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Zhang W, Forester NT, Applegate ER, Liu X, Johnson LJ. High-affinity iron uptake is required for optimal Epichloë festucae colonization of Lolium perenne and seed transmission. Mol Plant Pathol 2023; 24:1430-1442. [PMID: 37477276 PMCID: PMC10576175 DOI: 10.1111/mpp.13379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 06/14/2023] [Accepted: 06/26/2023] [Indexed: 07/22/2023]
Abstract
Epichloë festucae uses a siderophore-mediated system to acquire iron, which is important to maintain endophyte-grass symbioses. Here we investigate the roles of the alternative iron acquisition system, reductive iron assimilation (RIA), via disruption of the fetC gene, which encodes a multicopper ferroxidase, either alone (i.e., ΔfetC) or in combination with disruption of the gene sidA, which encodes a siderophore biosynthesis enzyme (i.e., ΔfetC/ΔsidA). The phenotypic characteristics of these mutants were compared to ΔsidA and wild-type (WT) strains during growth under axenic culture conditions (in culture) and in symbiosis with the host grass, perennial ryegrass (in planta). Under iron deficiency, the colony growth rate of ΔfetC was slightly slower than that of WT, while the growth of ΔsidA and ΔfetC/ΔsidA mutants was severely suppressed. Siderophore analyses indicated that ΔfetC mutants hyperaccumulate ferriepichloënin A (FEA) at low iron concentrations and ferricrocin and FEA at higher iron concentrations. When compared to WT, all mutant strains displayed hyperbranching hyphal structures and a reduced ratio of Epichloë DNA to total DNA in planta. Furthermore, host colonization and vertical transmission through infection of the host seed were significantly reduced in the ΔfetC/ΔsidA mutants, confirming that high-affinity iron uptake is a critical process for Epichloë transmission. Thus, RIA and siderophore iron uptake are complementary systems required for the maintenance of iron metabolism, fungal growth, and symbiosis between E. festucae and perennial ryegrass.
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Affiliation(s)
- Wei Zhang
- AgResearch Limited, Grasslands Research CentrePalmerston NorthNew Zealand
| | | | - Emma R. Applegate
- AgResearch Limited, Grasslands Research CentrePalmerston NorthNew Zealand
| | - Xinqi Liu
- AgResearch Limited, Grasslands Research CentrePalmerston NorthNew Zealand
| | - Linda J. Johnson
- AgResearch Limited, Grasslands Research CentrePalmerston NorthNew Zealand
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2
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Zhang W, Forester NT, Chettri P, Heilijgers M, Mace WJ, Maes E, Morozova Y, Applegate ER, Johnson RD, Johnson LJ. Characterization of the Biosynthetic Gene Cluster for the Ribosomally Synthesized Cyclic Peptide Epichloëcyclins in Epichloë festucae. J Agric Food Chem 2023; 71:13965-13978. [PMID: 37704203 PMCID: PMC10540207 DOI: 10.1021/acs.jafc.3c03073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 08/14/2023] [Accepted: 08/16/2023] [Indexed: 09/15/2023]
Abstract
The various grass-induced epichloëcyclins of the Epichloë spp. are ribosomally synthesized and post-translationally modified peptides (RiPPs), produced as small, secreted cyclopeptides from a single gene, gigA. Here, four clustered and coregulated genes (gigA, gigB, gigC, and kexB) with predicted roles in epichloëcyclin production in Epichloë festucae were evaluated through gene disruption. Subsequent chemical analysis indicates that GigB is a DUF3328 domain-containing protein associated with cyclization of epichloëcyclins; GigC is a methyltransferase enzyme responsible for N-methylation of desmethylepichloëcyclins; and KexB is a subtilisin-like enzyme, partly responsible for the propeptide cleavage of epichloëcyclin intermediates. Symbiotic effects on the host phenotype were not observed for gigA, gigC, or kexB mutants, although ΔgigB infection correlated with increased host tiller height and biomass, while only ΔkexB exhibited an effect on endophyte morphology. Disrupting epichloëcyclin biosynthesis showed negligible influence on the biosynthesis of E. festucae-associated alkaloids. Epichloëcyclins may perform other secondary metabolism functions in Epichloë and other fungi.
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Affiliation(s)
- Wei Zhang
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Natasha T. Forester
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Pranav Chettri
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Maurice Heilijgers
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Wade J. Mace
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Evelyne Maes
- Lincoln
Research Centre, AgResearch Limited, Lincoln 7608, New Zealand
| | - Yulia Morozova
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Emma R. Applegate
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Richard D. Johnson
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
| | - Linda J. Johnson
- Grasslands
Research Centre, AgResearch Limited, Palmerston North 4442, New Zealand
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3
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Kumar S, Johnson LJ, Teasdale S, Morozova Y, de Bonth ACM, Jauregui R, Hannaford R, Card SD. Survey of the Endophytic Bacteria Inhabiting Wild Daucus Seed Using 16S rRNA Gene Amplicon Sequencing. Microbiol Resour Announc 2023:e0014023. [PMID: 37154770 DOI: 10.1128/mra.00140-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023] Open
Abstract
We report a preliminary survey of the endophytic bacterial microbiota of seed from wild carrot (Daucus carota) using 16S rRNA gene amplicon sequencing. Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria were the most abundant phyla detected, while Bacillus, Massilia, Paenibacillus, Pantoea, Pseudomonas, Rhizobium, Sphingomonas, and Xanthomonas were the most abundant genera.
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Affiliation(s)
- Sandeep Kumar
- AgResearch Ltd., Grasslands Research Centre, Palmerston North, New Zealand
| | - Linda J Johnson
- AgResearch Ltd., Grasslands Research Centre, Palmerston North, New Zealand
| | - Suliana Teasdale
- AgResearch Ltd., Grasslands Research Centre, Palmerston North, New Zealand
| | - Yulia Morozova
- AgResearch Ltd., Grasslands Research Centre, Palmerston North, New Zealand
| | | | - Ruy Jauregui
- AgResearch Ltd., Grasslands Research Centre, Palmerston North, New Zealand
| | - Rina Hannaford
- AgResearch Ltd., Grasslands Research Centre, Palmerston North, New Zealand
| | - Stuart D Card
- AgResearch Ltd., Grasslands Research Centre, Palmerston North, New Zealand
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4
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Zhang W, Forester NT, Moon CD, Maclean PH, Gagic M, Arojju SK, Card SD, Matthew C, Johnson RD, Johnson LJ, Faville MJ, Voisey CR. Epichloë seed transmission efficiency is influenced by plant defense response mechanisms. Front Plant Sci 2022; 13:1025698. [PMID: 36340377 PMCID: PMC9635450 DOI: 10.3389/fpls.2022.1025698] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 09/30/2022] [Indexed: 06/16/2023]
Abstract
Asexual Epichloë are endophytic fungi that form mutualistic symbioses with cool-season grasses, conferring to their hosts protection against biotic and abiotic stresses. Symbioses are maintained between grass generations as hyphae are vertically transmitted from parent to progeny plants through seed. However, endophyte transmission to the seed is an imperfect process where not all seeds become infected. The mechanisms underpinning the varying efficiencies of seed transmission are poorly understood. Host gene expression in response to Epichloë sp. LpTG-3 strain AR37 was examined within inflorescence primordia and ovaries of high and low endophyte transmission genotypes within a single population of perennial ryegrass. A genome-wide association study was conducted to identify population-level single nucleotide polymorphisms (SNPs) and associated genes correlated with vertical transmission efficiency. For low transmitters of AR37, upregulation of perennial ryegrass receptor-like kinases and resistance genes, typically associated with phytopathogen detection, comprised the largest group of differentially expressed genes (DEGs) in both inflorescence primordia and ovaries. DEGs involved in signaling and plant defense responses, such as cell wall modification, secondary metabolism, and reactive oxygen activities were also abundant. Transmission-associated SNPs were associated with genes for which gene ontology analysis identified "response to fungus" as the most significantly enriched term. Moreover, endophyte biomass as measured by quantitative PCR of Epichloë non-ribosomal peptide synthetase genes, was significantly lower in reproductive tissues of low-transmission hosts compared to high-transmission hosts. Endophyte seed-transmission efficiency appears to be influenced primarily by plant defense responses which reduce endophyte colonization of host reproductive tissues.
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Affiliation(s)
- Wei Zhang
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
- School of Agriculture and Environment, Massey University, Palmerston North, New Zealand
| | - Natasha T. Forester
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Christina D. Moon
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Paul H. Maclean
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Milan Gagic
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Sai Krishna Arojju
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Stuart D. Card
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Cory Matthew
- School of Agriculture and Environment, Massey University, Palmerston North, New Zealand
| | - Richard D. Johnson
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Linda J. Johnson
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Marty J. Faville
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Christine R. Voisey
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
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5
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Persson A, Ecounomou Lundeberg JEL, Dziubinski MD, Slusarczyk MS, Grotek AG, Johnson LJ, Engstrom GE. Heart rate during sinus rhythm predicts paroxysmal atrial fibrillation on 30-day mobile cardiac telemetry monitoring. Eur Heart J 2022. [DOI: 10.1093/eurheartj/ehac544.381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
Background
Low mean heart rate at ambulatory ECG monitoring and low resting heart rate are both predictors of later incident atrial fibrillation (AF). The aim of this study is to determine whether mean heart rate at ambulatory ECG is a predictor of paroxysmal AF that can be detected with extended ambulatory ECG registration.
Methods
We included all patients who recorded 2–30 full days of ambulatory ECG using a full disclosure mobile cardiac telemetry device in USA 2019–2020, and without AF on the first full day of registration (n=18,220, mean age 64.4 years, 57.2% women). The association between mean heart rate on the first day and the occurrence of paroxysmal AF (≥30 seconds duration) during subsequent up to 30 day ECG recording was analysed using logistic regression models adjusted for age, sex and duration of ECG recording, according to tertiles of mean heart rate (39–66, 67–76 and >77 beats per minute) as well as modelled using restricted cubic splines.
Results
During a median registration duration of 16 days there were 1,290 cases of paroxysmal AF (7.1%). More paroxysmal AF occurred in the lower tertiles of mean heart rate (11.2% in tertile 1, 6.2% in tertile 2, and 4.4% in tertile 3). After adjustment, low mean heart rate was associated with a higher risk of AF (OR 1.69, 95% CI 1.47–1.93 p<0.001 for tertile 1 vs tertile 2, and OR 1.84, 95% CI 1.58–2.15, p<0.001 for tertile 1 vs tertile 3). Cubic spline curves indicated that lowest risks of AF were seen among subjects with a mean heart rate ≈80 beats per minute.
Conclusion
Low mean heart rate at 24hECG predicts detection of paroxysmal AF during extended ≤30 day ambulatory ECG monitoring.
Funding Acknowledgement
Type of funding sources: Foundation. Main funding source(s): Swedish Heart Lung foundationSwedish Society for Medical Research
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Miller TA, Hudson DA, Johnson RD, Singh JS, Mace WJ, Forester NT, Maclean PH, Voisey CR, Johnson LJ. Dissection of the epoxyjanthitrem pathway in Epichloë sp. LpTG-3 strain AR37 by CRISPR gene editing. Front Fungal Biol 2022; 3:944234. [PMID: 37746172 PMCID: PMC10512260 DOI: 10.3389/ffunb.2022.944234] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Accepted: 07/18/2022] [Indexed: 09/26/2023]
Abstract
Epichloë festucae var. lolii and Epichloë sp. LpTG-3 are filamentous fungal endophytes of perennial ryegrass (Lolium perenne) that have a substantial impact on New Zealand's agricultural economy by conferring biotic advantages to the host grass. Overall, Epichloë endophytes contribute NZ$200 million to the economy annually, with strain AR37 estimated to contribute NZ$3.6 billion to the New Zealand economy over a 20-year period. This strain produces secondary metabolites, including epoxyjanthitrems, which are a class of indole diterpenes, associated with the observed effects of AR37 on livestock and insect pests. Until very recently, AR37 was intractable to genetic modification but this has changed with the application of CRISPR-Cas9 based gene editing techniques. In this paper, gene inactivation by CRISPR-Cas9 was used to deconvolute the genetic basis for epoxyjanthitrem biosynthesis, including creating an AR37 strain that has been edited to remove the biosynthesis of all indole diterpenes. We show that gene editing of Epichloë can be achieved without off-target events or introduction of foreign DNA (footprint-less) through an AMA1-based plasmid that simultaneously expresses the CRISPR-Cas9 system and selectable marker. Genetic modification events in these transformants were investigated through genome sequencing and in planta chemistry.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Linda J. Johnson
- Grasslands Research Centre, AgResearch, Palmerston North, New Zealand
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7
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Bastías DA, Applegate ER, Johnson LJ, Card SD. Factors controlling the effects of mutualistic bacteria on plants associated with fungi. Ecol Lett 2022; 25:1879-1888. [PMID: 35810320 PMCID: PMC9544109 DOI: 10.1111/ele.14073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 05/31/2022] [Accepted: 06/21/2022] [Indexed: 11/29/2022]
Abstract
Plants interacting with mutualistic fungi (MF) or antagonistic fungi (AF) can form associations with bacteria. We assessed whether the performance gain conferred by mutualistic bacteria to fungal-associated plants is affected by the interaction between symbiont traits, type of bacterial-protective traits against AF and abiotic/biotic stresses. Results showed that (A) performance gain conferred by bacteria to MF-associated plants was greater when symbionts promoted distinct rather than similar plant functions, (B) bacterial-based alleviation of the AF's negative effect on plants was independent of the type of protective trait, (C) bacteria promoted a greater performance of symbiotic plants in presence of biotic, but not abiotic, stress compared to stress-free situations. The plant performance gain was not affected by any fungal-bacterial trait combination but optimised when bacteria conferred resistance traits in biotic stress situations. The effects of bacteria on fungal-associated plants were controlled by the interaction between the symbionts' functional traits and the relationship between bacterial traits and abiotic/biotic stresses.
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Affiliation(s)
- Daniel A Bastías
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Emma R Applegate
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Linda J Johnson
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
| | - Stuart D Card
- Grasslands Research Centre, AgResearch Limited, Palmerston North, New Zealand
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8
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Liu Q, Johnson LJ, Applegate ER, Arfmann K, Jauregui R, Larking A, Mace WJ, Maclean P, Walker T, Johnson RD. Identification of Genetic Diversity, Pyrrocidine-Producing Strains and Transmission Modes of Endophytic Sarocladium zeae Fungi from Zea Crops. Microorganisms 2022; 10:microorganisms10071415. [PMID: 35889134 PMCID: PMC9316807 DOI: 10.3390/microorganisms10071415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 07/12/2022] [Accepted: 07/12/2022] [Indexed: 12/10/2022] Open
Abstract
Genotyping by sequencing (GBS) was used to reveal the inherent genetic variation within the haploid fungi Sarocladium zeae isolated from diverse Zea germplasm, including modern Zea mays and its wild progenitors—the teosintes. In accordance with broad host relationship parameters, GBS analysis revealed significant host lineages of S. zeae genetic diversity, indicating that S. zeae genetic variation may associate with different evolutionary histories of host species or varieties. Based on a recently identified PKS-NRPS gene responsible for pyrrocidine biosynthesis in S. zeae fungi, a novel PCR assay was developed to discriminate pyrrocidine-producing S. zeae strains. This molecular method for screening bioactive strains of S. zeae is complementary to other approaches, such as chemical analyses. An eGFP-labelled S. zeae strain was also developed to investigate the endophytic transmission of S. zeae in Z. mays seedlings, which has further improved our understanding of the transmission modes of S. zeae endophytes in maize tissues.
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9
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Berry D, Lee K, Winter D, Mace W, Becker Y, Nagabhyru P, Treindl AD, Bogantes EV, Young CA, Leuchtmann A, Johnson LJ, Johnson RD, Cox MP, Schardl CL, Scott B. Cross-species transcriptomics identifies core regulatory changes differentiating the asymptomatic asexual and virulent sexual life cycles of grass-symbiotic Epichloë fungi. G3 (Bethesda) 2022; 12:jkac043. [PMID: 35191483 PMCID: PMC8982410 DOI: 10.1093/g3journal/jkac043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Accepted: 02/07/2022] [Indexed: 02/04/2023]
Abstract
Fungi from the genus Epichloë form systemic endobiotic infections of cool season grasses, producing a range of host-protective natural products in return for access to nutrients. These infections are asymptomatic during vegetative host growth, with associations between asexual Epichloë spp. and their hosts considered mutualistic. However, the sexual cycle of Epichloë spp. involves virulent growth, characterized by the envelopment and sterilization of a developing host inflorescence by a dense sheath of mycelia known as a stroma. Microscopic analysis of stromata revealed a dramatic increase in hyphal propagation and host degradation compared with asymptomatic tissues. RNAseq was used to identify differentially expressed genes in asymptomatic vs stromatized tissues from 3 diverse Epichloë-host associations. Comparative analysis identified a core set of 135 differentially expressed genes that exhibited conserved transcriptional changes across all 3 associations. The core differentially expressed genes more strongly expressed during virulent growth encode proteins associated with host suppression, digestion, adaptation to the external environment, a biosynthetic gene cluster, and 5 transcription factors that may regulate Epichloë stroma formation. An additional 5 transcription factor encoding differentially expressed genes were suppressed during virulent growth, suggesting they regulate mutualistic processes. Expression of biosynthetic gene clusters for natural products that suppress herbivory was universally suppressed during virulent growth, and additional biosynthetic gene clusters that may encode production of novel host-protective natural products were identified. A comparative analysis of 26 Epichloë genomes found a general decrease in core differentially expressed gene conservation among asexual species, and a specific decrease in conservation for the biosynthetic gene cluster expressed during virulent growth and an unusual uncharacterized gene.
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Affiliation(s)
- Daniel Berry
- Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
| | - Kate Lee
- Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
| | - David Winter
- Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
| | - Wade Mace
- AgResearch Ltd, Grasslands Research Centre, Palmerston North 4442, New Zealand
| | - Yvonne Becker
- Institute for Epidemiology and Pathogen Diagnostics, Julius Kühn Institute, Federal Research Centre for Cultivated Plants, 38104 Braunschweig, Germany
| | - Padmaja Nagabhyru
- Department of Plant Pathology, University of Kentucky, Lexington, KY 40546, USA
| | - Artemis D Treindl
- Institute of Integrative Biology, ETH Zurich, 8092 Zürich, Switzerland
| | | | | | - Adrian Leuchtmann
- Institute of Integrative Biology, ETH Zurich, 8092 Zürich, Switzerland
| | | | | | - Murray P Cox
- Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
| | | | - Barry Scott
- Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
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10
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Wang X, Reilly K, Heathcott R, Biswas A, Johnson LJ, Teasdale S, Grelet GA, Podolyan A, Gregorini P, Attwood GT, Palevich N, Morales SE. Soil Nitrogen Treatment Alters Microbiome Networks Across Farm Niches. Front Microbiol 2022; 12:786156. [PMID: 35237240 PMCID: PMC8882991 DOI: 10.3389/fmicb.2021.786156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 12/27/2021] [Indexed: 12/05/2022] Open
Abstract
Agriculture is fundamental for food production, and microbiomes support agriculture through multiple essential ecosystem services. Despite the importance of individual (i.e., niche specific) agricultural microbiomes, microbiome interactions across niches are not well-understood. To observe the linkages between nearby agricultural microbiomes, multiple approaches (16S, 18S, and ITS) were used to inspect a broad coverage of niche microbiomes. Here we examined agricultural microbiome responses to 3 different nitrogen treatments (0, 150, and 300 kg/ha/yr) in soil and tracked linked responses in other neighbouring farm niches (rumen, faecal, white clover leaf, white clover root, rye grass leaf, and rye grass root). Nitrogen treatment had little impact on microbiome structure or composition across niches, but drastically reduced the microbiome network connectivity in soil. Networks of 16S microbiomes were the most sensitive to nitrogen treatment across amplicons, where ITS microbiome networks were the least responsive. Nitrogen enrichment in soil altered soil and the neighbouring microbiome networks, supporting our hypotheses that nitrogen treatment in soil altered microbiomes in soil and in nearby niches. This suggested that agricultural microbiomes across farm niches are ecologically interactive. Therefore, knock-on effects on neighbouring niches should be considered when management is applied to a single agricultural niche.
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Affiliation(s)
- XinYue Wang
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Kerri Reilly
- AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand
| | - Rosemary Heathcott
- AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand
| | - Ambarish Biswas
- AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand
| | - Linda J. Johnson
- AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand
| | - Suliana Teasdale
- AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand
| | | | | | - Pablo Gregorini
- Department of Agricultural Science, Lincoln University, Lincoln, New Zealand
| | - Graeme T. Attwood
- AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand
| | - Nikola Palevich
- AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand
| | - Sergio E. Morales
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
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11
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Lukito Y, Lee K, Noorifar N, Green KA, Winter DJ, Ram A, Hale TK, Chujo T, Cox MP, Johnson LJ, Scott B. Regulation of host-infection ability in the grass-symbiotic fungus Epichloë festucae by histone H3K9 and H3K36 methyltransferases. Environ Microbiol 2020; 23:2116-2131. [PMID: 33350014 DOI: 10.1111/1462-2920.15370] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Revised: 12/02/2020] [Accepted: 12/19/2020] [Indexed: 01/30/2023]
Abstract
Recent studies have identified key genes that control the symbiotic interaction between Epichloë festucae and Lolium perenne. Here we report on the identification of specific E. festucae genes that control host infection. Deletion of setB, which encodes a homologue of the H3K36 histone methyltransferase Set2/KMT3, reduced histone H3K36 trimethylation and led to severe defects in colony growth and hyphal development. The E. festucae ΔclrD mutant, which lacks the gene encoding the homologue of the H3K9 methyltransferase KMT1, displays similar developmental defects. Both mutants are completely defective in their ability to infect L. perenne. Alleles that complement the culture and plant phenotypes of both mutants also complement the histone methylation defects. Co-inoculation of either ΔsetB or ΔclrD with the wild-type strain enables these mutants to colonize the host. However, successful colonization by the mutants resulted in death or stunting of the host plant. Transcriptome analysis at the early infection stage identified four fungal candidate genes, three of which encode small-secreted proteins, that are differentially regulated in these mutants compared to wild type. Deletion of crbA, which encodes a putative carbohydrate binding protein, resulted in significantly reduced host infection rates by E. festucae.
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Affiliation(s)
- Yonathan Lukito
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand.,AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand.,Bio-Protection Research Centre, Massey University, Palmerston North, New Zealand.,Ferrier Research Institute, Victoria University of Wellington, Wellington, New Zealand
| | - Kate Lee
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand.,Bio-Protection Research Centre, Massey University, Palmerston North, New Zealand
| | - Nazanin Noorifar
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Kimberly A Green
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - David J Winter
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Arvina Ram
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Tracy K Hale
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Tetsuya Chujo
- Research and Development Center, Mayekawa Mfg. Co., Ltd, Tokyo, Japan
| | - Murray P Cox
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand.,Bio-Protection Research Centre, Massey University, Palmerston North, New Zealand
| | - Linda J Johnson
- AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand
| | - Barry Scott
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand.,Bio-Protection Research Centre, Massey University, Palmerston North, New Zealand
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12
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Caradus JR, Johnson LJ. Epichloë Fungal Endophytes-From a Biological Curiosity in Wild Grasses to an Essential Component of Resilient High Performing Ryegrass and Fescue Pastures. J Fungi (Basel) 2020; 6:E322. [PMID: 33261217 PMCID: PMC7720123 DOI: 10.3390/jof6040322] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 11/13/2020] [Accepted: 11/18/2020] [Indexed: 12/15/2022] Open
Abstract
The relationship between Epichloë endophytes found in a wide range of temperate grasses spans the continuum from antagonistic to mutualistic. The diversity of asexual mutualistic types can be characterised by the types of alkaloids they produce in planta. Some of these are responsible for detrimental health and welfare issues of ruminants when consumed, while others protect the host plant from insect pests and pathogens. In many temperate regions they are an essential component of high producing resilient tall fescue and ryegrass swards. This obligate mutualism between fungus and host is a seed-borne technology that has resulted in several commercial products being used with high uptake rates by end-user farmers, particularly in New Zealand and to a lesser extent Australia and USA. However, this has not happened by chance. It has been reliant on multi-disciplinary research teams undertaking excellent science to understand the taxonomic relationships of these endophytes, their life cycle, symbiosis regulation at both the cellular and molecular level, and the impact of secondary metabolites, including an understanding of their mammalian toxicity and bioactivity against insects and pathogens. Additionally, agronomic trials and seed biology studies of these microbes have all contributed to the delivery of robust and efficacious products. The supply chain from science, through seed companies and retailers to the end-user farmer needs to be well resourced providing convincing information on the efficacy and ensuring effective quality control to result in a strong uptake of these Epichloë endophyte technologies in pastoral agriculture.
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Affiliation(s)
- John R. Caradus
- Grasslanz Technology Ltd., Palmerston North PB11008, New Zealand
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13
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Bastías DA, Johnson LJ, Card SD. Symbiotic bacteria of plant-associated fungi: friends or foes? Curr Opin Plant Biol 2020; 56:1-8. [PMID: 31786411 DOI: 10.1016/j.pbi.2019.10.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 10/21/2019] [Accepted: 10/30/2019] [Indexed: 06/10/2023]
Abstract
Many bacteria form symbiotic associations with plant-associated fungi. The effects of these symbionts on host fitness usually depend on symbiont or host genotypes and environmental conditions. However, bacterial endosymbionts, that is those living within fungal cells, may positively regulate host performance as their survival is often heavily dependent on host fitness. Contrary to this, bacteria that establish ectosymbiotic associations with fungi, that is those located on the hyphal surface or in close vicinity to fungal mycelia, may not have an apparent net effect on fungal performance due to the low level of fitness dependency on their host. Our analysis supports the hypothesis that endosymbiotic bacteria of fungi are beneficial symbionts, and that effects of ectosymbiotic bacteria on fungal performance depends on the bacterial type involved in the interaction (e.g. helper versus pathogen of fungi). Ecological scenarios, where the presence of beneficial bacterial endosymbionts of fungi could be compromised, are also discussed.
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Affiliation(s)
- Daniel A Bastías
- Forage Science, AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand.
| | - Linda J Johnson
- Forage Science, AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand
| | - Stuart D Card
- Forage Science, AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand
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14
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Forester NT, Lane GA, McKenzie CM, Lamont IL, Johnson LJ. The Role of SreA-Mediated Iron Regulation in Maintaining Epichloë festucae- Lolium perenne Symbioses. Mol Plant Microbe Interact 2019; 32:1324-1335. [PMID: 31107632 DOI: 10.1094/mpmi-03-19-0060-r] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In ascomycetes and basidiomycetes, iron-responsive GATA-type transcriptional repressors are involved in regulating iron homeostasis, notably to prevent iron toxicity through control of iron uptake. To date, it has been unknown whether this iron regulator contributes toward mutualistic endosymbiosis of microbes with plants, a system where the endophyte must function within the constraints of an in-host existence, including a dependency on the host for nutrient acquisition. Functional characterization of one such protein, SreA from Epichloë festucae, a fungal endosymbiont of cool-season grasses, indicates that regulation of iron homeostasis processes is important for symbiotic maintenance. The deletion of the sreA gene (ΔsreA) led to iron-dependent aberrant hyphal growth and the gradual loss of endophyte hyphae from perennial ryegrass. SreA negatively regulates the siderophore biosynthesis and high-affinity iron uptake systems of E. festucae, similar to other fungi, resulting in iron accumulation in mutants. Our evidence suggests that SreA is involved in the processes that moderate Epichloë iron acquisition from the plant apoplast, because overharvesting of iron in ΔsreA mutants was detected as premature chlorosis of the host using a hydroponic plant growth assay. E. festucae appears to have a tightly regulated iron management system, involving SreA that balances endophyte growth with its survival and prevents overcompetition with the host for iron in the intercellular niche, thus promoting mutualistic associations. Mutations that interfere with Epichloë iron management negatively affect iron-dependent fungal growth and destabilize mutualistic Epichloë -ryegrass associations.
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Affiliation(s)
- Natasha T Forester
- AgResearch Ltd., Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North 4442, New Zealand
| | - Geoffrey A Lane
- AgResearch Ltd., Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North 4442, New Zealand
| | - Catherine M McKenzie
- AgResearch Ltd., Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North 4442, New Zealand
| | - Iain L Lamont
- Department of Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | - Linda J Johnson
- AgResearch Ltd., Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North 4442, New Zealand
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15
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Lukito Y, Chujo T, Hale TK, Mace W, Johnson LJ, Scott B. Regulation of subtelomeric fungal secondary metabolite genes by H3K4me3 regulators CclA and KdmB. Mol Microbiol 2019; 112:837-853. [DOI: 10.1111/mmi.14320] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/30/2019] [Indexed: 11/28/2022]
Affiliation(s)
- Yonathan Lukito
- Institute of Fundamental Sciences Massey University Palmerston North New Zealand
- Grasslands Research Centre AgResearch Limited Palmerston North New Zealand
| | - Tetsuya Chujo
- Institute of Fundamental Sciences Massey University Palmerston North New Zealand
| | - Tracy K. Hale
- Institute of Fundamental Sciences Massey University Palmerston North New Zealand
| | - Wade Mace
- Grasslands Research Centre AgResearch Limited Palmerston North New Zealand
| | - Linda J. Johnson
- Grasslands Research Centre AgResearch Limited Palmerston North New Zealand
| | - Barry Scott
- Institute of Fundamental Sciences Massey University Palmerston North New Zealand
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16
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Campbell MA, Tapper BA, Simpson WR, Johnson RD, Mace W, Ram A, Lukito Y, Dupont PY, Johnson LJ, Scott DB, Ganley ARD, Cox MP. Epichloë hybrida, sp. nov., an emerging model system for investigating fungal allopolyploidy. Mycologia 2018; 109:715-729. [PMID: 29370579 DOI: 10.1080/00275514.2017.1406174] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Endophytes of the genus Epichloë (Clavicipitaceae, Ascomycota) frequently occur within cool-season grasses and form interactions with their hosts that range from mutualistic to antagonistic. Many Epichloë species have arisen via interspecific hybridization, resulting in species with two or three subgenomes that retain all or nearly all of their original parental genomes, a process termed allopolyploidization. Here, we characterize Epichloë hybrida, sp. nov., a mutualistic species that has increasingly become a model system for investigating allopolyploidy in fungi. The Epichloë species so far identified as the closest known relatives of the two progenitors of E. hybrida are E. festucae var. lolii and E. typhina. We confirm that the nuclear genome of E. hybrida contains two homeologs of most protein-coding genes from E. festucae and E. typhina, with genome-wide gene expression analysis indicating a slight bias in overall gene expression from the E. typhina subgenome. Mitochondrial DNA is detectable only from E. festucae, whereas ribosomal DNA is detectable only from E. typhina. Inheriting ribosomal DNA from just one parent might be expected to preferentially favor interactions with ribosomal proteins from the same parent, but we find that ribosomal protein genes from both parental subgenomes are nearly all expressed equally in E. hybrida. Finally, we provide a comprehensive set of resources for this model system that are intended to facilitate further study of fungal hybridization by other researchers.
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Affiliation(s)
- Matthew A Campbell
- a Institute of Fundamental Sciences, Massey University , Private Bag 11 222, Palmerston North 4410 , New Zealand
| | - Brian A Tapper
- b AgResearch Ltd., Grasslands Research Centre , Tennent Drive, Palmerston North 4442 , New Zealand
| | - Wayne R Simpson
- b AgResearch Ltd., Grasslands Research Centre , Tennent Drive, Palmerston North 4442 , New Zealand
| | - Richard D Johnson
- b AgResearch Ltd., Grasslands Research Centre , Tennent Drive, Palmerston North 4442 , New Zealand
| | - Wade Mace
- b AgResearch Ltd., Grasslands Research Centre , Tennent Drive, Palmerston North 4442 , New Zealand
| | - Arvina Ram
- a Institute of Fundamental Sciences, Massey University , Private Bag 11 222, Palmerston North 4410 , New Zealand
| | - Yonathan Lukito
- a Institute of Fundamental Sciences, Massey University , Private Bag 11 222, Palmerston North 4410 , New Zealand
| | - Pierre-Yves Dupont
- a Institute of Fundamental Sciences, Massey University , Private Bag 11 222, Palmerston North 4410 , New Zealand
| | - Linda J Johnson
- b AgResearch Ltd., Grasslands Research Centre , Tennent Drive, Palmerston North 4442 , New Zealand
| | - D Barry Scott
- a Institute of Fundamental Sciences, Massey University , Private Bag 11 222, Palmerston North 4410 , New Zealand
| | - Austen R D Ganley
- c School of Biological Sciences, University of Auckland , Private Bag 92019, Auckland 1142 , New Zealand
| | - Murray P Cox
- a Institute of Fundamental Sciences, Massey University , Private Bag 11 222, Palmerston North 4410 , New Zealand
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Gagic M, Faville MJ, Zhang W, Forester NT, Rolston MP, Johnson RD, Ganesh S, Koolaard JP, Easton HS, Hudson D, Johnson LJ, Moon CD, Voisey CR. Seed Transmission of Epichloë Endophytes in Lolium perenne Is Heavily Influenced by Host Genetics. Front Plant Sci 2018; 9:1580. [PMID: 30483280 PMCID: PMC6242978 DOI: 10.3389/fpls.2018.01580] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 10/10/2018] [Indexed: 05/14/2023]
Abstract
Vertical transmission of symbiotic Epichloë endophytes from host grasses into progeny seed is the primary mechanism by which the next generation of plants is colonized. This process is often imperfect, resulting in endophyte-free seedlings which may have poor ecological fitness if the endophyte confers protective benefits to its host. In this study, we investigated the influence of host genetics and environment on the vertical transmission of Epichloë festucae var. lolii strain AR37 in the temperate forage grass Lolium perenne. The efficiency of AR37 transmission into the seed of over 500 plant genotypes from five genetically diverse breeding populations was determined. In Populations I-III, which had undergone previous selection for high seed infection by AR37, mean transmission was 88, 93, and 92%, respectively. However, in Populations IV and V, which had not undergone previous selection, mean transmission was 69 and 70%, respectively. The transmission values, together with single-nucleotide polymorphism data obtained using genotyping-by-sequencing for each host, was used to develop a genomic prediction model for AR37 seed transmission. The predictive ability of the model was estimated at r = 0.54. While host genotype contributed greatly to differences in AR37 seed transmission, undefined environmental variables also contributed significantly to seed transmission across different years and geographic locations. There was evidence for a small host genotype-by-environment effect; however this was less pronounced than genotype or environment alone. Analysis of endophyte infection levels in parent plants within Populations I and IV revealed a loss of endophyte infection over time in Population IV only. This population also had lower average tiller infection frequencies than Population I, suggesting that AR37 failed to colonize all the daughter tillers and therefore seeds. However, we also observed that infection of seed by AR37 may fail during or after initiation of floral development from plants where all tillers remained endophyte-infected over time. While the effects of environment and host genotype on fungal endophyte transmission have been evaluated previously, this is the first study that quantifies the relative impacts of host genetics and environment on endophyte vertical transmission.
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Affiliation(s)
- Milan Gagic
- AgResearch, Grasslands Research Centre, Palmerston North, New Zealand
| | - Marty J. Faville
- AgResearch, Grasslands Research Centre, Palmerston North, New Zealand
| | - Wei Zhang
- AgResearch, Grasslands Research Centre, Palmerston North, New Zealand
| | | | | | | | - Siva Ganesh
- AgResearch, Grasslands Research Centre, Palmerston North, New Zealand
| | - John P. Koolaard
- AgResearch, Grasslands Research Centre, Palmerston North, New Zealand
| | - H. Sydney Easton
- AgResearch, Grasslands Research Centre, Palmerston North, New Zealand
| | - Debbie Hudson
- AgResearch, Grasslands Research Centre, Palmerston North, New Zealand
| | - Linda J. Johnson
- AgResearch, Grasslands Research Centre, Palmerston North, New Zealand
| | - Christina D. Moon
- AgResearch, Grasslands Research Centre, Palmerston North, New Zealand
| | - Christine R. Voisey
- AgResearch, Grasslands Research Centre, Palmerston North, New Zealand
- *Correspondence: Christine R. Voisey,
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18
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Voisey CR, Christensen MT, Johnson LJ, Forester NT, Gagic M, Bryan GT, Simpson WR, Fleetwood DJ, Card SD, Koolaard JP, Maclean PH, Johnson RD. cAMP Signaling Regulates Synchronised Growth of Symbiotic Epichloë Fungi with the Host Grass Lolium perenne. Front Plant Sci 2016; 7:1546. [PMID: 27833620 PMCID: PMC5082231 DOI: 10.3389/fpls.2016.01546] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 10/03/2016] [Indexed: 05/04/2023]
Abstract
The seed-transmitted fungal symbiont, Epichloë festucae, colonizes grasses by infecting host tissues as they form on the shoot apical meristem (SAM) of the seedling. How this fungus accommodates the complexities of plant development to successfully colonize the leaves and inflorescences is unclear. Since adenosine 3', 5'-cyclic monophosphate (cAMP)-dependent signaling is often essential for host colonization by fungal pathogens, we disrupted the cAMP cascade by insertional mutagenesis of the E. festucae adenylate cyclase gene (acyA). Consistent with deletions of this gene in other fungi, acyA mutants had a slow radial growth rate in culture, and hyphae were convoluted and hyper-branched suggesting that fungal apical dominance had been disrupted. Nitro blue tetrazolium (NBT) staining of hyphae showed that cAMP disruption mutants were impaired in their ability to synthesize superoxide, indicating that cAMP signaling regulates accumulation of reactive oxygen species (ROS). Despite significant defects in hyphal growth and ROS production, E. festucae ΔacyA mutants were infectious and capable of forming symbiotic associations with grasses. Plants infected with E. festucae ΔacyA were marginally less robust than the wild-type (WT), however hyphae were hyper-branched, and leaf tissues heavily colonized, indicating that the tight regulation of hyphal growth normally observed in maturing leaves requires functional cAMP signaling.
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Affiliation(s)
- Christine R. Voisey
- Forage Science, AgResearch Ltd., Grasslands Research CentrePalmerston North, New Zealand
| | - Michael T. Christensen
- Formally of Forage Improvement, AgResearch Ltd., Grasslands Research CentrePalmerston North, New Zealand
| | - Linda J. Johnson
- Forage Science, AgResearch Ltd., Grasslands Research CentrePalmerston North, New Zealand
| | - Natasha T. Forester
- Forage Science, AgResearch Ltd., Grasslands Research CentrePalmerston North, New Zealand
| | - Milan Gagic
- Forage Science, AgResearch Ltd., Grasslands Research CentrePalmerston North, New Zealand
| | - Gregory T. Bryan
- Forage Science, AgResearch Ltd., Grasslands Research CentrePalmerston North, New Zealand
| | - Wayne R. Simpson
- Forage Science, AgResearch Ltd., Grasslands Research CentrePalmerston North, New Zealand
| | - Damien J. Fleetwood
- Biotelliga Ltd., Institute for Innovation in BiotechnologyAuckland, New Zealand
| | - Stuart D. Card
- Forage Science, AgResearch Ltd., Grasslands Research CentrePalmerston North, New Zealand
| | - John P. Koolaard
- Bioinformatics and Statistics Team, AgResearch Ltd., Grasslands Research CentrePalmerston North, New Zealand
| | - Paul H. Maclean
- Bioinformatics and Statistics Team, AgResearch Ltd., Lincoln Research CentreChristchurch, New Zealand
| | - Richard D. Johnson
- Forage Science, AgResearch Ltd., Grasslands Research CentrePalmerston North, New Zealand
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19
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Abstract
This minireview highlights the importance of endophytic fungi for sustainable agriculture and horticulture production. Fungal endophytes play a key role in habitat adaptation of plants resulting in improved plant performance and plant protection against biotic and abiotic stresses. They encode a vast variety of novel secondary metabolites including volatile organic compounds. In addition to protecting plants against pathogens and pests, selected fungal endophytes have been used to remove animal toxicities associated with fungal endophytes in temperate grasses, to create corn and rice plants that are tolerant to a range of biotic and abiotic stresses, and for improved management of post-harvest control. We argue that practices used in plant breeding, seed treatments and agriculture, often caused by poor knowledge of the importance of fungal endophytes, are among the reasons for the loss of fungal endophyte diversity in domesticated plants and also accounts for the reduced effectiveness of some endophyte strains to confer plant benefits. We provide recommendations on how to mitigate against these negative impacts in modern agriculture.
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Affiliation(s)
- Ben J J Lugtenberg
- Institute of Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, the Netherlands
| | - John R Caradus
- Grasslanz Technology Limited, PB 11008, Palmerston North, 4442, New Zealand
| | - Linda J Johnson
- Forage Science, AgResearch Limited, PB 11008, Palmerston North, 4442, New Zealand
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20
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Sim SL, Szalewski RJ, Johnson LJ, Akah LE, Shoemaker LE, Thoreson WB, Margalit E. Simultaneous recording of mouse retinal ganglion cells during epiretinal or subretinal stimulation. Vision Res 2014; 101:41-50. [PMID: 24863584 DOI: 10.1016/j.visres.2014.05.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 04/28/2014] [Accepted: 05/12/2014] [Indexed: 10/25/2022]
Abstract
We compared response patterns and electrical receptive fields (ERF) of retinal ganglion cells (RGCs) during epiretinal and subretinal electrical stimulation of isolated mouse retina. Retinas were stimulated with an array of 3200 independently controllable electrodes. Four response patterns were observed: a burst of activity immediately after stimulation (Type I cells, Vision Research (2008), 48, 1562-1568), delayed bursts beginning >25ms after stimulation (Type II), a combination of both (Type III), and inhibition of ongoing spike activity. Type I responses were produced more often by epiretinal than subretinal stimulation whereas delayed and inhibitory responses were evoked more frequently by subretinal stimulation. Response latencies were significantly shorter with epiretinal than subretinal stimulation. These data suggest that subretinal stimulation is more effective at activating intraretinal circuits than epiretinal stimulation. There was no significant difference in charge threshold between subretinal and epiretinal configurations. ERFs were defined by the stimulating array surface area that successfully stimulated spikes in an RGC. ERFs were complex in shape, similar to receptive fields mapped with light. ERF areas were significantly smaller with subretinal than epiretinal stimulation. This may reflect the greater distance between stimulating electrodes and RGCs in the subretinal configuration. ERFs for immediate and delayed responses mapped within the same Type III cells differed in shape and size, consistent with different sites and mechanisms for generating these two response types.
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Affiliation(s)
- S L Sim
- Department of Ophthalmology and Visual Science, University of Nebraska Medical Center, Omaha, NE, USA
| | - R J Szalewski
- Department of Ophthalmology and Visual Science, University of Nebraska Medical Center, Omaha, NE, USA
| | - L J Johnson
- Naval Research Laboratory, Washington, DC, USA
| | - L E Akah
- Department of Ophthalmology and Visual Science, University of Nebraska Medical Center, Omaha, NE, USA
| | - L E Shoemaker
- Department of Ophthalmology and Visual Science, University of Nebraska Medical Center, Omaha, NE, USA
| | - W B Thoreson
- Department of Ophthalmology and Visual Science, University of Nebraska Medical Center, Omaha, NE, USA; Department of Pharmacology and Experimental Neuroscience, University of Nebraska, NE, USA
| | - E Margalit
- VA Nebraska-Western Iowa Health Care System, NE, USA; Department of Ophthalmology and Visual Science, University of Nebraska Medical Center, Omaha, NE, USA.
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Johnson LJ, Koulman A, Christensen M, Lane GA, Fraser K, Forester N, Johnson RD, Bryan GT, Rasmussen S. An extracellular siderophore is required to maintain the mutualistic interaction of Epichloë festucae with Lolium perenne. PLoS Pathog 2013; 9:e1003332. [PMID: 23658520 PMCID: PMC3642064 DOI: 10.1371/journal.ppat.1003332] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2012] [Accepted: 03/15/2013] [Indexed: 11/19/2022] Open
Abstract
We have identified from the mutualistic grass endophyte Epichloë festucae a non-ribosomal peptide synthetase gene (sidN) encoding a siderophore synthetase. The enzymatic product of SidN is shown to be a novel extracellular siderophore designated as epichloënin A, related to ferrirubin from the ferrichrome family. Targeted gene disruption of sidN eliminated biosynthesis of epichloënin A in vitro and in planta. During iron-depleted axenic growth, ΔsidN mutants accumulated the pathway intermediate N(5)-trans-anhydromevalonyl-N(5)-hydroxyornithine (trans-AMHO), displayed sensitivity to oxidative stress and showed deficiencies in both polarized hyphal growth and sporulation. Infection of Lolium perenne (perennial ryegrass) with ΔsidN mutants resulted in perturbations of the endophyte-grass symbioses. Deviations from the characteristic tightly regulated synchronous growth of the fungus with its plant partner were observed and infected plants were stunted. Analysis of these plants by light and transmission electron microscopy revealed abnormalities in the distribution and localization of ΔsidN mutant hyphae as well as deformities in hyphal ultrastructure. We hypothesize that lack of epichloënin A alters iron homeostasis of the symbiotum, changing it from mutually beneficial to antagonistic. Iron itself or epichloënin A may serve as an important molecular/cellular signal for controlling fungal growth and hence the symbiotic interaction.
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Affiliation(s)
- Linda J Johnson
- AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand.
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22
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Mader TL, Gaughan JB, Johnson LJ, Hahn GL. Tympanic temperature in confined beef cattle exposed to excessive heat load. Int J Biometeorol 2010; 54:629-635. [PMID: 19404683 DOI: 10.1007/s00484-009-0229-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Revised: 03/26/2009] [Accepted: 04/06/2009] [Indexed: 05/27/2023]
Abstract
Angus crossbred yearling steers (n = 168) were used to evaluate effects on performance and tympanic temperature (TT) of feeding additional potassium and sodium to steers exposed to excessive heat load (maximum daily ambient temperature exceeded 32°C for three consecutive days) during seasonal summer conditions. Steers were assigned one of four treatments: (1) control; (2) potassium supplemented (diet containing 2.10% KHCO₃); (3) sodium supplemented (diet containing 1.10% NaCl); or (4) potassium and sodium supplemented (diet containing 2.10% KHCO₃ and 1.10% NaCl). Overall, additional KHCO₃ at the 2% level or NaCl at the 1% level did not improve performance or heat stress tolerance with these diet formulations. However, the addition of KHCO₃ did enhance water intake. Independent of treatment effects, TT of cattle displaying high, moderate, or low levels of stress suggest that cattle that do not adequately cool down at night are prone to achieving greater body temperatures during a subsequent hot day. Cattle that are prone to get hot but can cool at night can keep average tympanic temperatures at or near those of cattle that tend to consistently maintain lower peak and mean body temperatures. In addition, during cooler and moderately hot periods, cattle change TT in a stair-step or incremental pattern, while under hot conditions, average TT of group-fed cattle moves in conjunction with ambient conditions, indicating that thermoregulatory mechanisms are at or near maximum physiological capacity.
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Affiliation(s)
- T L Mader
- Haskell Agricultural Laboratory, Department of Animal Science, University of Nebraska, 57905 866 Road, Concord, NE 68728, USA.
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23
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Abstract
Alterations to the genetic code--codon reassignments--have occurred many times in life's history, despite the fact that genomes are coadapted to their genetic codes and therefore alterations are likely to be maladaptive. A potential mechanism for adaptive codon reassignment, which could trigger either a temporary period of codon ambiguity or a permanent genetic code change, is the reactivation of a pseudogene by a nonsense suppressor mutant transfer RNA. I examine the population genetics of each stage of this process and find that pseudogene rescue is plausible and also readily explains some features of extant variability in genetic codes.
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Affiliation(s)
- L J Johnson
- School of Biological Sciences, University of Reading, Reading, UK.
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24
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Abstract
Epigenetics has progressed rapidly from an obscure quirk of heredity into a data-heavy 'omic' science. Our understanding of the molecular mechanisms of epigenomic regulation, and the extent of its importance in nature, are far from complete, but in spite of such drawbacks, population-level studies are extremely valuable: epigenomic regulation is involved in several processes central to evolutionary biology including phenotypic plasticity, evolvability and the mediation of intragenomic conflicts. The first studies of epigenomic variation within populations suggest high levels of phenotypically relevant variation, with the patterns of epigenetic regulation varying between individuals and genome regions as well as with environment. Epigenetic mechanisms appear to function primarily as genome defences, but result in the maintenance of plasticity together with a degree of buffering of developmental programmes; periodic breakdown of epigenetic buffering could potentially cause variation in rates of phenotypic evolution.
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Affiliation(s)
- L J Johnson
- School of Biological Sciences, University of Reading, Reading, UK.
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25
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Lee TV, Johnson LJ, Johnson RD, Koulman A, Lane GA, Lott JS, Arcus VL. Structure of a eukaryotic nonribosomal peptide synthetase adenylation domain that activates a large hydroxamate amino acid in siderophore biosynthesis. J Biol Chem 2009; 285:2415-27. [PMID: 19923209 DOI: 10.1074/jbc.m109.071324] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Nonribosomal peptide synthetases (NRPSs) are large, multidomain proteins that are involved in the biosynthesis of an array of secondary metabolites. We report the structure of the third adenylation domain from the siderophore-synthesizing NRPS, SidN, from the endophytic fungus Neotyphodium lolii. This is the first structure of a eukaryotic NRPS domain, and it reveals a large binding pocket required to accommodate the unusual amino acid substrate, N(delta)-cis-anhydromevalonyl-N(delta)-hydroxy-L-ornithine (cis-AMHO). The specific activation of cis-AMHO was confirmed biochemically, and an AMHO moiety was unambiguously identified as a component of the fungal siderophore using mass spectroscopy. The protein structure shows that the substrate binding pocket is defined by 17 amino acid residues, in contrast to both prokaryotic adenylation domains and to previous predictions based on modeling. Existing substrate prediction methods for NRPS adenylation domains fail for domains from eukaryotes due to the divergence of their signature sequences from those of prokaryotes. Thus, this new structure will provide a basis for improving prediction methods for eukaryotic NRPS enzymes that play important and diverse roles in the biology of fungi.
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Affiliation(s)
- T Verne Lee
- AgResearch Structural Biology Laboratory, School of Biological Sciences, University of Auckland, Auckland 1142, New Zealand
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Rubio JP, Stankovich J, Field J, Tubridy N, Marriott M, Chapman C, Bahlo M, Perera D, Johnson LJ, Tait BD, Varney MD, Speed TP, Taylor BV, Foote SJ, Butzkueven H, Kilpatrick TJ. Replication of KIAA0350, IL2RA, RPL5 and CD58 as multiple sclerosis susceptibility genes in Australians. Genes Immun 2008; 9:624-30. [PMID: 18650830 DOI: 10.1038/gene.2008.59] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A recent genome-wide association study (GWAS) conducted by the International Multiple Sclerosis Genetics Consortium (IMSGC) identified a number of putative MS susceptibility genes. Here we have performed a replication study in 1134 Australian MS cases and 1265 controls for 17 risk-associated single nucleotide polymorphisms (SNPs) reported by the IMSGC. Of 16 SNPs that passed quality control filters, four, each corresponding to a different non-human leukocyte antigen (HLA) gene, were associated with disease susceptibility: KIAA0350 (rs6498169) P=0.001, IL2RA (rs2104286) P=0.033, RPL5 (rs6604026) P=0.041 and CD58 (rs12044852) P=0.042. There was no association (P=0.58) between rs6897932 in the IL7R gene and the risk of MS. No interactions were detected between the replicated IMSGC SNPs and HLA-DRB1*15, gender, disease course, disease progression or age-at-onset. We used a novel Bayesian approach to estimate the extent to which our data increased or decreased evidence for association with the six most-associated IMSGC loci. These analyses indicated that even modest P-values, such as those reported here, can contribute markedly to the posterior probability of 'true' association in replication studies. In conclusion, these data provide support for the involvement of four non-HLA genes in the pathogenesis of MS, and combined with previous data, increase to genome-wide significance (P=3 x 10(-8)) evidence of an association between KIAA0350 and risk of disease.
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Affiliation(s)
- J P Rubio
- The Howard Florey Institute, Melbourne, Victoria, Australia.
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Cao M, Koulman A, Johnson LJ, Lane GA, Rasmussen S. Advanced data-mining strategies for the analysis of direct-infusion ion trap mass spectrometry data from the association of perennial ryegrass with its endophytic fungus, Neotyphodium lolii. Plant Physiol 2008; 146:1501-14. [PMID: 18287492 PMCID: PMC2287329 DOI: 10.1104/pp.107.112458] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2007] [Accepted: 02/18/2008] [Indexed: 05/22/2023]
Abstract
Direct-infusion mass spectrometry (MS) was applied to study the metabolic effects of the symbiosis between the endophytic fungus Neotyphodium lolii and its host perennial ryegrass (Lolium perenne) in three different tissues (immature leaf, blade, and sheath). Unbiased direct-infusion MS using a linear ion trap mass spectrometer allowed metabolic effects to be determined free of any preconceptions and in a high-throughput fashion. Not only the full MS(1) mass spectra (range 150-1,000 mass-to-charge ratio) were obtained but also MS(2) and MS(3) product ion spectra were collected on the most intense MS(1) ions as described previously (Koulman et al., 2007b). We developed a novel computational methodology to take advantage of the MS(2) product ion spectra collected. Several heterogeneous MS(1) bins (different MS(2) spectra from the same nominal MS(1)) were identified with this method. Exploratory data analysis approaches were also developed to investigate how the metabolome differs in perennial ryegrass infected with N. lolii in comparison to uninfected perennial ryegrass. As well as some known fungal metabolites like peramine and mannitol, several novel metabolites involved in the symbiosis, including putative cyclic oligopeptides, were identified. Correlation network analysis revealed a group of structurally related oligosaccharides, which differed significantly in concentration in perennial ryegrass sheaths due to endophyte infection. This study demonstrates the potential of the combination of unbiased metabolite profiling using ion trap MS and advanced data-mining strategies for discovering unexpected perturbations of the metabolome, and generating new scientific questions for more detailed investigations in the future.
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Affiliation(s)
- Mingshu Cao
- AgResearch Limited, Grasslands Research Centre, Palmerston North 4442, New Zealand
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Burfoot RK, Jensen CJ, Field J, Stankovich J, Varney MD, Johnson LJ, Butzkueven H, Booth D, Bahlo M, Tait BD, Taylor BV, Speed TP, Heard R, Stewart GJ, Foote SJ, Kilpatrick TJ, Rubio JP. SNP mapping and candidate gene sequencing in the class I region of the HLA complex: searching for multiple sclerosis susceptibility genes in Tasmanians. ACTA ACUST UNITED AC 2007; 71:42-50. [PMID: 17971048 DOI: 10.1111/j.1399-0039.2007.00962.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This study is an extension to previously published work that has linked variation in the human leukocyte antigen (HLA) class I region with susceptibility to multiple sclerosis (MS) in Australians from the Island State of Tasmania. Single nucleotide polymorphism (SNP) mapping was performed on an 865-kb candidate region (D6S1683-D6S265) in 166 Tasmanian MS families, and seven candidate genes [ubiquitin D (UBD), olfactory receptor 2H3 (OR2H3), gamma-aminobutyric acid B receptor 1 (GABBR1), myelin oligodendrocyte glycoprotein (MOG), HLA-F, HLA complex group 4 (HCG4) and HLA-G] were resequenced. SNPs tagging the extended MS susceptibility haplotype were genotyped in an independent sample of 356 Australian MS trios and SNPs in the MOG gene were significantly over-transmitted to MS cases. We identified significant effects on MS susceptibility of HLA-A*2 (OR: 0.51; P = 0.05) and A*3 (OR: 2.85; P = 0.005), and two coding polymorphisms in the MOG gene (V145I: P = 0.01, OR: 2.2; V142L: P = 0.04, OR: 0.45) after full conditioning on HLA-DRB1. We have therefore identified plausible candidates for the causal MS susceptibility allele, and although not conclusive at this stage, our data provide suggestive evidence for multiple class I MS susceptibility genes.
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Affiliation(s)
- R K Burfoot
- Howard Florey Institute, University of Melbourne, Melbourne, Victoria, Australia
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Rasmussen S, Parsons AJ, Bassett S, Christensen MJ, Hume DE, Johnson LJ, Johnson RD, Simpson WR, Stacke C, Voisey CR, Xue H, Newman JA. High nitrogen supply and carbohydrate content reduce fungal endophyte and alkaloid concentration in Lolium perenne. New Phytol 2007; 173:787-797. [PMID: 17286827 DOI: 10.1111/j.1469-8137.2006.01960.x] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The relationship between cool-season grasses and fungal endophytes is widely regarded as mutualistic, but there is growing uncertainty about whether changes in resource supply and environment benefit both organisms to a similar extent. Here, we infected two perennial ryegrass (Lolium perenne) cultivars (AberDove, Fennema) that differ in carbohydrate content with three strains of Neotyphodium lolii (AR1, AR37, common strain) that differ intrinsically in alkaloid profile. We grew endophyte-free and infected plants under high and low nitrogen (N) supply and used quantitative PCR (qPCR) to estimate endophyte concentrations in harvested leaf tissues. Endophyte concentration was reduced by 40% under high N supply, and by 50% in the higher sugar cultivar. These two effects were additive (together resulting in 75% reduction). Alkaloid production was also reduced under both increased N supply and high sugar cultivar, and for three of the four alkaloids quantified, concentrations were linearly related to endophyte concentration. The results stress the need for wider quantification of fungal endophytes in the grassland-foliar endophyte context, and have implications for how introducing new cultivars, novel endophytes or increasing N inputs affect the role of endophytes in grassland ecosystems.
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Affiliation(s)
| | | | | | | | - David E Hume
- AgResearch, P.B. 11008, Palmerston North, New Zealand
| | | | | | | | | | | | - Hong Xue
- AgResearch, P.B. 11008, Palmerston North, New Zealand
| | - Jonathan A Newman
- Department of Environmental Biology, University of Guelph, Ontario, Canada N1G 2W1
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Lee MA, Weachter R, Pollak S, Kremers MS, Naik AM, Silverman R, Tuzi J, Wang W, Johnson LJ, Euler DE. The effect of atrial pacing therapies on atrial tachyarrhythmia burden and frequency: results of a randomized trial in patients with bradycardia and atrial tachyarrhythmias. J Am Coll Cardiol 2003; 41:1926-32. [PMID: 12798559 DOI: 10.1016/s0735-1097(03)00426-1] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
OBJECTIVES The Atrial Therapy Efficacy and Safety Trial (ATTEST) was a prospective, randomized study to evaluate preventive pacing and antitachycardia pacing (ATP) in patients with symptomatic atrial fibrillation (AF) or atrial tachycardia (AT). BACKGROUND The effect of the combination of atrial prevention and termination algorithms on AT/AF burden and frequency in pacemaker patients is unknown. METHODS A DDDRP pacemaker (AT500, Medtronic Inc., Minneapolis, Minnesota) with three atrial preventive pacing algorithms and two ATP algorithms was implanted in 368 patients. Patients were randomized one-month post-implant to all prevention and ATP therapies ON or OFF and followed for three months. The OFF group had DDDR pacing at a lower programmed rate of 60 ppm. The AT/AF burden and frequency were determined from daily device counters in 324 patients treated according to protocol. RESULTS In 17,018 episodes with stored electrograms, appropriate detection was confirmed in 17,004 (99.9%). The median percentage of atrial pacing was 98% in the ON group versus 75% in the OFF group (p < 0.001). Using device-defined criteria for successful termination, ATP terminated 8,590 (54%) of 15,789 treated episodes. The median AT/AF burden during the three-month study period was 4.2 h/month ON versus 1.1 h/month OFF (p = 0.20). The median AT/AF frequency was 1.3 episodes/month ON versus 1.2 episodes/month OFF (p = 0.65). System-related, complication-free survival at four months was 90.2% (Kaplan-Meier estimate). CONCLUSIONS This DDDRP pacemaker is safe, has accurate AT/AF detection, and provides ATP with 54% efficacy as defined by the device. The atrial prevention and termination therapies combined did not reduce AT/AF burden or frequency in this patient population.
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Affiliation(s)
- Michael A Lee
- John Muir/Mount Diablo Medical Center, Walnut Creek, California, USA.
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Johnson LJ. Testifying at a deposition. Med Econ 2001; 78:53. [PMID: 11808472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
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Johnson LJ. "Sick" notes for patients. Med Econ 2001; 78:82. [PMID: 11808043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
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Johnson LJ. A department head's liability for a colleague's mishap. Med Econ 2001; 78:84. [PMID: 11762119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
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Johnson LJ. Malpractice consult. When a patient gets an "executive physical". Med Econ 2001; 78:68, 71. [PMID: 11715375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
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Johnson LJ. Your liability when you recommend a private duty nurse. MEDICAL ECONOMICS 2001; 78:96. [PMID: 11682889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
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Johnson LJ. Paying for your partners' mistakes. Med Econ 2001; 78:98. [PMID: 11601174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
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Johnson LJ. Physician liability and drug recalls. Med Econ 2001; 78:118. [PMID: 11573390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
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Johnson LJ. Off-label prescribing and the standard of care. Med Econ 2001; 78:97. [PMID: 11550443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
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Johnson LJ. Liability insurance for a physician assistant. Med Econ 2001; 78:116. [PMID: 11521487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
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Johnson LJ, Johnson RD, Akamatsu H, Salamiah A, Otani H, Kohmoto K, Kodama M. Spontaneous loss of a conditionally dispensable chromosome from the Alternaria alternata apple pathotype leads to loss of toxin production and pathogenicity. Curr Genet 2001; 40:65-72. [PMID: 11570518 DOI: 10.1007/s002940100233] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The Alternaria alternata apple pathotype causes Alternaria blotch of susceptible apple cultivars through the production of a cyclic peptide, host-specific toxin, AM-toxin. We recently cloned a cyclic peptide synthetase gene, AMT, whose product catalyzes the production of AM-toxin and showed that it resides on chromosomes of 1.8 Mb or less, depending on the A. alternata apple pathotype strain. Reverse transcriptase (RT)-PCR, using primers specific to AMT, on laboratory sub-cultured strains previously shown to produce AM-toxin, identified one isolate that did not express the gene. A leaf necrosis bioassay confirmed an AM-toxin-minus phenotype. However, an original isolate of this strain which had not undergone sub-culture gave a positive result by both RTPCR and bioassay. Contour-clamped homogeneous electric field electrophoresis and Southern hybridization demonstrated the loss of a 1.1-Mb chromosome in the non-toxin-producing isolate. Since this chromosome can be entirely lost without affecting growth, but is necessary for pathogenicity, we propose it is a conditionally dispensable chromosome.
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Affiliation(s)
- L J Johnson
- Laboratory of Plant Pathology, Faculty of Agriculture, Tottori University, Japan
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Johnson LJ. Statutes of limitations may offer a lot less protection. Med Econ 2001; 78:93. [PMID: 11499294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
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Johnson LJ. Your obligations when doing pre-employment exams. Med Econ 2001; 78:146. [PMID: 11478172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
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Johnson LJ. Are rural doctors held to big-city standards? Med Econ 2001; 78:101. [PMID: 11471416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
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Johnson LJ. No follow-up for indigent patients? Med Econ 2001; 78:105. [PMID: 11436717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
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Johnson LJ. When it's wise to hire your own attorney. Med Econ 2001; 78:118, 121. [PMID: 11409264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
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Johnson LJ. How to avoid medication errors. Med Econ 2001; 78:137. [PMID: 11386069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
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Johnson LJ. When a patient might become violent. Med Econ 2001; 78:125. [PMID: 11338237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/16/2023]
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Johnson LJ. Your obligation to treat patients referred by the ER. Med Econ 2001; 78:93. [PMID: 11277011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
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Johnson LJ. Domestic violence and physician liability. Med Econ 2001; 78:119. [PMID: 11252429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
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50
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Johnson LJ. When bad news might make patients sicker. Med Econ 2001; 78:114. [PMID: 11218940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
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