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1.
Field manipulations were used to determine the importance of two predatory polychaetes, Nereis virens Sars and Glycera dibranchiata Ehlers, and epibenthic predators in structuring an intertidal soft-bottom community in Maine. Epibenthic predators were excluded from portions of the soft bottom using cages which also enclosed elevated densities of the predatory polychaetes. The experiments ran 10 wk and 20 wk beginning in June 1979. Exclusion of epibenthic predators had no effect on infaunal densities after 10 wk but produced ≈ 1.5-fold increase in total density after 20 wk. Since gulls (Larus spp.) avoided all cages, including those not designed to exclude epibenthic predators, the effect of gull predation on infaunal abundances was not tested using exclusion cages. Crabs, Carcinus maenas (Linnaeus) and Cancer irroratus Say were observed in cages not designed to exclude predators.Densities of Nephtys incisa Malmgren, Polydora ligni Webster, Streblospio benedicti Webster, Scoloplos robustus Verrill, phyllodocids, and bivalves were highest in cages containing elevated Glycera dibranchiata density and lowest in cages containing elevated Nereis virens density. N. virens was the only taxon whose abundance was reduced in the presence of Glycera dibranchiata which may account for high infaunal densities in the G. dibranchiata treatment. Laboratory experiments demonstrated that G. dibranchiata are capable of preying on Nereis virens. Additional field experiments revealed that the presence of N. Virens reduced the abundance of some taxa within the first 10 days of colonization. N. virens may have reduced infaunal densities by predation and/or disturbance at the sediment surface. These results suggest that complex interactions within the infauna are important in structuring marine soft-bottom communities.  相似文献   

2.
To screen biocontrol agents against Burkholderia plantarii, the causative agent of rice seedling blight, we employed catechol, an analog of the virulence factor tropolone, to obtain chemical stress-resistant microorganisms. The fungal isolate PS1-7, identified as a strain of Trichoderma virens, showed the highest resistance to catechol (20 mM) and exhibited efficacy as a biocontrol agent for rice seedling blight. During investigation of metabolic traits of T. virens PS1-7 exposed to catechol, we found a secondary metabolite that was released extracellularly and uniquely accumulated in the culture. The compound induced by chemical stress due to catechol was subsequently isolated and identified as a sesquiterpene diol, carot-4-en-9,10-diol, based on spectroscopic analyses. T. virens PS1-7 produced carot-4-en-9,10-diol as a metabolic response to tropolone at concentrations from 0.05 to 0.2 mM, and the response was enhanced in a dose-dependent manner, similar to its response to catechol at concentrations from 0.1 to 1 mM. Some iron chelators, such as pyrogallol, gallic acid, salicylic acid, and citric acid, at 0.5 mM also showed activation of T. virens PS1-7 production of carot-4-en-9,10-diol. This sesquiterpene diol, formed in response to chemical stress, promoted conidiation of T. virens PS1-7, suggesting that it is involved in an autoregulatory signaling system. In a bioassay of the metabolic and morphological responses of T. virens PS1-7, conidiation in hyphae grown on potato dextrose agar (PDA) plates was either promoted or induced by carot-4-en-9,10-diol. Carot-4-en-9,10-diol can thus be regarded as an autoregulatory signal in T. virens, and our findings demonstrate that intrinsic intracellular signaling regulates conidiation of T. virens.  相似文献   

3.
Lichens are considered freezing tolerant, although few species have been tested. Growth, a robust measure of fitness integrating processes in all partners of a lichen thallus, has not yet been used as a viability measure after freezing. We compared relative growth rates (RGR) after freezing with short-term viability measures of photo- and mycobiont functions in the coastal Lobaria virens and the widespread L. pulmonaria to test the hypothesis that low temperature shapes the coastal distribution of L. virens. Hydrated thalli from sympatric populations were subjected to freezing at −10, −20 and −40 °C for 5 h. The rate of cooling and subsequent warming was 5 °C h−1. Short-term viability measures of photobiont (maximal photosystem II efficiency, effective PSII yield) and mycobiont viability (conductivity index), as well as subsequent RGR, were assessed. The exotherms showed that L. virens froze at −3 °C; L. pulmonaria, at −4 °C. Freezing significantly impaired short-term viability measures of both photo- and mycobiont, particularly in the coastal species. Lobaria pulmonaria grew 2.1 times faster than L. virens, but the short-term damage after one freezing event did not affect the long-term RGR in any species. Thereby, short-term responses were impaired by freezing, long-term responses were not. While the lacking RGR-responses to freezing suggest that freezing tolerance does not shape the coastal distribution of L. virens, the significant reported adverse short-term effects in L. virens may be aggravated by repeated freezing-thawing cycles in cold winters. In such a perspective, repeated freezing may eventually lead to reduced long-term fitness in L. virens.  相似文献   

4.

Aims

This work was conducted to examine the effects of volatile organic compounds (VOCs) from Trichoderma virens and the 4-phosphopantetheinyl transferase 1 (TvPPT1) mutant in growth promotion and induction of defense responses of Arabidopsis thaliana seedlings using a co-cultivation system in vitro.

Methods

The contribution of VOCs to plant development and immunity was assessed by comparing the effectiveness of WT and Δppt1 mutant strains of T. virens in the formation of lateral roots and protection conferred against Botrytis cinerea. VOCs released by T. virens and Δppt1 mutant were compared by gas chromatography–mass spectrometry.

Results

Plants exposed to volatiles from WT T. virens showed 2-fold increase in fresh weight when compared to axenically-grown seedlings, which correlated with increased root branching and enhanced expression of the jasmonic acid-responsive marker pLox2:uidA as well as accumulation of jasmonic acid and hydrogen peroxide. T. virens produced a series of hydrocarbon terpenes, including the sesquiterpenes β-caryophyllene, (?)-β-elemene, germacrene D, τ-cadinene, δ-cadinene, α-amorphene, and τ-selinene and the monoterpenes β-myrcene, trans-β-ocimene, and cis-β-ocimene that were absent in TvPPT1 mutant.

Conclusions

Our results indicate that T. virens VOCs elicit both development and defense programs and that PPT1 plays an important role in biosynthesis of terpenes and plant protection against B. cinerea.  相似文献   

5.
Peptide Synthetase Gene in Trichoderma virens   总被引:1,自引:0,他引:1       下载免费PDF全文
Trichoderma virens (synonym, Gliocladium virens), a deuteromycete fungus, suppresses soilborne plant diseases caused by a number of fungi and is used as a biocontrol agent. Several traits that may contribute to the antagonistic interactions of T. virens with disease-causing fungi involve the production of peptide metabolites (e.g., the antibiotic gliotoxin and siderophores used for iron acquisition). We cloned a 5,056-bp partial cDNA encoding a putative peptide synthetase (Psy1) from T. virens using conserved motifs found within the adenylate domain of peptide synthetases. Sequence similarities with conserved motifs of the adenylation domain, acyl transfer, and two condensation domains support identification of the Psy1 gene as a gene that encodes a peptide synthetase. Disruption of the native Psy1 gene through gene replacement was used to identify the function of this gene. Psy1 disruptants produced normal amounts of gliotoxin but grew poorly under low-iron conditions, suggesting that Psy1 plays a role in siderophore production. Psy1 disruptants cannot produce the major T. virens siderophore dimerum acid, a dipetide of acylated Nδ-hydroxyornithine. Biocontrol activity against damping-off diseases caused by Pythium ultimum and Rhizoctonia solani was not reduced by the Psy1 disruption, suggesting that iron competition through dimerum acid production does not contribute significantly to disease suppression activity under the conditions used.  相似文献   

6.
Ganoderma boninense is the causal agent of a devastating disease affecting oil palm in Southeast Asian countries. Basal stem rot (BSR) disease slowly rots the base of palms, which radically reduces productive lifespan of this lucrative crop. Previous reports have indicated the successful use of Trichoderma as biological control agent (BCA) against G. boninense and isolate T. virens 7b was selected based on its initial screening. This study attempts to decipher the mechanisms responsible for the inhibition of G. boninense by identifying and characterizing the chemical compounds as well as the physical mechanisms by T. virens 7b. Hexane extract of the isolate gave 62.60% ± 6.41 inhibition against G. boninense and observation under scanning electron microscope (SEM) detected severe mycelial deformation of the pathogen at the region of inhibition. Similar mycelia deformation of G. boninense was observed with a fungicide treatment, Benlate® indicating comparable fungicidal effect by T. virens 7b. Fraction 4 and 5 of hexane active fractions through preparative thin layer chromatography (P-TLC) was identified giving the best inhibition of the pathogen. These fractions comprised of ketones, alcohols, aldehydes, lactones, sesquiterpenes, monoterpenes, sulphides, and free fatty acids profiled through gas chromatography mass spectrometry detector (GC/MSD). A novel antifungal compound discovery of phenylethyl alcohol (PEA) by T. virens 7b is reported through this study. T. virens 7b also proved to be an active siderophore producer through chrome azurol S (CAS) agar assay. The study demonstrated the possible mechanisms involved and responsible in the successful inhibition of G. boninense.  相似文献   

7.
Trichoderma spp. are cosmopolitan soil fungi that are highly resistant to many toxic compounds. Here, we show that Trichoderma virens and T. reesei are tolerant to aromatic amines (AA), a major class of pollutants including the highly toxic pesticide residue 3,4-dichloroaniline (3,4-DCA). In a previous study, we provided proof-of-concept remediation experiments in which another soil fungus, Podospora anserina, detoxifies 3,4-DCA through its arylamine N-acetyltransferase (NAT), a xenobiotic-metabolizing enzyme that enables acetyl coenzyme A-dependent detoxification of AA. To assess whether the N-acetylation pathway enables AA tolerance in Trichoderma spp., we cloned and characterized NATs from T. virens and T. reesei. We characterized recombinant enzymes by determining their catalytic efficiencies toward several toxic AA. Through a complementary approach, we also demonstrate that both Trichoderma species efficiently metabolize 3,4-DCA. Finally, we provide evidence that NAT-independent transformation is solely (in T. virens) or mainly (in T. reesei) responsible for the observed removal of 3,4-DCA. We conclude that T. virens and, to a lesser extent, T. reesei likely utilize another, unidentified, metabolic pathway for the detoxification of AA aside from acetylation. This is the first molecular and functional characterization of AA biotransformation in Trichoderma spp. Given the potential of Trichoderma for cleanup of contaminated soils, these results reveal new possibilities in the fungal remediation of AA-contaminated soil.  相似文献   

8.
9.
Gliocladium virens is a common saprophytic fungus that is mycoparasitic on a large number of fungi. Responses of G. virens toward its environment were examined by monitoring the presence of extracellular proteins in culture fluid during time course experiments. Culture fluid of G. virens grown on glucose, washed cell walls of Rhizoctonia solani (one of its hosts), olive oil, or chitin contained β-glucanase, N-acetylglucosaminidase, lipase, and proteinase activities. There were relatively minor amounts of other enzymatic activities tested. Levels of extracellular enzyme activity varied with the age of the culture and the substrate used as the carbon source. Substrate-associated differences in enzyme activities were detected as early as 8 h after transfer of mycelia from stationary-phase cultures to fresh media. When G. virens was grown on host cell wall material, β-glucanase had the greatest specific activity of any enzyme tested at 8 h. This result suggests that β-glucanase may be the first enzyme important in the G. virens-R. solani interaction. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that some of the polypeptides were present in the culture fluid at relatively constant amounts and others accumulated early, at intermediate times, or late in the 8-day incubation test period. Several of the polypeptides present in the culture fluid during the first 24 h disappeared completely by 48 h. Consequently, it appears that extracellular proteins in cultures of G. virens are regulated by a combination of gene regulation and protein degradation.  相似文献   

10.
The effects of the interaction between Suillus luteus (L.) Roussel and Trichoderma virens (J.H. Mill., Giddens & A.A. Foster) Arx on Pinus sylvestris var. mongolica Litv. were studied using plant physiology, mycorrhizal science, forest pathology, and biochemistry. Seedling growth and physiological parameters were determined, including the colonization rate of mycorrhizal fungi, biomass, root activity, photosynthetic pigment content, soluble protein content, antioxidant enzyme activities, rhizosphere soil enzyme activities, and protective enzyme activities. In addition, an optimal resistance system involving T. virens, mycorrhizal fungus (S. luteus), and P. sylvestris var. mongolica seedlings was constructed. Synergies between S. luteus and T. virens were observed, and most of the parameters of P. sylvestris var. mongolica seedlings inoculated with S. luteus 30 days + T. virens were higher than other treatments. After three months, when compared the control, the S. luteus 30 days + T. virens treatment gave increases in height (42.3 %); collar diameter (66.7 %); fresh weight (54 %); dry weight (50 %); soluble protein content (69.86 %); root activity (150 %); chlorophyll a (77.6 %); chlorophyll b (70.5 %); carotenoids (144 %); CAT activity (876.9 %); POD activity (268.3 %); SOD activity (66.18 %); β-1,3-glucanase activity (125.8 %); chitinase activity (40 %); rhizosphere soil catalase activity (97.8 %); and phosphatase activity (266.7 %). These results indicate that there may be a stimulating factor between S. luteus and T. virens when they are inoculated together (S. luteus 30 days + T. virens).  相似文献   

11.
Effect of salinity on fertilization and early development of the polychaeta Nereis virens (Sars) from the White Sea was examined in laboratory experiments. The comparison of salinity resistance of different developmental stages of N. virens showed gradual increase of euryhalinity during ontogenesis—from fertilized eggs to juveniles.Successful fertilization and effective development (≥70-75%) was possible in narrow salinity range 22-34‰. The salinity range of successful development for trochophore and nectochaete larvae reached 14-45‰. This increase of the limits of salinity tolerance in trochophore and nectochaete larvae probably was due to the formation of protonephridium system.Rate of metamorphosis of N. virens was tested under temperature 5, 10, 17 and 23 °C and salinity 22-14‰. The highest rate of metamorphosis was marked at the temperature of 23 °C in salinities higher than 14‰.Our data confirms that N. virens originates from warm seas with oceanic salinity.  相似文献   

12.
13.
Filamentous fungi belonging to the genus Trichoderma have long been recognized as agents for the biocontrol of plant diseases. In this work, we investigated the mechanisms involved in the defense responses of Arabidopsis thaliana seedlings elicited by co-culture with Trichoderma virens and Trichoderma atroviride. Interaction of plant roots with fungal mycelium induced growth and defense responses, indicating that both processes are not inherently antagonist. Expression studies of the pathogenesis-related reporter markers pPr1a:uidA and pLox2:uidA in response to T. virens or T. atroviride provided evidence that the defense signaling pathway activated by these fungi involves salicylic acid (SA) and/or jasmonic acid (JA) depending on the amount of conidia inoculated. Moreover, we found that Arabidopsis seedlings colonized by Trichoderma accumulated hydrogen peroxide and camalexin in leaves. When grown under axenic conditions, T. virens produced indole-3-carboxaldehyde (ICAld) a tryptophan-derived compound with activity in plant development. In Arabidopsis seedlings whose roots are in contact with T. virens or T. atroviride, and challenged with Botrytis cinerea in leaves, disease severity was significantly reduced compared with axenically grown seedlings. Our results indicate that the defense responses elicited by Trichoderma in Arabidopsis are complex and involve the canonical defense hormones SA and JA as well as camalexin, which may be important factors in boosting plant immunity.Key words: Arabidopsis, Trichoderma, phytostimulation, defense responses, jasmonic acid, salicylic acid, camalexin  相似文献   

14.
It is crucial to study how food resources are allocated in order to understand how invertebrate species of soft-bottomed benthic communities can live in the same environment, especially when belonging to the same trophic level. On the southern shore of the Lower St. Lawrence Estuary, the polychaetes Nereis virens (Nereidae) and Nephtys caeca (Nephtyidae) represent the main infaunal predators and are known to regulate (by predation) other populations within their community. For these animal populations, there is a high degree of spatial overlap in the horizontal dimension as well as vertically in the sediment column. The purpose of this study was to describe and compare the feeding activity of N. virens and N. caeca in relation to several environmental factors. The feeding activity of N. caeca was further studied under natural and experimental conditions and a feeding experiment was carried out to evaluate how the food resource is subdivided in conditions of high spatial overlap. Finally, the prospecting activity of N. virens was described under natural conditions. N. virens and N. caeca exhibited a high degree of dietary overlap, particularly at the adult stage. This food resource overlap can easily influence the regulation of these species, even though they display different feeding responses to environmental stimuli. Tides and storm events can also influence the feeding behaviour. We conclude that different behavioural feeding responses likely favour the occurrence of these two species in the same trophic environment.  相似文献   

15.
Different solid state fermentation (SSF) sources were tested such as cantaloupe and watermelon rinds, orange and banana peels, for the production of polygalacturonase (PG) and xylanase (Xyl) by Trichoderma harzianum and Trichoderma virens. The maximum production of both PG and Xyl were obtained by T. harzianum and T. virnes grown on cantaloupe and watermelon rinds, respectively. Time course, moisture content, temperature, pH, supplementation with carbon and nitrogen sources were optimized to achieve the maximum production of both PG and Xyl of T. harzianum and T. virens using cantaloupe and watermelon rinds, respectively. The maximum production of PG and Xyl of T. harzianum and T. virens was recorded at 4–5 days of incubation, 50–66% moisture, temperature 28–35°C and pH 6–7. The influence of supplementary carbon and nitrogen sources was studied. For T. harzianum, lactose enhanced PG activity from 87 to 120 units/g solid, where starch and maltose enhanced Xyl activity from 40 to 55–60 units/g solid for T. virnes. Among the nitrogen sources, ammonium sulphate, ammonium nitrate, yeast extract and urea increased PG activity from 90 to 110–113 units/g solid for T. harzianum. Similarly, ammonium chloride, ammonium sulphate and yeast extract increased Xyl activity from 45 to 55–70 units/g solid for T. virens.  相似文献   

16.
The sugarcane root endophyte Trichoderma virens 223 holds enormous potential as a sustainable alternative to chemical pesticides in the control of sugarcane diseases. Its efficacy as a biocontrol agent is thought to be associated with its production of chitinase enzymes, including N-acetyl-ß-D-glucosaminidases, chitobiosidases and endochitinases. We used targeted gene deletion and RNA-dependent gene silencing strategies to disrupt N-acetyl-ß-D-glucosaminidase and endochitinase activities of the fungus, and to determine their roles in the biocontrol of soil-borne plant pathogens. The loss of N-acetyl-ß-D-glucosaminidase activities was dispensable for biocontrol of the plurivorous damping-off pathogens Rhizoctonia solani and Sclerotinia sclerotiorum, and of the sugarcane pathogen Ceratocystis paradoxa, the causal agent of pineapple disease. Similarly, suppression of endochitinase activities had no effect on R. solani and S. sclerotiorum disease control, but had a pronounced effect on the ability of T. virens 223 to control pineapple disease. Our work demonstrates a critical requirement for T. virens 223 endochitinase activity in the biocontrol of C. paradoxa sugarcane disease, but not for general antagonism of other soil pathogens. This may reflect its lifestyle as a sugarcane root endophyte.  相似文献   

17.
Even though β-1,6-glucanases have been purified from several filamentous fungi, the physiological function has not been conclusively established for any species. In the present study, the role of Tvbgn3, a β-1,6-glucanase from Trichoderma virens, was examined by comparison of wild-type (WT) and transformant strains in which Tvbgn3 was disrupted (GKO) or constitutively overexpressed (GOE). Gene expression analysis revealed induction of Tvbgn3 in the presence of host fungal cell walls, indicating regulation during mycoparasitism. Indeed, while deletion or overexpression of Tvbgn3 had no evident effect on growth and development, GOE and GKO strains showed an enhanced or reduced ability, respectively, to inhibit the growth of the plant pathogen Pythium ultimum compared to results with the WT. The relevance of this activity in the biocontrol ability of T. virens was confirmed in plant bioassays. Deletion of the gene resulted in levels of disease protection that were significantly reduced from WT levels, while GOE strains showed a significantly increased biocontrol capability. These results demonstrate the involvement of β-1,6-glucanase in mycoparasitism and its relevance in the biocontrol activity of T. virens, opening a new avenue for biotechnological applications.  相似文献   

18.
The filamentous fungus Gliocladium virens is able to produce fructooligosaccharides (FOS), fructose-containing sugars, used as functional ingredients to improve nutritional and technological properties of foods. In this work we evaluated FOS production by G. virens when grown in a wide range of sucrose concentrations (10–400 g l?1). High sucrose concentrations increased both biomass and FOS production, including 6-kestose, a trisaccharide comprising β (2 → 6) linked fructosyl units, with enhanced stability and prebiotic activity when compared to the typical FOS β (2 → 1) linked. The highest 6-kestose yield (3 g l?1) was achieved in media containing 150 g l?1 sucrose after 4–5 days of culture, production being 90% greater than in media containing 10, 30, or 50 g l?1 sucrose. After 5 days, FOS production declined markedly, following complete sucrose depletion in the medium. Although most of the β-fructofuranosidases preferentially catalyze sucrose hydrolysis, FOS production in G. virens grown in high sucrose concentration, might be attributed to a reverse hydrolysis by these enzymes. In conclusion, high sucrose concentrations increase growth of G. virens whilst 6-kestose accumulation in the medium seems to be controlled both by specific properties of β-fructofuranosidases and on the sucrose concentration.  相似文献   

19.
Ustilaginoidea virens, which causes rice false smut (RFS), is one of the most detrimental rice fungal diseases and poses a severe threat to rice production and quality. Effectors in U. virens often act as a group of essential virulence factors that play crucial roles in the interaction between host and the pathogen. Thus, the functions of individual effectors in U. virens need to be further explored. Here, we found a small secreted hypersensitive response-inducing protein UVI_02019870 was highly conserved in fungi. Furthermore, we performed Y2H and BiFC assay to demonstrated UVI_02019870 interacted with OsCPL1, which was predicted as a chloroplast precursor to regulate chloroplast signaling pathways. Our data provide a theory for gaining an insight into the molecular mechanisms underlying the UVI_02019870 virulence function.  相似文献   

20.
Protoplast isolation and regeneration from 24 h germinating conidia of Gliocladium catenulatum, G. roseum and G. virens have been optimized. The number of nuclei per cell of four cell types of the Gliocladium spp. was determined. The optimal enzyme combination for protoplast production contained chitinase, lyticase and cellulase onuzaku in 0.5 M mannitol osmoticum. The quantity of protoplasts produced was dependent on the duration of enzymatic digestion, the concentration of germinating condidia and the species of Gliocladium being assayed. A maximum of 11 to 55% of the protoplasts of wild-type Gliocladium spp. and of two double amino acid autoxotrophic mutants of G. roseum (both Met Leu) regenerated to mature, conidiating colonies depending on the regeneration medium utilized and the strain assayed. Protoplasts of G. roseum and G. catenulatum were approximately 4% multinucleate, 56% uninucleate and 40% anucleate. Protoplasts of G. virens were approximately 81% multinucleate, 6% uninucleate and 13% anucleate. Regenerating protoplasts and germinating conidia of G. catenulatum and G. roseum were predominantly uninucleate; those of G. virens were predominantly multinucleate. Conidia of all three Gliocladium spp. were predominantly uninucleate.  相似文献   

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