SEARCH · PubMed Health

Results for “Endophyte”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources

PubMed2002

Peramine alkaloid variation in Neotyphodium-infected Arizona fescue: effects of endophyte and host genotype and environment.

We determined concentrations of peramine, the only alkaloid produced by Neotyphodium-infected (E+) Arizona fescue plants (of the four major types typically assayed in infected grasses), in a long-term field experiment. Four plant genotypes with (E+) and without (experimentally removed, E-) their respective haplotypes (two haplotypes in two plant genotypes) of Neotyphodium were grown in the field under manipulated soil moisture and nutrients. Peramine production required the presence of the endophyte; plants without their endophytes did not contain peramine. Whereas the endophyte was necessary for peramine production, levels of peramine did not vary by Neotyphodium haplotype within plant genotypes. Furthermore, peramine levels did not differ among soil moisture and nutrient treatments, and growth and reproductive measures of the host grass explained little of variation in peramine levels. Instead, peramine levels differed significantly between plant genotypes harboring the same endophyte haplotype, suggesting that plant genotype, rather than endophyte haplotype or environment, largely determines levels of peramine in Arizona fescue. The results suggest that whereas the endophyte is required for peramine production, the plant genotypic background in which the endophyte is embedded, rather than endophyte haplotype or environmental factors, mostly influences peramine levels within this population of Arizona fescue.

Alkaloids↗

PubMed2002

Rainforest endophytes and bioactive products.

An increase in the number of people in the world having health problems caused by certain cancers, drug-resistant bacteria, parasitic protozoans, and fungi has caused alarm. An intensive search for newer and more effective agents to deal with these problems is now underway. Endophytes are a potential source of novel chemistry and biology to assist in helping solve not only human health, but plant and animal health problems also. Endophytes reside in the tissues between living plant cells. The relationship that they establish with the plant varies from symbiotic to bordering on pathogenic. Of all of the world's plants, it seems that only a few grass species have had their complete complement of endophytes studied. As a result, the opportunity to find new and interesting endophytes among the myriad of plants is great. Sometimes extremely unusual and valuable organic substances are produced by these endophytes. These compounds may contribute to the host-microbe relationship. The initial step in dealing with endophytic microorganisms is their successful isolation from plant materials. Then, the isolation and characterization of bioactive substances from culture filtrates is done using bioassay guided fractionation and spectroscopic methods. Some of the more interesting compounds produced by endophytic microbes with which we have dealt are taxol, cryptocin, cryptocandin, jesterone, oocydin, isopestacin, the pseudomycins and ambuic acid. This review discusses an approach for bio-prospecting the rainforests, not only to harvest their endophytic microorganisms, but to eventually build a better understanding of the importance and value they have to humankind.

Anti-Bacterial Agents↗

PubMed1997

Quantitative assessment of in planta distribution of metabolic activity and gene expression of an endophytic fungus.

Using perennial ryegrass infected with an Acremonium transformant carrying the Escherichia coli beta-D-glucuronidase gene (gusA) (GUS system) under control of a constitutive promoter, we have developed methods for the quantitative extraction of endophyte-associated GUS activity from plant material. Fluorometric assays of these extracts allow quantitative assessment of the distribution of endophyte-associated GUS activity within single plants (tillers) with high resolution. Fluorescence microscopy with the dye Imagene Green can in addition visualize individual GUS-expressing hyphae. Since the transformant expresses the GUS gene constitutively, GUS activity can be used as an indicator of in planta endophyte metabolic activity. Using this approach we found that (i) the concentration of endophyte metabolic activity in plant tissue decreases with increasing plant size, (ii) approximately 70% of endophyte metabolic activity present in a plant is located in the leaf sheaths, (iii) basal-apical gradients and lateral (younger to older tissue) gradients of endophyte metabolic activity exist and (iv) basal-apical gradients are established early in leaf development. Our data suggest that the concentration of endophyte in each part of the plant is regulated so that a predetermined threshold of total endophyte activity per plant is not exceeded and a consistent distribution pattern is maintained.

Acremonium↗

PubMed2004

Interaction between endophytic bacteria from citrus plants and the phytopathogenic bacteria Xylella fastidiosa, causal agent of citrus-variegated chlorosis.

AIMS: To isolate endophytic bacteria and Xylella fastidiosa and also to evaluate whether the bacterial endophyte community contributes to citrus-variegated chlorosis (CVC) status in sweet orange (Citrus sinensis [L.] Osbeck cv. Pera). METHODS AND RESULTS: The presence of Xylella fastidiosa and the population diversity of culturable endophytic bacteria in the leaves and branches of healthy, CVC-asymptomatic and CVC-symptomatic sweet orange plants and in tangerine (Citrus reticulata cv. Blanco) plants were assessed, and the in vitro interaction between endophytic bacteria and X. fastidiosa was investigated. There were significant differences in endophyte incidence between leaves and branches, and among healthy, CVC-asymptomatic and CVC-symptomatic plants. Bacteria identified as belonging to the genus Methylobacterium were isolated only from branches, mainly from those sampled from healthy and diseased plants, from which were also isolated X. fastidiosa. CONCLUSIONS: The in vitro interaction experiments indicated that the growth of X. fastidiosa was stimulated by endophytic Methylobacterium extorquens and inhibited by endophytic Curtobacterium flaccumfaciens. SIGNIFICANCE AND IMPACT OF THE STUDY: This work provides the first evidence of an interaction between citrus endophytic bacteria and X. fastidiosa and suggests a promising approach that can be used to better understand CVC disease.

Actinomycetales↗

PubMed1977

Ultrastructural and immunological demonstration of the nodulation of the European Alnus glutinosa (L.) Gaertn. host plant by the North-American Alnus crispa var. mollis Fern. root nodule endophyte.

The inoculation of the European Alnus glutinosa (L.) Gaertn. host plant by a crushed-nodule inoculum, prepared with the North-American Alnus crispa var. mollis Fern. root nodule, was successful. Fluorescein- and ferritin-labelled antibodies, specific against the A. crispa var. mollis root nodule endophyte (Lalonde et al. 1975), demonstrated the idenity of this endophyte in the resulting nodules. The nodulation process of this abnormal host-endophyte system was studied by light and electron microscopy. An excretion of host blebs containing electron-dense polysaccharide material, resulting in the formation of exo-encapsulation threads containing presumptive endophytic bacterial cells, was associated with deformed root hairs. Originating from an exoencapsulation thread, the endophyte penetrates the root hair cell and then migrates as a hypha toward the cortical cells of the root. Its migration in the cortical cells of the primary nodule results in the induction of a lateral root which develops as the true nodule. The ultrastructure of the A. crispa var. mollis endophyte developing in the primary and true nodule of the abnormal A. glutinosa host was similar to the one induced inside its normal A. crispa var. mollis host. The actinomycetal intruder was a branched and septate hypha able to produce septate vesicles. The endophyte was always encapsulated in an electron-dense polysaccharide material surrounded by a host plasma membrane envelope. However, in this abnormal host-endophyte system, the number of primary nodules formed per root system was drastically reduced, and their appearance was delayed by 1 to 2 weeks. The delayed nodules were effective in fixing nitrogen and able to support satisfactory plant growth in a nitrogen-free medium.

Antigens, Bacterial↗

PubMed2000

Overseeding endophytic perennial ryegrass into stands of Kentucky bluegrass to manage bluegrass billbug (Coleoptera: Curculionidae).

Studies were conducted to determine the utility of overseeding endophyte enhanced varieties of perennial ryegrass, Lolium perenne L., into existing stands of Kentucky bluegrass, Poa pratensis L., to manage bluegrass billbug, Sphenophorus parvulus Gyllenhal, larval populations and their damage. Two commercial varieties of endophyte enhanced perennial ryegrass (Repell II and Triple Play) were overseeded at two different rates in the field. S. parvulus larval populations, their damage, and turfgrass composition were monitored over the course of 3 yr. Significantly fewer larvae were found in plots overseeded with Repell II, whereas Triple Play had no significant effect on larval population density. Endophyte infection was confirmed in approximately 58% of all Repell II shoots, whereas only approximately 31% of Triple Play shoots were infected. Regression analysis, using a segmented model, demonstrated that larval populations declined as the proportion of endophyte-infected perennial ryegrass increased. However, no additional reductions in larval population density were achieved in stands containing >40% endophyte-infected perennial ryegrass. Visual damage varied with cultivar, seeding rate, and year, but generally decreased as the proportion of endophyte-infected perennial ryegrass increased. Although seeding rate had an initial effect on turfgrass composition, these differences were not detected after the first year of the study. Results indicate overseeding existing stands of Kentucky bluegrass with endophytic varieties of perennial ryegrass can reduce S. parvulus larval populations and their damage. However, plant genetic characteristics (i.e., different cultivars) may be overriding determinants of many aspects of plant performance including establishment, tolerance to insect feeding, and expression of endophyte-mediated resistance.

Animals↗

PubMed2006

Importance of host plant species, Neotyphodium endophyte isolate, and alkaloids on feeding by Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae.

Three grass host species--tall fescue, Festuca arundinacea Schreber; meadow fescue, Festuca pratensis Hudson; and perennial ryegrass, Lolium perenne L.--each infected with a number of different Neotyphodium endophyte isolates, were investigated for their effects on fall armyworm, Spodoptera frugiperda (J.E. Smith). Alkaloid profiles varied among associations. Choice and no-choice tests comparing feeding and early development of S. frugiperda larvae on endophyte-infected and endophyte-free leaf blade material were performed. Endophyte-mediated resistance to S. frugiperda was greatest in meadow fescue and weakest in tall fescue. Some endophyte isolates, particularly in perennial ryegrass and meadow fescue, had a major effect on feeding and development of S. frugiperda, whereas others had no effect or were only weakly efficacious. In tall fescue, some associations deterred S. frugiperda from feeding in choice tests but had no effect on development, whereas larvae reared on other associations weighed significantly more than control larvae fed endophyte-free grass. It was concluded that the deleterious consequences of endophyte infection were easily masked by other factors in tall fescue. Relative leaf age had no effect on feeding preferences in the three host species. Chemical analysis of herbage from the plants used, and results from a no-choice study using spiked artificial diets, failed to individually implicate any of the major known alkaloids (peramine, lolitrem B, ergovaline, and lolines) in the observed effects on S. frugiperda. Hypotheses explaining these observations, and their impact on creating desirable grass-endophyte associations for use in pastures, are discussed.

Alkaloids↗

PubMed2001

Effects of endophyte status of tall fescue tissues on the earthworm (Eisenia fetida).

A cryptic fungal endophyte, Neotyphodium coenophialum, infects most tall fescue (Festuca arundinacea) pastures in the United States. Cattle, sheep, and horses that consume the endophyte-infected grass can suffer fescue toxicosis caused by toxic alkaloids in the infected plants. The effects of the endophyte on mammalian herbivores have been well documented, but less is known regarding the quality of the grass (infected vs noninfected) as a food material for soil invertebrates. We conducted 21-d tests with earthworms (Eisenia fetida) to determine the nutritional quality of endophyte-infected and noninfected tall fescue leaf and root tissues. Earthworm survival, growth, and reproduction were measured in each treatment combination of tissue type and infection status. Earthworm survival was 100% in all treatments. Tall fescue tissue type (leaf vs root) and infection status (present or absent) both significantly affected E. fetida growth and reproduction. The earthworms grew and had moderate levels of reproduction in replicates containing tall fescue leaf tissue as the sole food source regardless of the endophyte-infection status, but earthworms lost weight and had less reproduction in replicates where tall fescue root tissue was the sole food source. An unexpected effect of infection status on earthworm growth in the tall fescue leaf-tissue treatments was also evident: mean growth of E. fetida with access to endophyte-infected leaf tissue as the sole food source was 3.6-fold greater than mean growth of E. fetida with access to noninfected leaf tissue as the sole food source. Knowledge regarding the relative effects of endophyte status of tall fescue on soil organisms may allow the development of more effective environmental management strategies at sites where tall fescue is being considered for use in phytoremediation or for vegetative cover. Investigators working with tall fescue should be alert to the possibility of endophyte-mediated effects of tall fescue on other organisms and, at a minimum, should provide information regarding the grass's infection status when reporting the results of studies that involve use of tall fescue.

Animals↗

PubMed2000

Alterations in hemograms and serum biochemical analytes of steers after prolonged consumption of endophyte-infected tall fescue.

The objective of the current study was to delineate changes that occur in serum analytes and blood cellular elements in cattle that graze endophyte-infested (Neotyphodium coenophialum) tall fescue. Tall fescue is grown on more than 35 million acres (14.2 million ha) of pasture in the United States, and three-fourths of the pastures are infected with the endophyte at a 60% or greater level. Tall fescue toxicosis caused by endophyte-produced ergot alkaloids continues to be the most important grass-related disease in the United States, in terms of economic loss to animal producers. However, the agronomic attributes of tall fescue make it an attractive forage species because of its ability to withstand cool temperatures, drought, poor soil conditions, and intensive defoliation from herbivore species, including insects. Tall fescue toxicosis is a complex disease and the need exists to understand the mechanisms of the toxic effects in order to institute effective, prophylactic control measures. Our group previously reported changes that occur in serum biochemical analytes of cattle that graze endophyte-infected tall fescue. An additional year's worth of data have been added, strengthening and corroborating these data. Consistent and significant changes associated with tall fescue toxicosis during the 3-yr study included decreased serum concentrations of cholesterol, globulin (increased albumin/globulin ratio), prolactin, total protein, and copper. The activity of alanine aminotransferase was decreased in serum, whereas an increase in serum concentrations of creatinine and total bilirubin occurred. The present report also documents comparative hemograms of cattle that grazed endophyte-infected or endophyte-free tall fescue over a prolonged period. The mean erythrocyte counts were increased in cattle that grazed endophyte-infected tall fescue, whereas mean corpuscular hemoglobin and mean corpuscular volume were decreased, as were mean eosinophil counts. Thus, repeatable changes have been identified that occur in serum biochemical and blood cellular values of cattle grazing endophyte-infected tall fescue that will aid in understanding the pathogenesis of the disease. In addition, these consistently altered parameters can be used to assess the effectiveness of potential prophylactic treatments.

Acremonium↗

PubMed1998

Ammoniation to reduce the toxicity of endophyte-infected tall fescue seed fed to rats.

To assess the efficacy of ammoniation in the detoxification of endophyte-infected tall fescue (Festuca arundinacea Schreb), 40 male Harlan Sprague-Dawley rats were randomly assigned to the following four treatments for 28 d: endophyte-free (E-), endophyte-infected (E+), ammoniated (2% dry matter basis, 7 d) endophyte-free (AE-), and ammoniated endophyte-infected (AE+) tall fescue seed. Total pyrrolizidine alkaloid (N-acetyl and N-formyl loline) and ergovaline contents of endophyte-infected fescue seed were reduced 24 and 54%, respectively, by ammoniation. Endophyte-infected treatment groups had lower (P < 0.01) daily feed intakes (DFI), daily weight gains (DWG), feed efficiencies, and primary serum hemagglutination titers to sheep red blood cell (SRBC) immunization than endophyte-free treatment groups. Performance parameters were higher (P < 0.01) for ammoniated diets in comparison to non-ammoniated diets; however, anti-SRBC titers were not significantly different. When compared to the E+ diet, the AE+ diet increased (P < 0.01) DFI (24%), DWG (41%) and feed efficiency (13%).

Acremonium↗

PubMed1998

Ammoniation to reduce the toxicity of endophyte-infected tall fescue seed fed to rats.

To assess the efficacy of ammoniation in the detoxification of endophyte-infected tall fescue (Festuca arundinacea Schreb.), 40 male Harlan Sprague-Dawley rats were randomly assigned to the following four treatments for 28 d: endophyte-free (E-), endophyte-infected (E+), ammoniated (2% dry matter basis, 7 d) endophyte-free (AE-), and ammoniated endophyte-infected (AE+) tall fescue seed. Total pyrrolizidine alkaloid (N-acetyl and N-formyl loline) and ergovaline contents of endophyte-infected fescue seed were reduced 24 and 54%, respectively, by ammoniation. Endophyte-infected treatment groups had lower (P < 0.01) daily feed intakes (DFI), daily weight gains (DWG), feed effieiencies, and primary serum hemagglutination titers to sheep red blood cell (SRBC) immunization than endophyte-free treatment groups. Performance parameters were higher (P < 0.01) for ammoniated diets in comparison to non-ammoniated die [s; however, anti-SRBC titers were not significantly different. When compared to the E+ diet, the AIE+ diet increased (P < 0.01) DFI (24%), DWG (41%) and feed efficiency (13%).

Acremonium↗

PubMed1990

Effects of ammoniation of endophyte fungus-infested fescue hay on serum prolactin concentration and rectal temperature in beef cattle.

A group of 48 crossbred steers (approx 250 kg each) were used to determine the effects of various diets and treatments on serum prolactin concentrations and rectal temperatures. The steers were randomly assigned to groups fed the following: (1) endophyte fungus-infested fescue hay; (2) ammoniated endophyte fungus-infested fescue hay; (3) endophyte fungus-infested fescue hay plus 1 g of thiabendazole (TBZ)/9.1 kg of body weight at 7-day intervals; (4) ammoniated endophyte fungus-infested fescue hay plus 1 g of TBZ/9.1 kg at 7-day intervals; (5) ground Bermuda grass hay; and (6) endophyte-fungus-free fescue hay. Blood samples for prolactin determinations and rectal temperatures were obtained biweekly beginning on week 3 and continuing through week 9. A significant correlation (P less than 0.05) between low prolactin concentrations and high rectal temperatures in cattle eating endophyte-infested fescue hay was determined; however, as the prolactin concentrations approached normal (control animal) concentrations, this relationship between serum prolactin and rectal temperatures was not observed. Two antifungal agents used in this experiment (thiabendazole and ammonia) appeared to have different effects on the variables measured. Thiabendazole had no significant effect on prolactin concentrations or rectal temperatures of cattle ingesting endophyte-infested fescue hay, whereas ammoniation of this hay induced significantly higher (P less than 0.05) prolactin concentrations and lower rectal temperatures than in steers receiving only endophyte-infested fescue hay. Therefore, ammonia may be valuable not only as an aid in determining the cause of the fescue problem but also as a practical solution to some of the fescue-related economic problems in the cattle industry. Also, prolactin concentrations may be valuable in diagnosing fescue-related problems.

Acremonium↗

PubMed2005

Origin, divergence, and phylogeny of epichloe endophytes of native Argentine grasses.

The epichloë endophytes are systemic, constitutive, and often vertically transmitted fungal symbionts of grass species in subfamily Poöideae. Prior studies indicate that several asexual epichloë endophytes (Neotyphodium species) have evolved directly from sexual (Epichloë) species, whereas others evolved by hybridization between two or more endophyte species. In this paper, we investigate the phylogenies of 27 Neotyphodium spp. isolates from 10 native grass species (in 4 tribes) in 22 populations throughout Argentina. Relationships among these fungi and a worldwide collection of epichloë endophytes were estimated by phylogenetic analysis of sequences from variable portions (mainly introns) of genes for beta-tubulin (tub2) and translation elongation factor 1-alpha (tef1). Most of the Argentine endophyte isolates were interspecific hybrids of Epichloë festucae and E. typhina. Only one isolate was a hybrid of a different ancestry, and three isolates were apparently non-hybrid endophytes. These results indicate that interspecific hybridization, which promotes genetic variation, was common during the evolution of the endophytes of Argentine grasses.

Base Sequence↗

PubMed2006

Effects of ergot alkaloids on food preference and satiety in rabbits, as assessed with gene-knockout endophytes in perennial ryegrass (Lolium perenne).

Neotyphodium species are fungal endophytes best known for their protection of grass hosts and production of bioactive metabolites including ergot alkaloids. Perennial ryegrass-Neotyphodium sp. Lp1 symbiota that have altered ergot alkaloid profiles (resulting from knockouts in two different endophyte genes) were fed, along with controls, to rabbits to test the effects of ergot alkaloids on food preference and satiety. Interestingly, rabbits dramatically preferred plants that were endophyte-infected but free of ergot alkaloids over endophyte-free plants (P = 0.01). Accumulation of ergot alkaloids of the clavine class counteracted the added appeal of endophyte-infected plants. In satiety tests, consumption of ergovaline (the ultimate ergot pathway product in wild-type endophyte), but not of several other ergot alkaloids, during an initial meal had a negative effect on subsequent rabbit chow consumption (P < 0.05). The data indicate that clavines were sufficient to reduce the appeal of endophyte-infected grasses, whereas only ergovaline reduced appetite.

Animals↗

PubMed1994

Evolutionary diversification of fungal endophytes of tall fescue grass by hybridization with Epichloë species.

The mutualistic associations of tall fescue (Festuca arundinacea) with seed-borne fungal symbionts (endophytes) are important for fitness of the grass host and its survival under biotic and abiotic stress. The tall fescue endophytes are asexual relatives of biological species (mating populations) of genus Epichloë (Clavicipitaceae), sexual fungi that cause grass choke disease. Isozyme studies have suggested considerable genetic diversity among endophytes of tall fescue. Phylogenetic relationships among seven isolates from tall fescue, three from meadow fescue (a probable ancestor of tall fescue), and nine Epichloë isolates from other host species were investigated by comparing sequences of noncoding segments of the beta-tubulin (tub2) and rRNA (rrn) genes. Whereas each Epichloë isolate and meadow fescue endophyte had only a single tub2 gene, most tall fescue endophytes had two or three distinct tub2 copies. Phylogenetic analysis of tub2 sequences indicated that the presence of multiple copies in the tall fescue endophytes was a consequence of hybridization with Epichloë species. At least three hybridization events account for the distribution and relationships of tub2 genes. These results suggest that interspecific hybridization is the major cause of genetic diversification of the tall fescue endophytes.

Amino Acid Sequence↗

PubMed2006

Bacterial endophytes and their interactions with hosts.

Recent molecular studies on endophytic bacterial diversity have revealed a large richness of species. Endophytes promote plant growth and yield, suppress pathogens, may help to remove contaminants, solubilize phosphate, or contribute assimilable nitrogen to plants. Some endophytes are seedborne, but others have mechanisms to colonize the plants that are being studied. Bacterial mutants unable to produce secreted proteins are impaired in the colonization process. Plant genes expressed in the presence of endophytes provide clues as to the effects of endophytes in plants. Molecular analysis showed that plant defense responses limit bacterial populations inside plants. Some human pathogens, such as Salmonella spp., have been found as endophytes, and these bacteria are not removed by disinfection procedures that eliminate superficially occurring bacteria. Delivery of endophytes to the environment or agricultural fields should be carefully evaluated to avoid introducing pathogens.

Bacteria↗

PubMed2006

Endophytic fungus decreases plant virus infections in meadow ryegrass (Lolium pratense).

We studied the effects of fungal endophyte infection of meadow ryegrass (Lolium pratense=Festuca pratensis) on the frequency of the barley yellow dwarf virus (BYDV). The virus is transferred by aphids, which may be deterred by endophyte-origin alkaloids within the plant. In our experiment, we released viruliferous aphid vectors on endophyte-infected and endophyte-free plants in a common garden. The number of aphids and the percentage of BYDV infections were lower in endophyte-infected plants compared to endophyte-free plants, indicating that endophyte infection may protect meadow ryegrass from BYDV infections.

Animals↗

PubMed2002

Environmental conditions and host genotype direct genetic diversity of Venturia ditricha, a fungal endophyte of birch trees.

We investigated whether genetic variation of a common foliar endophyte of birch trees, Venturia ditricha, is affected by environmental conditions or host genotype. Fungal samples were collected from 10 half-sibling families of mountain birch (Betula pubescens ssp. czerepanovii) grown in two environmental conditions with different daily average temperatures: a forested river valley and an adjacent open tundra (altitudinal difference 180 m). Genetic analysis of V. ditricha isolates was done using random amplified microsatellite polymerase chain reaction. We found that host genotypes, along with prevailing environmental conditions, influence the probability of infection by particular endophyte genotypes. The most susceptible host genotypes were highly infected with genetically similar endophyte genotypes, whereas the most resistant trees were poorly infected and they were infected by genetically dissimilar endophytes. Our results also showed environment-host genotype interactions, suggesting that the susceptibility of the host to a particular endophyte genotype may change in natural environments when environmental conditions are changed. It appears that a particular endophyte genotype needs to find the right host genotype for a successful infection. There are many host genotypes in natural stands; this means, from the point of view of the fungus, the environment is heterogeneous. Thus, under the influence of birch tree genotypes, genetically differentiated subgroups of the endophytic fungus may be formed in different environments.

Ascomycota↗