Publications by authors named "James F White"

46 Publications

Fungal Endophytes as Efficient Sources of Plant-Derived Bioactive Compounds and Their Prospective Applications in Natural Product Drug Discovery: Insights, Avenues, and Challenges.

Microorganisms 2021 Jan 19;9(1). Epub 2021 Jan 19.

Department of Botany, MMV, Banaras Hindu University, Varanasi 221005, India.

Fungal endophytes are well-established sources of biologically active natural compounds with many producing pharmacologically valuable specific plant-derived products. This review details typical plant-derived medicinal compounds of several classes, including alkaloids, coumarins, flavonoids, glycosides, lignans, phenylpropanoids, quinones, saponins, terpenoids, and xanthones that are produced by endophytic fungi. This review covers the studies carried out since the first report of taxol biosynthesis by endophytic in 1993 up to mid-2020. The article also highlights the prospects of endophyte-dependent biosynthesis of such plant-derived pharmacologically active compounds and the bottlenecks in the commercialization of this novel approach in the area of drug discovery. After recent updates in the field of 'omics' and 'one strain many compounds' (OSMAC) approach, fungal endophytes have emerged as strong unconventional source of such prized products.
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http://dx.doi.org/10.3390/microorganisms9010197DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7833388PMC
January 2021

A Gnotobiotic Model to Examine Plant and Microbiome Contributions to Survival under Arsenic Stress.

Microorganisms 2020 Dec 26;9(1). Epub 2020 Dec 26.

Área de Biodiversidad y Conservación, Departamento de Biología, Geología, Física y Química Inorgánica, Universidad Rey Juan Carlos, 28933 Móstoles, Spain.

So far, the relative importance of the plant and its microbiome in the development of early stages of plant seedling growth under arsenic stress has not been studied. To test the role of endophytic bacteria in increasing plant success under arsenic stress, gnotobiotic seeds of were inoculated with two endophytic bacteria: MC-K1 (PGPB and As resistant bacteria) and sp. MC-D3A (non-helper and non-As resistant bacteria) and an endobacteria mixture. In holobiotic seedlings (with seed-vectored microbes intact), neither the capacity of germination nor development of roots and lateral hairs was affected at 125 μM As(V). However, in gnotobiotic seedlings, the plants are negatively impacted by absence of a microbiome and presence of arsenic, resulting in reduced growth of roots and root hairs. The inoculation of a single PGPB (-MCK1) shows a tendency to the recovery of the plant, both in arsenic enriched and arsenic-free media, while the inoculation with sp. does not help in the recovery of the plants. Inoculation with a bacterial mixture allows recovery of plants in arsenic free media; however, plants did not recover under arsenic stress, probably because of a bacterial interaction in the mixture.
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http://dx.doi.org/10.3390/microorganisms9010045DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7823691PMC
December 2020

Characterization and Pathogenicity of Species on cv. Congo in Gansu Province, China.

Plant Dis 2020 Oct 20;104(10):2571-2584. Epub 2020 Aug 20.

State Key Laboratory of Grassland Agro-Ecosystems; Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture and Rural Affairs; Engineering Research Center of Grassland Industry, Ministry of Education; Gansu Tech Innovation Center of Western China Grassland Industry; Center for Grassland Microbiome; College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730020, China.

In recent years in China, leaf spot caused by species has been an emerging disease of cv. Congo. From 2016 to 2019, typical symptoms, appearing as circular or ovoid, sunken, and brown lesions with a yellow halo, were commonly observed on cv. Congo in and around Lanzhou, Gansu Province, China. Conidiomata were often visible on infected leaf surfaces. Leaf disease incidence was approximately 5 to 20%. A total of 126 single-spored isolates were obtained from leaf lesions. Multilocus phylogenetic relationships were analyzed based on seven genomic loci (ITS, , , , , , and ) and the morphological characters of the isolates determined. These isolates were identified as three species in this study. A further 93 isolates, accounting for 74% of all isolates, were described as new species and named as sp. nov. after the host plant genus name, ; another two isolates were named as sp. nov. based on phylogenetic and morphological relativeness to ; the other 31 isolates, belonging to the species complex, were identified as a known species-. Both novel species and belong to the species complex. Pathogenicity tests by both spray and point inoculations confirmed that all three species could infect leaves of cv. Congo. For spray inoculation, the mean infection rate of leaves on the three species was only 4.7% (0 to 12%), and the size on lesions was mostly 1 to 2 mm in length. For point inoculation, 30 days after nonwounding inoculation, the infection rate on leaves was 0 to 35%; in wounding inoculation, the infection rate of leaves was 35 to 65%; wounding in healthy leaves greatly enhanced the pathogenicity of these three species to cv. Congo; however, the sizes of lesions among the three species were not significantly different. To our knowledge, this is the first report of species associated with anthracnose diseases on cv. Congo. Results obtained in this study will assist the disease prevention and appropriate management strategies.
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http://dx.doi.org/10.1094/PDIS-09-19-1952-REDOI Listing
October 2020

Characterization of Species Causing Brown Leaf Spot on Italian Ryegrass () in Southwestern China.

Plant Dis 2020 Jul 12;104(7):1900-1907. Epub 2020 May 12.

State Key Laboratory of Grassland Agro-Ecosystems; Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture and Rural Affairs; Engineering Research Center of Grassland Industry, Ministry of Education; Gansu Tech Innovation Center of Western China Grassland Industry; Center for Grassland Microbiome; College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730020, China.

Drechslera leaf spot (DLS) caused by () species is one of the most serious diseases affecting Italian ryegrass () in China. Between 2015 and 2018, this disease was observed in three Italian ryegrass fields in the province of Sichuan, China. Average leaf disease incidence was approximately 1 to 12% but could range up to 100%. Symptoms appeared as brown or tan spots surrounded by a yellow halo, or brown to dark brown net blotch; subsequently, spots increased in number and size, and they later covered a large area of leaf, eventually causing leaf death. In this study, 86 strains of fungi were isolated from leaf lesions of Italian ryegrass. Coupled with phylogenetic analysis of the internal transcribed spacer region, partial 28S ribosomal RNA gene, and glyceraldehyde-3-phosphate dehydrogenase gene, morphological characteristics showed that and are associated with Italian ryegrass in southwest China. Pathogenicity tests confirmed that both species can infect Italian ryegrass, causing leaf spot, whereas the virulence of the two species differed; showed lower pathogenicity to Italian ryegrass. This is the first time that these two species were formally reported on Italian ryegrass based on both morphological and molecular characters. Overall, this study improves knowledge of the species associated with Italian ryegrass and provides a foundation for control of this disease in the future.
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http://dx.doi.org/10.1094/PDIS-07-19-1457-REDOI Listing
July 2020

Isolation and identification of L-asparaginase-producing endophytic fungi from the Asteraceae family plant species of Iran.

PeerJ 2020 14;8:e8309. Epub 2020 Jan 14.

Department of Plant Production, Gonbad Kavous University, Gonbad Kavous, Iran.

L-asparaginase is an important anticancer enzyme that is used in the first line treatment of acute lymphoblastic leukemia. This study was conducted to isolate L-asparaginase-producing endophytic fungi from medicinal plants of family Asteraceae. Seven healthy medicinal plants from family Asteraceae were selected for the isolation of endophytic fungi using standard surface sterilization techniques. A total of 837 isolates belonging to 84 species were comprised of the stem (55.6%), leaf (31.1%), root (10.6%) and flower (2.7%). Initial screening of L-asparaginase-producing endophytes was performed by qualitative plate assay on modified Czapex dox's agar medium. L-asparaginase activity of fungal endophytes was quantified by the nesslerization method. Identification of endophytic fungi was performed using both morphological characteristics and phylogenetic analyses of DNA sequence data including ribosomal DNA regions of ITS (Internal transcribed spacer) and LSU (partial large subunit rDNA), TEF1 (Translation Elongation Factor) and TUB (-tubulin). Of the 84 isolates, 38 were able to produce L-asparaginase and their L-asparaginase activities were between 0.019 and 0.492 unit/mL with being the most potent. L-asparaginase-producing endophytes were identified as species of and . This study showed that endophytic fungi from Asteraceae members have a high L-asparaginase-producing potential and they can be used as an alternative source for production of anticancer enzymes.
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http://dx.doi.org/10.7717/peerj.8309DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6968492PMC
January 2020

16S rRNA metagenomic analysis of the bacterial community associated with turf grass seeds from low moisture and high moisture climates.

PeerJ 2020 10;8:e8417. Epub 2020 Jan 10.

Department of Plant Biology, Rutgers, The State University of New Jersey, New Brunswick, NJ, USA.

Turfgrass investigators have observed that plantings of grass seeds produced in moist climates produce seedling stands that show greater stand evenness with reduced disease compared to those grown from seeds produced in dry climates. Grass seeds carry microbes on their surfaces that become endophytic in seedlings and promote seedling growth. We hypothesize that incomplete development of the microbiome associated with the surface of seeds produced in dry climates reduces the performance of seeds. Little is known about the influence of moisture on the structure of this microbial community. We conducted metagenomic analysis of the bacterial communities associated with seeds of three turf species (, , and ) from low moisture (LM) and high moisture (HM) climates. The bacterial communities were characterized by Illumina high-throughput sequencing of 16S rRNA V3-V4 regions. We performed seed germination tests and analyzed the correlations between the abundance of different bacterial groups and seed germination at different taxonomy ranks. Climate appeared to structure the bacterial communities associated with seeds. LM seeds vectored mainly Proteobacteria (89%). HM seeds vectored a denser and more diverse bacterial community that included Proteobacteria (50%) and Bacteroides (39%). At the genus level, (20%), (13%), (12%), (12%) and (11%) were the major genera in the bacterial communities regardless of climate conditions. , and dominated LM seeds, while and dominated HM seeds. The species of turf seeds did not appear to influence bacterial community composition. The seeds of the three turf species showed a core microbiome consisting of 27 genera from phyla Actinobacteria, Bacteroidetes, Patescibacteria and Proteobacteria. Differences in seed-vectored microbes, in terms of diversity and density between high and LM climates, may result from effects of moisture level on the colonization of microbes and the development of microbe community on seed surface tissues (adherent paleas and lemmas). The greater diversity and density of seed vectored microbes in HM climates may benefit seedlings by helping them tolerate stress and fight disease organisms, but this dense microbial community may also compete with seedlings for nutrients, slowing or modulating seed germination and seedling growth.
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http://dx.doi.org/10.7717/peerj.8417DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6956778PMC
January 2020

Characterization, Phylogenetic Analyses, and Pathogenicity of Species on in Sichuan Province, China.

Plant Dis 2019 Oct 7;103(10):2624-2633. Epub 2019 Aug 7.

State Key Laboratory of Grassland Agro-ecosystems, Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture and Rural Affairs, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, 730020, P.R. China.

Brown spot disease caused by species was found on leaves of mulberry ( L.) in Dujiangyan, Sichuan Province, China. Fungal isolates from leaf lesions were identified as six species based on morphological characteristics and DNA analysis of the combined sequences ITS, , , , , and . These included , , , , subsp. , and . Results showed that the most important causal agent of mulberry anthracnose was , causing typical brown necrotic spots or streaks, followed by , , and subsp. , whereas the two other species ( and ) showed no pathogenicity to mulberry. This study is the first report of these species associated with mulberry in China.
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http://dx.doi.org/10.1094/PDIS-06-18-0938-REDOI Listing
October 2019

Review: Endophytic microbes and their potential applications in crop management.

Pest Manag Sci 2019 Oct 27;75(10):2558-2565. Epub 2019 Jul 27.

U.S. Geological Survey, Great Lakes Science Center, Cleveland, OH, USA.

Endophytes are microbes (mostly bacteria and fungi) present asymptomatically in plants. Endophytic microbes are often functional in that they may carry nutrients from the soil into plants, modulate plant development, increase stress tolerance of plants, suppress virulence in pathogens, increase disease resistance in plants, and suppress development of competitor plant species. Endophytic microbes have been shown to: (i) obtain nutrients in soils and transfer nutrients to plants in the rhizophagy cycle and other nutrient-transfer symbioses; (ii) increase plant growth and development; (iii) reduce oxidative stress of hosts; (iv) protect plants from disease; (v) deter feeding by herbivores; and (vi) suppress growth of competitor plant species. Because of the effective functions of endophytic microbes, we suggest that endophytic microbes may significantly reduce use of agrochemicals (fertilizers, fungicides, insecticides, and herbicides) in the cultivation of crop plants. The loss of endophytic microbes from crop plants during domestication and long-term cultivation could be remedied by transfer of endophytes from wild relatives of crops to crop species. Increasing atmospheric carbon dioxide levels could reduce the efficiency of the rhizophagy cycle due to repression of reactive oxygen used to extract nutrients from microbes in roots. © 2019 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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http://dx.doi.org/10.1002/ps.5527DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6771842PMC
October 2019

, an Endophyte That Establishes a Nutrient-Transfer Symbiosis With Banana Plants and Protects Against the Black Sigatoka Pathogen.

Front Microbiol 2019 7;10:804. Epub 2019 May 7.

Department of Chemistry, Universidad Autónoma de Guadalajara, Zapopan, Mexico.

Banana ( spp.) is an important crop worldwide, but black Sigatoka disease caused by the fungus threatens fruit production. In this work, we examined the potential of the endophytes of banana plants and , as antagonists of and support plant growth in nutrient limited soils by N-transfer. The two bacterial isolates were identified by MALDI-TOF mass spectrometry and corroborated by 16S rRNA sequence analysis. Both bacteria were positive for beneficial traits such as N-fixation, indole acetic acid production, phosphate solubilization, negative for 1-aminocyclopropane 1-carboxylic acid deaminase and were antagonistic to . To measure the effects on plant growth, the two plant bacteria and an strain (as non-endophyte), were inoculated weekly for 60 days as active cells (AC) and heat-killed cells (HKC) into plant microcosms without nutrients and compared to a water only treatment, and a mineral nutrients solution (MMN) treatment. Bacterial treatments increased growth parameters and prevented accelerated senescence, which was observed for water and mineral nutrients solution (MMN) treatments used as controls. Plants died after the first 20 days of being irrigated with water; irrigation with MMN enabled plants to develop some new leaves, but plants lost weight (-30%) during the same period. Plants treated with bacteria showed good growth, but AC treated plants had significantly greater biomass than the HKC. After 60 days, plants inoculated with AC showed intracellular bacteria within root cells, suggesting that a stable symbiosis was established. To evaluate the transference of organic N from bacteria into the plants, the 3 bacteria were grown with NHCl or NaNO as the nitrogen source. The N transferred from bacteria to plant tissues was measured by pheophytin isotopomer abundance. The relative abundance of the isotopomers 872.57, 873.57, 874.57, 875.57, 876.57 unequivocally demonstrated that plants acquired N atoms directly from bacterial cells, using them as a source of N, to support plant growth in restricted nutrient soils. might be a new alternative to promote growth and health of banana crops.
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http://dx.doi.org/10.3389/fmicb.2019.00804DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6513882PMC
May 2019

spp. Associated with Smooth Crabgrass () Seed Inhibit Competitor Plant Species.

Microorganisms 2019 May 21;7(5). Epub 2019 May 21.

Centre of Advanced Study in Botany, Banaras Hindu University, Varanasi 211005, India.

(Schreb.) Schreb. ex Muhl. and L. are competitive, early successional species which are usually considered weeds in agricultural and turfgrass systems. Bacteria and fungi associated with and seed may contribute to their competitiveness by antagonizing competitor forbs, and were studied in axenic culture. spp. were the most common bacterial isolate of seed, while and spp. were common fungal isolates. A variety of species were collected from non-surface sterilized . Certain spp. isolates were antagonistic to competitor forbs . All bacterial isolates that affected mortality were isolated from seed while none of the isolates affected mortality. Two selected bacterial isolates identified as were evaluated further on (a competitor forb) and (a competitor grass) alone and in combination with a sp. fungus. These bacteria alone caused >65% seedling mortality but did not affect seedling mortality. These experiments demonstrate that associated with seeds is antagonistic to competitor forbs in axenic culture. The weedy character of could at least in part stem from the possession of bacteria that are antagonistic to competitor species.
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http://dx.doi.org/10.3390/microorganisms7050143DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6560401PMC
May 2019

Rhizophagy Cycle: An Oxidative Process in Plants for Nutrient Extraction from Symbiotic Microbes.

Microorganisms 2018 Sep 17;6(3). Epub 2018 Sep 17.

U.S. Geological Survey, Great Lakes Science Center, 1451 Green Road, Ann Arbor, MI 48105-2807, USA.

In this paper, we describe a mechanism for the transfer of nutrients from symbiotic microbes (bacteria and fungi) to host plant roots that we term the 'rhizophagy cycle.' In the rhizophagy cycle, microbes alternate between a root intracellular endophytic phase and a free-living soil phase. Microbes acquire soil nutrients in the free-living soil phase; nutrients are extracted through exposure to host-produced reactive oxygen in the intracellular endophytic phase. We conducted experiments on several seed-vectored microbes in several host species. We found that initially the symbiotic microbes grow on the rhizoplane in the exudate zone adjacent the root meristem. Microbes enter root tip meristem cells-locating within the periplasmic spaces between cell wall and plasma membrane. In the periplasmic spaces of root cells, microbes convert to wall-less protoplast forms. As root cells mature, microbes continue to be subjected to reactive oxygen (superoxide) produced by NADPH oxidases (NOX) on the root cell plasma membranes. Reactive oxygen degrades some of the intracellular microbes, also likely inducing electrolyte leakage from microbes-effectively extracting nutrients from microbes. Surviving bacteria in root epidermal cells trigger root hair elongation and as hairs elongate bacteria exit at the hair tips, reforming cell walls and cell shapes as microbes emerge into the rhizosphere where they may obtain additional nutrients. Precisely what nutrients are transferred through rhizophagy or how important this process is for nutrient acquisition is still unknown.
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http://dx.doi.org/10.3390/microorganisms6030095DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6164190PMC
September 2018

Fungal Disease Prevention in Seedlings of Rice (Oryza sativa) and Other Grasses by Growth-Promoting Seed-Associated Endophytic Bacteria from Invasive Phragmites australis.

Microorganisms 2018 Mar 8;6(1). Epub 2018 Mar 8.

Department of Plant Biology, Rutgers University, New Brunswick, NJ 08901, USA.

Non-cultivated plants carry microbial endophytes that may be used to enhance development and disease resistance of crop species where growth-promoting and protective microbes may have been lost. During seedling establishment, seedlings may be infected by several fungal pathogens that are seed or soil borne. Several species of , and other water moulds cause seed rots during germination. blights of seedlings are also very common and significantly affect seedling development. In the present study we screened nine endophytic bacteria isolated from the seeds of invasive by inoculating onto rice, Bermuda grass (), or annual bluegrass () seeds to evaluate plant growth promotion and protection from disease caused by . We found that three bacteria belonging to genus spp. (SLB4-, SLB6- sp. and SY1- sp.) promoted seedling development, including enhancement of root and shoot growth, and stimulation of root hair formation. These bacteria were also found to increase phosphate solubilization in in vitro experiments. sp. (SY1) significantly protected grass seedlings from infection. In co-culture experiments, strain SY1 strongly inhibited fungal pathogens with 85.71% growth inhibition of , 86.33% growth inhibition of sp. and 82.14% growth inhibition of sp. Seedlings previously treated with bacteria were found much less infected by in comparison to non-treated controls. On microscopic observation we found that bacteria appeared to degrade fungal mycelia actively. Metabolite products of strain SY1 in agar were also found to inhibit fungal growth on nutrient media. sp. (SY1) was found to produce antifungal volatiles. Polymerase chain reaction (PCR) amplification using specific primers for pyrrolnitirin synthesis and HCN (hydrogen cyanide) production suggested presence of genes for both compounds in the genome of SY1. HCN was detected in cultures of SY1. We conclude that microbes from non-cultivated plants may provide disease protection and promote growth of crop plants.
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http://dx.doi.org/10.3390/microorganisms6010021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5874635PMC
March 2018

Bacterial communities of three plant species from Pb-Zn contaminated sites and plant-growth promotional benefits of endophytic Microbacterium sp. (strain BXGe71).

J Hazard Mater 2019 05 6;370:225-231. Epub 2018 Feb 6.

Medical School, Kunming University of Science and Technology, Kunming 650500,China. Electronic address:

The endophytic bacterial community of two hyperaccumulators (Arabis alpine, Dysphania ambrosioides) and Veronica ciliate was investigated by Illumina sequencing technology. In addition, the culturable endophytic bacteria (EB) were isolated and their plant-growth promotion capabilities were studied. A dataset consisting of 221,075 filtered high-quality and classifiable unique 16S rDNA gene tags, and an average of 36,846 tags with a mean length of 464-bp for each sample was generated. In total, 10801 different operational taxonomic units (OTUs) were detected, belonging to 18 bacterial phyla, 41 classes, 91 orders, 135 families, and 215 genera. Pseudomonas was the most dominant genus in both shoots and roots of the two hyperaccumulators, making up 81.56% and 81.13%, 41.60% and 77.06% of the total number of OTUs, respectively. However, both Chao 1 and Shannon indices of EB of the two hyperaccumulators were significantly lower than those of V. ciliate (P <. 05), except the Shannon index of D. ambrosioides shoots. The endophytic bacterial community of roots and shoots of A. alpine showed greater similarity with that of D. ambrosioides roots (12 km away), and clustered to one group in dendrogram, in clear contrast to that of V. ciliate, which grew closer to A. alpine (60 m away). Combining results of soil and plant analyses, we suggest that the soil properties, especially heavy metal concentration, may influence the plants endophytic bacterial community composition. Pot experiments showed that the strain BXGe71 (Microbacterium sp.) from A. alpine significantly enhanced host plants' growth under multi-heavy metal (HM) stress (P < .05, t-test).
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http://dx.doi.org/10.1016/j.jhazmat.2018.02.003DOI Listing
May 2019

Identification of the fungal endophyte of (American beachgrass) as .

PeerJ 2018 22;6:e4300. Epub 2018 Jan 22.

Department of Plant Biology, Rutgers, The State University of New Jersey, New Brunswick, NJ, United States of America.

The grass (American beachgrass) is known to host an endophyte of the genus . Based on morphological characteristics it was originally identified as var. and is currently designated as var. . However, the species has not previously been identified based on DNA sequence data. Based on phylogenetic placement of beta-tubulin and translation elongation factor 1-alpha DNA sequences the endophyte is identified as a member of rather than .
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http://dx.doi.org/10.7717/peerj.4300DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5784578PMC
January 2018

Syntrophic imbalance and the etiology of bacterial endoparasitism diseases.

Authors:
James F White

Med Hypotheses 2017 Sep 15;107:14-15. Epub 2017 Jul 15.

Department Plant Biology, Rutgers University, New Brunswick, NJ 08901, United States. Electronic address:

This article outlines the proposed 'syntrophic imbalance hypothesis' for etiology of bacterial endoparasitism diseases. This hypothesis involves microbes (archaea and bacteria) that exist in human body biofilms in syntrophic associations, where bacteria ferment nutrients to produce short chain fatty acids (SCFAs) that are used by methanogenic archaeons to produce methane. Overgrowth of archaea on human tissues (e.g., in association with intestines, teeth or lungs) results in excessive removal of SCFAs from the biofilms and this triggers bacteria in the free-living biofilm state to convert to the endoparasitic state and become intracellular in host cells where they incite inflammation and disease. The proposed model provides the mechanism to explain dysbiosis etiology of several human diseases, including gingivitis, leaky gut syndrome, Crohn's disease, irritable bowel syndrome, among others.
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http://dx.doi.org/10.1016/j.mehy.2017.07.015DOI Listing
September 2017

Paper-based plasma sanitizers.

Proc Natl Acad Sci U S A 2017 05 1;114(20):5119-5124. Epub 2017 May 1.

Department of Mechanical and Aerospace Engineering, Rutgers University, Piscataway, NJ 08854;

This work describes disposable plasma generators made from metallized paper. The fabricated plasma generators with layered and patterned sheets of paper provide a simple and flexible format for dielectric barrier discharge to create atmospheric plasma without an applied vacuum. The porosity of paper allows gas to permeate its bulk volume and fuel plasma, while plasma-induced forced convection cools the substrate. When electrically driven with oscillating peak-to-peak potentials of ±1 to ±10 kV, the paper-based devices produced both volume and surface plasmas capable of killing microbes. The plasma sanitizers deactivated greater than 99% of and greater than 99.9% of cells with 30 s of noncontact treatment. Characterization of plasma generated from the sanitizers revealed a detectable level of UV-C (1.9 nW⋅cm⋅nm), modest surface temperature (60 °C with 60 s of activation), and a high level of ozone (13 ppm with 60 s of activation). These results deliver insights into the mechanisms and suitability of paper-based substrates for active antimicrobial sanitization with scalable, flexible sheets. In addition, this work shows how paper-based generators are conformable to curved surfaces, appropriate for kirigami-like "stretchy" structures, compatible with user interfaces, and suitable for sanitization of microbes aerosolized onto a surface. In general, these disposable plasma generators represent progress toward biodegradable devices based on flexible renewable materials, which may impact the future design of protective garments, skin-like sensors for robots or prosthetics, and user interfaces in contaminated environments.
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http://dx.doi.org/10.1073/pnas.1621203114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5441778PMC
May 2017

Overlooked competing asexual and sexually typified generic names of with recommendations for their use or protection.

IMA Fungus 2016 Dec 29;7(2):289-308. Epub 2016 Nov 29.

Department of Plant Biology & Pathology, Rutgers University, 59 Dudley Rd., New Brunswick, NJ 08901, USA.

With the change to one scientific name for fungal species, numerous papers have been published with recommendations for use or protection of competing generic names in major groups of ascomycetes. Although genera in each group of fungi were carefully considered, some competing generic names were overlooked. This paper makes recommendations for additional competing genera not considered in previous papers. Chairs of relevant Working Groups of the ICTF were consulted in the development of these recommendations. A number of generic names need protection, specifically over , over over , over , over and , over , over , over , over over , and over and The following new combinations are made: and . Finally, one new species name, , is introduced to validate an earlier name, and the conservation of with a new type, , is recommended.
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http://dx.doi.org/10.5598/imafungus.2016.07.02.09DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5159600PMC
December 2016

Interactions between cranberries and fungi: the proposed function of organic acids in virulence suppression of fruit rot fungi.

Front Microbiol 2015 14;6:835. Epub 2015 Aug 14.

Department of Plant Biology and Pathology, Rutgers University New Brunswick, NJ, USA.

Cranberry fruit are a rich source of bioactive compounds that may function as constitutive or inducible barriers against rot-inducing fungi. The content and composition of these compounds change as the season progresses. Several necrotrophic fungi cause cranberry fruit rot disease complex. These fungi remain mostly asymptomatic until the fruit begins to mature in late August. Temporal fluctuations and quantitative differences in selected organic acid profiles between fruit of six cranberry genotypes during the growing season were observed. The concentration of benzoic acid in fruit increased while quinic acid decreased throughout fruit development. In general, more rot-resistant genotypes (RR) showed higher levels of benzoic acid early in fruit development and more gradual decline in quinic acid levels than that observed in the more rot-susceptible genotypes. We evaluated antifungal activities of selected cranberry constituents and found that most bioactive compounds either had no effects or stimulated growth or reactive oxygen species (ROS) secretion of four tested cranberry fruit rot fungi, while benzoic acid and quinic acid reduced growth and suppressed secretion of ROS by these fungi. We propose that variation in the levels of ROS suppressive compounds, such as benzoic and quinic acids, may influence virulence by the fruit rot fungi. Selection for crops that maintain high levels of virulence suppressive compounds could yield new disease resistant varieties. This could represent a new strategy for control of disease caused by necrotrophic pathogens that exhibit a latent or endophytic phase.
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http://dx.doi.org/10.3389/fmicb.2015.00835DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4536381PMC
August 2015

Collaboration between grass seedlings and rhizobacteria to scavenge organic nitrogen in soils.

AoB Plants 2015 Jan 6;7. Epub 2015 Jan 6.

Department of Plant Biology and Pathology, Rutgers University, New Brunswick, NJ, USA.

Plants require nitrogen (N) to make proteins, nucleic acids and other biological molecules. It is widely accepted that plants absorb inorganic forms of N to fill their needs. However, recently it has become clear that plants also have the capacity to absorb organic N from soils. In this paper we describe a new kind of symbiosis involving seed-vectored rhizobacteria and grasses that is targeted at enhancing acquisition of organic N from soils. Our proposal is based on results of experiments on seedlings of grass species Festuca arundinacea Schreb., Lolium perenne L. and Poa annua L. that suggest: (i) seed-vectored rhizobacteria colonize seedling roots and influence their development; (ii) reactive oxygen secretion by seedling roots plays a role in organic N procurement by denaturing microbial proteins in the vicinity of roots (daytime activity); and (iii) plant root and microbial proteases degrade denatured proteins prior to absorption by roots (night-time activity). This research involved the following types of studies: (i) seedling root development experiments with and without rhizobacteria on a variety of substrates in agarose media and (ii) isotopic N-tracking experiments to evaluate the absorption into seedlings of N obtained from degradation of proteins. We hypothesize that grasses, in particular, are adapted to scavenge organic N from soils through application of this 'oxidative nitrogen scavenging' symbiosis with rhizobacteria, and their soil-permeating root systems. This newly discovered symbiosis in grass species could lead to new ways to cultivate and manage grasses to enhance efficiency of N utilization and reduce applications of inorganic fertilizers.
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http://dx.doi.org/10.1093/aobpla/plu093DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4313791PMC
January 2015

Endophytic Bacillus spp. produce antifungal lipopeptides and induce host defence gene expression in maize.

Microbiol Res 2015 Mar 28;172:79-87. Epub 2014 Nov 28.

Department of Plant Biology and Pathology, Rutgers University, New Brunswick, NJ 08901, United States. Electronic address:

Endophytes are mutualistic symbionts within healthy plant tissues. In this study we isolated Bacillus spp. from seeds of several varieties of maize. Bacillus amyloliquifaciens or Bacillus subtilis were found to be present in all maize varieties examined in this study. To determine whether bacteria may produce antifungal compounds, generally lipopeptides in Bacillus spp., bacterial cultures were screened for production of lipopeptides. Lipopeptides were extracted by acid precipitation from liquid cultures of Bacillus spp. Lipopeptide extracts from Bacillus spp. isolated from Indian popcorn and yellow dent corn showed inhibitory activity against Fusarium moniliforme at 500μg per disk. Using MALDI-TOF mass spectrometry we detected the presence of antifungal iturin A, fengycin and bacillomycin in these isolates. PCR amplification also showed the presence of genes for iturin A and fengycin. B. subtilis (SG_JW.03) isolated from Indian popcorn showed strong inhibition of Arabidopsis seed mycoflora and enhanced seedling growth. We tested for the induction of defence gene expression in the host plant after treatment of plants with B. subtilis (SG_JW.03) and its lipopeptide extract using RT-qPCR. Roots of Indian popcorn seedlings treated with a suspension of B. subtilis (SG_JW.03) showed the induction of pathogenesis-related genes, including PR-1 and PR-4, which relate to plant defence against fungal pathogens. The lipopeptide extract alone did not increase the expression of these pathogenesis-related genes. Based on our study of maize endophytes, we hypothesize that, bacterial endophytes that naturally occur in many maize varieties may function to protect hosts by secreting antifungal lipopeptides that inhibit pathogens as well as inducing the up-regulation of pathogenesis-related genes of host plants (systemic acquired resistance).
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http://dx.doi.org/10.1016/j.micres.2014.11.004DOI Listing
March 2015

Nitrogen acquisition in Agave tequilana from degradation of endophytic bacteria.

Sci Rep 2014 Nov 6;4:6938. Epub 2014 Nov 6.

Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, 05508-000, São Paulo, SP, Brazil.

Plants form symbiotic associations with endophytic bacteria within tissues of leaves, stems, and roots. It is unclear whether or how plants obtain nitrogen from these endophytic bacteria. Here we present evidence showing nitrogen flow from endophytic bacteria to plants in a process that appears to involve oxidative degradation of bacteria. In our experiments we employed Agave tequilana and its seed-transmitted endophyte Bacillus tequilensis to elucidate organic nitrogen transfer from (15)N-labeled bacteria to plants. Bacillus tequilensis cells grown in a minimal medium with (15)NH4Cl as the nitrogen source were watered onto plants growing in sand. We traced incorporation of (15)N into tryptophan, deoxynucleosides and pheophytin derived from chlorophyll a. Probes for hydrogen peroxide show its presence during degradation of bacteria in plant tissues, supporting involvement of reactive oxygen in the degradation process. In another experiment to assess nitrogen absorbed as a result of endophytic colonization of plants we demonstrated that endophytic bacteria potentially transfer more nitrogen to plants and stimulate greater biomass in plants than heat-killed bacteria that do not colonize plants but instead degrade in the soil. Findings presented here support the hypothesis that some plants under nutrient limitation may degrade and obtain nitrogen from endophytic microbes.
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http://dx.doi.org/10.1038/srep06938DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4221784PMC
November 2014

Occurrence of Bacillus amyloliquefaciens as a systemic endophyte of vanilla orchids.

Microsc Res Tech 2014 Nov 25;77(11):874-85. Epub 2014 Jul 25.

Department of Plant Biology and Pathology, Rutgers University, New Brunswick, New Jersey.

We report the occurrence of Bacillus amyloliquefaciens in vanilla orchids (Vanilla phaeantha) and cultivated hybrid vanilla (V. planifolia × V. pompona) as a systemic bacterial endophyte. We determined with light microscopy and isolations that tissues of V. phaeantha and the cultivated hybrid were infected by a bacterial endophyte and that shoot meristems and stomatal areas of stems and leaves were densely colonized. We identified the endophyte as B. amyloliquefaciens using DNA sequence data. Since additional endophyte-free plants and seed of this orchid were not available, additional studies were performed on surrogate hosts Amaranthus caudatus, Ipomoea tricolor, and I. purpurea. Plants of A. caudatus inoculated with B. amyloliquefaciens demonstrated intracellular colonization of guard cells and other epidermal cells, confirming the pattern observed in the orchids. Isolations and histological studies suggest that the bacterium may penetrate deeply into developing plant tissues in shoot meristems, forming endospores in maturing tissues. B. amyloliquefaciens produced fungal inhibitors in culture. In controlled experiments using morning glory seedlings we showed that the bacterium promoted seedling growth and reduced seedling necrosis due to pathogens. We detected the gene for phosphopantetheinyl transferase (sfp), an enzyme in the pathway for production of antifungal lipopeptides, and purified the lipopeptide "surfactin" from cultures of the bacterium. We hypothesize that B. amyloliquefaciens is a robust endophyte and defensive mutualist of vanilla orchids. Whether the symbiosis between this bacterium and its hosts can be managed to protect vanilla crops from diseases is a question that should be evaluated in future research.
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http://dx.doi.org/10.1002/jemt.22410DOI Listing
November 2014

Epichloë spp. associated with grasses: new insights on life cycles, dissemination and evolution.

Mycologia 2014 Mar-Apr;106(2):181-201

Epichloë species with their asexual states are specialized fungi associated with cool-season grasses. they grow endophytically in tissues of aerial parts of host plants to form systemic and mostly asymptomatic associations. Their life cycles may involve vertical transmission through host seeds and/or horizontal transmission from one plant to other plants of the same species through fungal propagules. Vertical transmission has been well studied, but comparatively little research has been done on horizontal dissemination. The goal of this review is to provide new insights on modes of dissemination of systemic grass endophytes. The review addresses recent progress in research on (i) the process of growth of Epichloë endophytes in the host plant tissues, (ii) the types and development of reproductive structures of the endophyte, (iii) the role of the reproductive structures in endophyte dissemination and host plant infection processes and (iv) some ecological and evolutionary implications of their modes of dissemination. Research in the Epichloë grass endophytes has accelerated in the past 25 y and has demonstrated the enormous complexity in endophyte-grass symbioses. There still remain large gaps in our understanding of the role and functions of these fungi in agricultural systems and understanding the functions, ecology and evolution of these endophytes in natural grass populations.
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http://dx.doi.org/10.3852/106.2.181DOI Listing
July 2014

Hydrogen peroxide staining to visualize intracellular bacterial infections of seedling root cells.

Microsc Res Tech 2014 Aug 13;77(8):566-73. Epub 2014 May 13.

Department of Plant Biology and Pathology, Rutgers University, New Brunswick, New Jersey.

Visualization of bacteria in living plant cells and tissues is often problematic due to lack of stains that pass through living plant cell membranes and selectively stain bacterial cells. In this article, we report the use of 3,3'-diaminobenzidine tetrachloride (DAB) to stain hydrogen peroxide associated with bacterial invasion of eukaryotic cells. Tissues were counterstained with aniline blue/lactophenol to stain protein in bacterial cells. Using this staining method to visualize intracellular bacterial (Burkholderia gladioli) colonization of seedling roots of switch grass (Panicum virgatum), we compared bacterial free seedling roots and those inoculated with the bacterium. To further assess application of the technique in multiple species of vascular plants, we examined vascular plants for seedling root colonization by naturally occurring seed-transmitted bacteria. Colonization by bacteria was only observed to occur within epidermal (including root hairs) and cortical cells of root tissues, suggesting that bacteria may not be penetrating deeply into root tissues. DAB/peroxidase with counter stain aniline blue/lactophenol was effective in penetration of root cells to selectively stain bacteria. Furthermore, this stain combination permitted the visualization of the bacterial lysis process. Before any evidence of H2 O2 staining, intracellular bacteria were seen to stain blue for protein content with aniline blue/lactophenol. After H2 O2 staining became evident, bacteria were often swollen, without internal staining by aniline blue/lactophenol; this suggests loss of protein content. This staining method was effective for seedling root tissues; however, it was not effective at staining bacteria in shoot tissues due to poor penetration.
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http://dx.doi.org/10.1002/jemt.22375DOI Listing
August 2014

Singlet molecular oxygen generation by light-activated DHN-melanin of the fungal pathogen Mycosphaerella fijiensis in black Sigatoka disease of bananas.

PLoS One 2014 19;9(3):e91616. Epub 2014 Mar 19.

Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil.

In pathogenic fungi, melanin contributes to virulence, allowing tissue invasion and inactivation of the plant defence system, but has never been implicated as a factor for host cell death, or as a light-activated phytotoxin. Our research shows that melanin synthesized by the fungal banana pathogen Mycosphaerella fijiensis acts as a virulence factor through the photogeneration of singlet molecular oxygen O2 (1Δg). Using analytical tools, including elemental analysis, ultraviolet/infrared absorption spectrophometry and MALDI-TOF mass spectrometry analysis, we characterized both pigment content in mycelia and secreted to the culture media as 1,8-dihydroxynaphthalene (DHN)-melanin type compound. This is sole melanin-type in M. fijiensis. Isolated melanins irradiated with a Nd:YAG laser at 532 nm produced monomol light emission at 1270 nm, confirming generation of O2 (1Δg), a highly reactive oxygen specie (ROS) that causes cellular death by reacting with all cellular macromolecules. Intermediary polyketides accumulated in culture media by using tricyclazole and pyroquilon (two inhibitors of DHN-melanin synthesis) were identified by ESI-HPLC-MS/MS. Additionally, irradiation at 532 nm of that mixture of compounds and whole melanized mycelium also generated O2 (1Δg). A pigmented-strain generated more O2 (1Δg) than a strain with low melanin content. Banana leaves of cultivar Cavendish, naturally infected with different stages of black Sigatoka disease, were collected from field. Direct staining of the naturally infected leaf tissues showed the presence of melanin that was positively correlated to the disease stage. We also found hydrogen peroxide (H2O2) but we cannot distinguish the source. Our results suggest that O2 (1Δg) photogenerated by DHN-melanin may be involved in the destructive effects of Mycosphaerella fijiensis on banana leaf tissues. Further studies are needed to fully evaluate contributions of melanin-mediated ROS to microbial pathogenesis.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0091616PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3960117PMC
December 2014

Nomenclatural realignment of Neotyphodium species with genus Epicholë.

Mycologia 2014 Mar-Apr;106(2):202-15

Nomenclatural rule changes in the International Code of Nomenclature for algae, fungi and plants, adopted at the 18th International Botanical Congress in Melbourne, Australia, in 2011, provide for a single name to be used for each fungal species. The anamorphs of Epichloë species have been classified in genus Neotyphodium, the form genus that also includes most asexual Epichloë descendants. A nomenclatural realignment of this monophyletic group into one genus would enhance a broader understanding of the relationships and common features of these grass endophytes. Based on the principle of priority of publication we propose to classify all members of this clade in the genus Epichloë. We have reexamined classification of several described Epichloë and Neotyphodium species and varieties and propose new combinations and states. In this treatment we have accepted 43 unique taxa in Epichloë, including distinct species, subspecies, and varieties. We exclude from Epichloë the two taxa Neotyphodium starrii, as nomen dubium, and Neotyphodium chilense, as an unrelated taxon.
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http://dx.doi.org/10.3852/13-251DOI Listing
July 2014

A proposed mechanism for nitrogen acquisition by grass seedlings through oxidation of symbiotic bacteria.

Symbiosis 2012 Jul 5;57(3):161-171. Epub 2012 Oct 5.

Department of Plant Biology and Pathology, Rutgers University, New Brunswick, NJ USA.

In this paper we propose and provide evidence for a mechanism, oxidative nitrogen scavenging (ONS), whereby seedlings of some grass species may extract nitrogen from symbiotic diazotrophic bacteria through oxidation by plant-secreted reactive oxygen species (ROS). Experiments on this proposed mechanism employ tall fescue (Festuca arundinaceae) seedlings to elucidate features of the oxidative mechanism. We employed 15N(2) gas assimilation experiments to demonstrate nitrogen fixation, direct microscopic visualization of bacteria on seedling surfaces to visualize the bacterial oxidation process, reactive oxygen probes to test for the presence of H(2)O(2) and cultural experiments to assess conditions under which H(2)O(2) is secreted by seedlings. We also made surveys of the seedlings of several grass species to assess the distribution of the phenomenon of microbial oxidation in the Poaceae. Key elements of the proposed mechanism for nitrogen acquisition in seedlings include: 1) diazotrophic bacteria are vectored on or within seeds; 2) at seed germination bacteria colonize seedling roots and shoots; 3) seedling tissues secrete ROS onto bacteria; 4) bacterial cell walls, membranes, nucleic acids, proteins and other biological molecules are oxidized; 5) nitrates and/or smaller fragments of organic nitrogen-containing molecules resulting from oxidation may be absorbed by seedling tissues and larger peptide fragments may be further processed by secreted or cell wall plant proteases until they are small enough for transport into cells. Hydrogen peroxide secretion from seedling roots and bacterial oxidation was observed in several species in subfamily Pooideae where seeds possessed adherent paleas and lemmas, but was not seen in grasses that lacked this feature or long-cultivated crop species.
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http://dx.doi.org/10.1007/s13199-012-0189-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3473182PMC
July 2012

New molecular markers for fungal phylogenetics: two genes for species-level systematics in the Sordariomycetes (Ascomycota).

Mol Phylogenet Evol 2012 Sep 22;64(3):500-12. Epub 2012 May 22.

Department of Plant Biology and Pathology, Rutgers University, 59 Dudley Rd, New Brunswick, NJ 08901, USA.

Although significant progress has been made resolving deep branches of the fungal tree of life, many fungal systematists are interested in species-level questions to both define species and assess fungal biodiversity. Fungal genome sequences are a useful resource to systematic biologists for developing new phylogenetic markers that better represent the whole genome. Here we report primers for two newly identified single-copy protein-coding genes, FG1093 and MS204, for use with ascomycetes. Although fungi were the focus of this study, this methodological approach could be easily applied to marker development for studies of other organisms. The tests used here to assess phylogenetic informativeness are computationally rapid, require only rudimentary datasets to evaluate existing or newly developed markers, and can be applied to other non-model organisms to assist in experimental design of phylogenetic studies. Phylogenetic utility of the markers was tested in two genera, Gnomoniopsis and Ophiognomonia (Gnomoniaceae, Diaporthales). The phylogenetic performance of β-tubulin, ITS, and tef-1α was compared with FG1093 and MS204. Phylogenies inferred from FG1093 and MS204 were largely in agreement with β-tubulin, ITS, and tef-1α although some topological conflict was observed. Resolution and support for branches differed based on the combination of markers used for each genus. Based on two independent tests of phylogenetic performance, FG1093 and MS204 were determined to be equal to or better than β-tubulin, ITS, and tef-1α in resolving species relationships. Differences were found in site-specific rate of evolution in all five markers. In addition, isolates from 15 orders and 22 families of Ascomycota were screened using primers for FG1093 and MS204 to demonstrate primer utility across a wide diversity of ascomycetes. The primer sets for the newly identified genes FG1093 and MS204 and methods used to develop them are useful additions to the ascomycete systematists' toolbox.
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http://dx.doi.org/10.1016/j.ympev.2012.05.005DOI Listing
September 2012

New species, phylogeny, host-associations and geographic distribution of genus Cryptosporella (Gnomoniaceae, Diaporthales).

Mycologia 2011 Mar-Apr;103(2):379-99. Epub 2010 Oct 7.

Systematic Mycology & Microbiology Laboratory, USDA-ARS, Room 304, B011A, 10300 Baltimore Avenue, Beltsville, Maryland 20705, USA.

The phylogeny of Cryptosporella is revised to include recently discovered species. Eight species new to science are described and two new combinations are proposed, raising the total number of species accepted in Cryptosporella to 19. The species delimitation and phylogeny for Cryptosporella are determined based on analyses of DNA sequences from three genes (β-tubulin, ITS and tef1-α), comparative morphology of sexual structures on their host substrate, and host associations. The inferred phylogeny suggests that Cryptosporella has speciated primarily on Betulaceae with 16 species occurring on hosts in that plant family. The host range of most species seems to be narrow with nine species reported from a single host species or subspecies and seven species occurring on plants within a single host genus. A key to species is provided. The known distribution of Cryptosporella is expanded to mountain cloud forests of the provinces of Chiriquí in Panama and Tucumán in Argentina.
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http://dx.doi.org/10.3852/10-134DOI Listing
May 2011

Light converts endosymbiotic fungus to pathogen, influencing seedling survival and niche-space filling of a common tropical tree, Iriartea deltoidea.

PLoS One 2011 Jan 31;6(1):e16386. Epub 2011 Jan 31.

Department of Plant Biology and Pathology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, New Jersey, United States of America.

Pathogens are hypothesized to play an important role in the maintenance of tropical forest plant species richness. Notably, species richness may be promoted by incomplete filling of niche space due interactions of host populations with their pathogens. A potentially important group of pathogens are endophytic fungi, which asymptomatically colonize plants and are diverse and abundant in tropical ecosystems. Endophytes may alter competitive abilities of host individuals and improve host fitness under stress, but may also become pathogenic. Little is known of the impacts of endophytes on niche-space filling of their hosts.Here we evaluate how a widespread fungal endophyte infecting a common tropical palm influences its recruitment and survival in natural ecosystems, and whether this impact is modulated by the abiotic environment, potentially constraining host niche-space filling. Iriartea deltoidea dominates many wet lowland Neotropical forests. Diplodia mutila is a common asymptomatic endophyte in mature plants; however, it causes disease in some seedlings. We investigated the effects of light availability on D. mutila disease expression.We found I. deltoidea seedlings to preferentially occur under shady conditions. Correspondingly, we also found that high light triggers endophyte pathogenicity, while low light favors endosymbiotic development, constraining recruitment of endophyte-infested seedlings to shaded understory by reducing seedling survival in direct light. Pathogenicity of D. mutila under high light is proposed to result from light-induced production of H(2)O(2) by the fungus, triggering hypersensitivity, cell death, and tissue necrosis in the palm. This is the first study to demonstrate that endophytes respond to abiotic factors to influence plant distributions in natural ecosystems; and the first to identify light as a factor influencing where an endophyte is placed on the endosymbiont-pathogen continuum. Our findings show that pathogens can indeed constrain niche-space filling of otherwise successful tropical plant species, providing unoccupied niche space for other species.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0016386PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3031546PMC
January 2011