-proteasome system. Previous work has demonstrated that the F-box protein Fbp1, a component of the SCF(Fbp1) E3 ligase complex, is essential for invasive growth and virulence of the fungal plant pathogen Fusarium oxysporum. Here, we show that, in addition to invasive growth, Fbp1 also contributes to vegetative hyphal fusion and fungal adhesion to tomato roots. All of these functions have been shown previously to require the mitogen-activated protein kinase (MAPK) Fmk1. We found that Fbp1 is required for full phosphorylation of Fmk1, indicating that Fbp1 regulates virulence and invasive growth via the Fmk1 pathway. Moreover, the Δfbp1 mutant is hypersensitive to sodium dodecylsulfate (SDS) and calcofluor white (CFW) and shows reduced phosphorylation levels of the cell wall integrity MAPK Mpk1 after SDS treatment. Collectively, these results suggest that Fbp1 contributes to both the invasive growth and cell wall integrity MAPK pathways of F. oxysporum.

INVESTIGATION OF ANTIMICROBIAL PROPERTIES OF SILVER NANOPARTICLES STABILIZED BY MALEIC ACID COPOLYMERS

Silver nanoparticles have been prepared by the reduction of the corresponding metal salt with NaBH 4 in the presence of appropriate dispersing agents, namely, copolymers of maleic acid with N-vinylpyrrolidone, ethylene and styrene or their amphyphi- lic derivative containing octadecylamide ligands. The silver colloids identified by optical absorption spectroscopy were synthesized when the copolymer concentrations were lower than their critical aggregation concentrations and copolymer/Ag+ molar ratio no greater than a unit. According to the data of transmission electron microscopy, the obtained Ag nanoparticles were spherical-shaped particles 1—2 nm in size. Colloidal solutions of the prepared nanosilver showed a strong inhibiting antifungal activity against a fungal plant pathogen Fusarium oxysporum and also Gram-negative, Gram-positive bacteria and yeast. The silver nanoparticles stabilized with more hydrophilic compounds from among the investigated copolymers demonstrated the higher antibacterial and antifungal activity.

Heterologous expression of the antifungal β-chitin binding protein CBP24 from bacillus thuringiensis and its synergistic action with bacterial chitinases.

The genome sequence analysis of Bacillus thuringiensis serovar konkukian S4 has shown to contain two chitinases (Chi74, Chi39) and two chitin-binding proteins (CBP50 and CBP24). The Chi74, Chi39 and CBP50 have been characterized previously. The chitin-binding protein CBP24 was cloned and heterologously expressed in Escherichia coli. The recombinant protein was purified using a Ni-NTA purification system. The purified protein was used to study its substrate binding activity using crystalline chitin variants as substrates. The Bmax and Kd values have shown that it preferably binds to β-type of the crystalline chitin at a range of pH with peak activity between 5.5-7.5. To elucidate the role of CBP24 in the chitin degradation system of S4, the purified chitinases Chi74, Chi39 along with the ChiA from Serratia proteamcualans were used in different combinations with the CBP24 and chitinolytic activity was assayed. It was shown that the CBP24 acts synergistically with chitin degradation activity of bacterial chitinases non-specifically. Moreover, the CBP24 has shown antifungal activity against plant pathogenic fungi Fusarium oxysporum and Rhizoctonia solani. The present study will lead us to develop a technology for environmental friendly conversion of chitin to valuable products.

Naturally produced citral can significantly inhibit normal physiology and induce cytotoxicity on Magnaporthe grisea

Given the importance of finding alternatives to synthetic fungicides, the antifungal effects of natural product citral on six plant pathogenic fungi (Magnaporthe grisea, Gibberella zeae, Fusarium oxysporum, Valsa mali, Botrytis cinerea, and Rhizoctonia solani) were determined. Mycelial growth rate results showed that citral possessed high antifungal activities on those test fungi with EC50 values ranging from 39.52 to 193.00 µg/mL, which had the highest inhibition rates against M. grisea. Further action mechanism of citral on M. grisea was carried out. Citral treatment was found to alter the morphology of M. grisea hyphae by causing a loss of cytoplasm and distortion of mycelia. Moreover, citral was able to induce an increase in chitinase activity in M. grisea, indicating disruption of the cell wall. These results indicate that citral may act by disrupting cell wall integrity and membrane permeability, thus resulting in physiology changes and causing cytotoxicity. Importantly, the inhibitory effect of citral on M. grisea appears to be associated with its effects on mycelia reducing sugar, soluble protein, chitinase activity, pyruvate content, and malondialdehyde content.

Molecular inversion probe: a new tool for highly specific detection of plant pathogens.

Highly specific detection methods, capable of reliably identifying plant pathogens are crucial in plant disease management strategies to reduce losses in agriculture by preventing the spread of diseases. We describe a novel molecular inversion probe (MIP) assay that can be potentially developed into a robust multiplex platform to detect and identify plant pathogens. A MIP has been designed for the plant pathogenic fungus Fusarium oxysporum f.sp. conglutinans and the proof of concept for the efficiency of this technology is provided. We demonstrate that this methodology can detect as little as 2.5 ng of pathogen DNA and is highly specific, being able to accurately differentiate Fusarium oxysporum f.sp. conglutinans from other fungal pathogens such as Botrytis cinerea and even pathogens of the same species such as Fusarium oxysporum f.sp. lycopersici. The MIP assay was able to detect the presence of the pathogen in infected Arabidopsis thaliana plants as soon as the tissues contained minimal amounts of pathogen. MIP methods are intrinsically highly multiplexable and future development of specific MIPs could lead to the establishment of a diagnostic method that could potentially screen infected plants for hundreds of pathogens in a single assay.

Plant methyl salicylate induces defense responses in the rhizobacterium Bacillus subtilis.

Bacillus subtilis is a rhizobacterium that promotes plant growth and health. Cultivation of B. subtilis with an uprooted weed on solid medium produced pleat-like architectures on colonies near the plant. To test whether plants emit signals that affect B. subtilis colony morphology, we examined the effect of plant-related compounds on colony morphology. Bacillus subtilis formed mucoid colonies specifically in response to methyl salicylate, which is a plant-defense signal released in response to pathogen infection. Methyl salicylate induced mucoid colony formation by stimulating poly-γ-glutamic acid biosynthesis, which formed enclosing capsules that protected the cells from exposure to antimicrobial compounds. Poly-γ-glutamic acid synthesis depended on the DegS-DegU two-component regulatory system, which activated DegSU-dependent gene transcription in response to methyl salicylate. Bacillus subtilis did not induce plant methyl salicylate production, indicating that the most probable source of methyl salicylate in the rhizosphere is pathogen-infected plants. Methyl salicylate induced B. subtilis biosynthesis of the antibiotics bacilysin and fengycin, the latter of which exhibited inhibitory activity against the plant pathogenic fungus Fusarium oxysporum. We propose that B. subtilis may sense plants under pathogen attack via methyl salicylate, and express defense responses that protect both B. subtilis and host plants in the rhizosphere.

Tandem combination of Trigonella foenum-graecum defensin (Tfgd2) and Raphanus sativus antifungal protein (RsAFP2) generates a more potent antifungal protein

Plant defensins are small (45 to 54 amino acids) positively charged antimicrobial peptides produced by the plant species, which can inhibit the growth of a broad range of fungi at micro-molar concentrations. These basic peptides share a common characteristic three-dimensional folding pattern with one α-helix and three β-sheets that are stabilized by eight disulfide-linked cysteine residues. Instead of using two single-gene constructs, it is beneficial when two effective genes are made into a single fusion gene with one promoter and terminator. In this approach, we have linked two plant defensins namely Trigonella foenum-graecum defensin 2 (Tfgd2) and Raphanus sativus antifungal protein 2 (RsAFP2) genes by a linker peptide sequence (occurring in the seeds of Impatiens balsamina) and made into a single-fusion gene construct. We used pET-32a+ vector system to express Tfgd2-RsAFP2 fusion gene with hexahistidine tag in Escherichia coli BL21 (DE3) pLysS cells. Induction of these cells with 1 mM IPTG achieved expression of the fusion protein. The solubilized His6-tagged recombinant fusion protein was purified by immobilized-metal (Ni2+) affinity column chromatography. The final yield of the fusion protein was 500 ng/μL. This method produced biologically active recombinant His6-tagged fusion protein, which exhibited potent antifungal action towards the plant pathogenic fungi (Botrytis cinerea, Fusarium moniliforme, Fusarium oxysporum, Phaeoisariopsis personata and Rhizoctonia solani along with an oomycete pathogen Phytophthora parasitica var nicotianae) at lower concentrations under in vitro conditions. This strategy of combining activity of two defensin genes into a single-fusion gene will definitely be a promising utility for biotechnological applications.

Molecular characterization of fungal endophytes from Calotropis procera plants in Taif region (Saudi Arabia) and their antifungal activities

Fungal endophytes were isolated from the leaves of Calotropis procera (Apocynaceae) collected from Taif region (Saudi Arabia). Thirty-three different taxa were recovered. The overall foliar colonization rate was 35.1%. A total of 161 isolates were obtained and identified into 33 distinct operational taxonomic units based on the sequencing of the internal transcribed spacer regions of the rRNA gene. The most prevalent fungi were Aspergillus flavus, Chaetomium globosum, Cochliobolus lunatus, Fusarium dimerum, F. oxysporum, and Penicillium chrysogenum. A total of 161 isolates were tested for antifungal activities against four plant pathogenic fungi (Alternaria alternata, Fusarium oxysporum, Botrytis cinerea, and Pythium ultimum), of which 33 isolates showed antifungal activity against at least one plant pathogenic fungi. Four isolates of Chaetomium globosum and three isolates of Myrothecium verrucaria showed the strongest antifungal activity. This study reported the occurrence of a much wider spectrum of fungi, when compared with previous work. Also, it confirmed the variation of different isolates from the same species in terms of antifungal activity.

Analysis of hairpin RNA transgene-induced gene silencing in Fusarium oxysporum.

BackgroundHairpin RNA (hpRNA) transgenes can be effective at inducing RNA silencing and have been exploited as a powerful tool for gene function analysis in many organisms. However, in fungi, expression of hairpin RNA transcripts can induce post-transcriptional gene silencing, but in some species can also lead to transcriptional gene silencing, suggesting a more complex interplay of the two pathways at least in some fungi. Because many fungal species are important pathogens, RNA silencing is a powerful technique to understand gene function, particularly when gene knockouts are difficult to obtain. We investigated whether the plant pathogenic fungus Fusarium oxysporum possesses a functional gene silencing machinery and whether hairpin RNA transcripts can be employed to effectively induce gene silencing.ResultsHere we show that, in the phytopathogenic fungus F. oxysporum, hpRNA transgenes targeting either a β-glucuronidase (Gus) reporter transgene (hpGus) or the endogenous gene Frp1 (hpFrp) did not induce significant silencing of the target genes. Expression analysis suggested that the hpRNA transgenes are prone to transcriptional inactivation, resulting in low levels of hpRNA and siRNA production. However, the hpGus RNA can be efficiently transcribed by promoters acquired either by recombination with a pre-existing, actively transcribed Gus transgene or by fortuitous integration near an endogenous gene promoter allowing siRNA production. These siRNAs effectively induced silencing of a target Gus transgene, which in turn appeared to also induce secondary siRNA production. Furthermore, our results suggested that hpRNA transcripts without poly(A) tails are efficiently processed into siRNAs to induce gene silencing. A convergent promoter transgene, designed to express poly(A)-minus sense and antisense Gus RNAs, without an inverted-repeat DNA structure, induced consistent Gus silencing in F. oxysporum.ConclusionsThese results indicate that F. oxysporum possesses functional RNA silencing machineries for siRNA production and target mRNA cleavage, but hpRNA transgenes may induce transcriptional self-silencing due to its inverted-repeat structure. Our results suggest that F. oxysporum possesses a similar gene silencing pathway to other fungi like fission yeast, and indicate a need for developing more effective RNA silencing technology for gene function studies in this fungal pathogen.