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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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Guo Y, Hunziker L, Mesarich CH, Chettri P, Dupont PY, Ganley RJ, McDougal RL, Barnes I, Bradshaw RE. DsEcp2-1 is a polymorphic effector that restricts growth of Dothistroma septosporum in pine. Fungal Genet Biol 2020; 135:103300. [PMID: 31730909 DOI: 10.1016/j.fgb.2019.103300] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Revised: 11/05/2019] [Accepted: 11/05/2019] [Indexed: 12/22/2022]
Abstract
The detrimental effect of fungal pathogens on forest trees is an increasingly important problem that has implications for the health of our planet. Despite this, the study of molecular plant-microbe interactions in forest trees is in its infancy, and very little is known about the roles of effector molecules from forest pathogens. Dothistroma septosporum causes a devastating needle blight disease of pines, and intriguingly, is closely related to Cladosporium fulvum, a tomato pathogen in which pioneering effector biology studies have been carried out. Here, we studied D. septosporum effectors that are shared with C. fulvum, by comparing gene sequences from global isolates of D. septosporum and assessing effector function in both host and non-host plants. Many of the effectors were predicted to be non-functional in D. septosporum due to their pseudogenization or low expression in planta, suggesting adaptation to lifestyle and host. Effector sequences were polymorphic among a global collection of D. septosporum isolates, but there was no evidence for positive selection. The DsEcp2-1 effector elicited cell death in the non-host plant Nicotiana tabacum, whilst D. septosporum DsEcp2-1 mutants showed increased colonization of pine needles. Together these results suggest that DsEcp2-1 might be recognized by an immune receptor in both angiosperm and gymnosperm plants. This work may lead to the identification of plant targets for DsEcp2-1 that will provide much needed information on the molecular basis of gymnosperm-pathogen interactions in forests, and may also lead to novel methods of disease control.
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Affiliation(s)
- Yanan Guo
- Bio-Protection Research Centre, School of Fundamental Sciences, Massey University, Palmerston North 4474, New Zealand.
| | - Lukas Hunziker
- Bio-Protection Research Centre, School of Fundamental Sciences, Massey University, Palmerston North 4474, New Zealand
| | - Carl H Mesarich
- Bio-Protection Research Centre, School of Agriculture and Environment, Massey University, Palmerston North 4474, New Zealand
| | - Pranav Chettri
- AgResearch Ltd, Grasslands Research Centre, Palmerston North, New Zealand
| | - Pierre-Yves Dupont
- Institute of Environmental Science and Research, Christchurch 8041, New Zealand
| | - Rebecca J Ganley
- The New Zealand Institute for Plant & Food Research Limited, Te Puke, New Zealand
| | - Rebecca L McDougal
- Scion, New Zealand Forest Research Institute Ltd, Rotorua 3010, New Zealand
| | - Irene Barnes
- Department of Genetics, Biochemistry and Microbiology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa
| | - Rosie E Bradshaw
- Bio-Protection Research Centre, School of Fundamental Sciences, Massey University, Palmerston North 4474, New Zealand
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Bradshaw RE, Sim AD, Chettri P, Dupont P, Guo Y, Hunziker L, McDougal RL, Van der Nest A, Fourie A, Wheeler D, Cox MP, Barnes I. Global population genomics of the forest pathogen Dothistroma septosporum reveal chromosome duplications in high dothistromin-producing strains. Mol Plant Pathol 2019; 20:784-799. [PMID: 30938073 PMCID: PMC6637865 DOI: 10.1111/mpp.12791] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Dothistroma needle blight is one of the most devastating pine tree diseases worldwide. New and emerging epidemics have been frequent over the last 25 years, particularly in the Northern Hemisphere, where they are in part associated with changing weather patterns. One of the main Dothistroma needle blight pathogens, Dothistroma septosporum, has a global distribution but most molecular plant pathology research has been confined to Southern Hemisphere populations that have limited genetic diversity. Extensive genomic and transcriptomic data are available for a D. septosporum reference strain from New Zealand, where an introduced clonal population of the pathogen predominates. Due to the global importance of this pathogen, we determined whether the genome of this reference strain is representative of the species worldwide by sequencing the genomes of 18 strains sampled globally from different pine hosts. Genomic polymorphism shows substantial variation within the species, clustered into two distinct groups of strains with centres of diversity in Central and South America. A reciprocal chromosome translocation uniquely identifies the New Zealand strains. Globally, strains differ in their production of the virulence factor dothistromin, with extremely high production levels in strain ALP3 from Germany. Comparisons with the New Zealand reference revealed that several strains are aneuploids; for example, ALP3 has duplications of three chromosomes. Increased gene copy numbers therefore appear to contribute to increased production of dothistromin, emphasizing that studies of population structure are a necessary adjunct to functional analyses of genetic polymorphisms to identify the molecular basis of virulence in this important forest pathogen.
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Affiliation(s)
- Rosie E. Bradshaw
- School of Fundamental Sciences and Bio‐Protection Research CentreMassey UniversityPalmerston North4410New Zealand
| | - Andre D. Sim
- School of Fundamental Sciences and Bio‐Protection Research CentreMassey UniversityPalmerston North4410New Zealand
| | - Pranav Chettri
- School of Fundamental Sciences and Bio‐Protection Research CentreMassey UniversityPalmerston North4410New Zealand
| | - Pierre‐Yves Dupont
- School of Fundamental Sciences and Bio‐Protection Research CentreMassey UniversityPalmerston North4410New Zealand
- Institute of Environmental Science and ResearchChristchurch8041New Zealand
| | - Yanan Guo
- School of Fundamental Sciences and Bio‐Protection Research CentreMassey UniversityPalmerston North4410New Zealand
| | - Lukas Hunziker
- School of Fundamental Sciences and Bio‐Protection Research CentreMassey UniversityPalmerston North4410New Zealand
| | | | - Ariska Van der Nest
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI)University of PretoriaPretoriaSouth Africa
| | - Arista Fourie
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI)University of PretoriaPretoriaSouth Africa
| | - David Wheeler
- School of Fundamental Sciences and Bio‐Protection Research CentreMassey UniversityPalmerston North4410New Zealand
- NSW Department of Primary IndustriesOrange Agricultural InstituteAustralia
| | - Murray P. Cox
- School of Fundamental Sciences and Bio‐Protection Research CentreMassey UniversityPalmerston North4410New Zealand
| | - Irene Barnes
- Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI)University of PretoriaPretoriaSouth Africa
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Ozturk IK, Dupont PY, Chettri P, McDougal R, Böhl OJ, Cox RJ, Bradshaw RE. Evolutionary relics dominate the small number of secondary metabolism genes in the hemibiotrophic fungus Dothistroma septosporum. Fungal Biol 2019; 123:397-407. [PMID: 31053329 DOI: 10.1016/j.funbio.2019.02.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [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: 10/28/2018] [Revised: 02/12/2019] [Accepted: 02/21/2019] [Indexed: 10/27/2022]
Abstract
Fungal secondary metabolites have important functions for the fungi that produce them, such as roles in virulence and competition. The hemibiotrophic pine needle pathogen Dothistroma septosporum has one of the lowest complements of secondary metabolite (SM) backbone genes of plant pathogenic fungi, indicating that this fungus produces a limited range of SMs. Amongst these SMs is dothistromin, a well-characterised polyketide toxin and virulence factor that is required for expansion of disease lesions in Dothistroma needle blight disease. Dothistromin genes are dispersed across six loci on one chromosome, rather than being clustered as for most SM genes. We explored other D. septosporum SM genes to determine if they are associated with gene clusters, and to predict what their likely products and functions might be. Of nine functional SM backbone genes in the D. septosporum genome, only four were expressed under a range of in planta and in culture conditions, one of which was the dothistromin PKS backbone gene. Of the other three expressed genes, gene knockout studies suggested that DsPks1 and DsPks2 are not required for virulence and attempts to determine a functional squalestatin-like SM product for DsPks2 were not successful. However preliminary evidence suggested that DsNps3, the only SM backbone gene to be most highly expressed in the early stage of disease, appears to be a virulence factor. Thus, despite the small number of SM backbone genes in D. septosporum, most of them appear to be poorly expressed or dispensable for virulence in planta. This work contributes to a growing body of evidence that many fungal secondary metabolite gene clusters might be non-functional and may be evolutionary relics.
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Affiliation(s)
- I Kutay Ozturk
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, 4410, New Zealand
| | - Pierre-Yves Dupont
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, 4410, New Zealand; Institute of Environmental Science and Research, Christchurch, 8041, New Zealand
| | - Pranav Chettri
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, 4410, New Zealand
| | - Rebecca McDougal
- Scion, NZ Forest Research Institute Ltd, Rotorua, 3010, New Zealand
| | - Ole J Böhl
- Institut für Organische Chemie, Leibniz Universität Hannover, Schneiderberg 1b, Hannover, 30167, Germany
| | - Russell J Cox
- Institut für Organische Chemie, Leibniz Universität Hannover, Schneiderberg 1b, Hannover, 30167, Germany
| | - Rosie E Bradshaw
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, 4410, New Zealand.
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5
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Chettri P, Dupont PY, Bradshaw RE. Chromatin-level regulation of the fragmented dothistromin gene cluster in the forest pathogen Dothistroma septosporum. Mol Microbiol 2018; 107:508-522. [DOI: 10.1111/mmi.13898] [Citation(s) in RCA: 11] [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] [Received: 09/21/2017] [Revised: 12/10/2017] [Accepted: 12/11/2017] [Indexed: 11/29/2022]
Affiliation(s)
- Pranav Chettri
- Bio-Protection Research Centre, Institute of Fundamental Sciences; Massey University; Palmerston North New Zealand
| | - Pierre-Yves Dupont
- Bio-Protection Research Centre, Institute of Fundamental Sciences; Massey University; Palmerston North New Zealand
| | - Rosie E. Bradshaw
- Bio-Protection Research Centre, Institute of Fundamental Sciences; Massey University; Palmerston North New Zealand
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6
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Ozturk IK, Chettri P, Dupont PY, Barnes I, McDougal RL, Moore GG, Sim A, Bradshaw RE. Evolution of polyketide synthesis in a Dothideomycete forest pathogen. Fungal Genet Biol 2017; 106:42-50. [PMID: 28690095 DOI: 10.1016/j.fgb.2017.07.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 06/27/2017] [Accepted: 07/05/2017] [Indexed: 11/16/2022]
Abstract
Fungal secondary metabolites have many important biological roles and some, like the toxic polyketide aflatoxin, have been intensively studied at the genetic level. Complete sets of polyketide synthase (PKS) genes can now be identified in fungal pathogens by whole genome sequencing and studied in order to predict the biosynthetic potential of those fungi. The pine needle pathogen Dothistroma septosporum is predicted to have only three functional PKS genes, a small number for a hemibiotrophic fungus. One of these genes is required for production of dothistromin, a polyketide virulence factor related to aflatoxin, whose biosynthetic genes are dispersed across one chromosome rather than being clustered. Here we evaluated the evolution of the other two genes, and their predicted gene clusters, using phylogenetic and population analyses. DsPks1 and its gene cluster are quite conserved amongst related fungi, whilst DsPks2 appears to be novel. The DsPks1 protein was predicted to be required for dihydroxynaphthalene (DHN) melanin biosynthesis but functional analysis of DsPks1 mutants showed that D. septosporum produced mainly dihydroxyphenylalanine (DOPA) melanin, which is produced by a PKS-independent pathway. Although the secondary metabolites made by these two PKS genes are not known, comparisons between strains of D. septosporum from different regions of the world revealed that both PKS core genes are under negative selection and we suggest they may have important cryptic roles in planta.
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Affiliation(s)
- I Kutay Ozturk
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North 4474, New Zealand.
| | - Pranav Chettri
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North 4474, New Zealand.
| | - Pierre-Yves Dupont
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North 4474, New Zealand.
| | - Irene Barnes
- Department of Genetics, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa.
| | | | - Geromy G Moore
- Southern Regional Research Center, Agricultural Research Service, USDA, New Orleans, LA 70124, USA.
| | - Andre Sim
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North 4474, New Zealand.
| | - Rosie E Bradshaw
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North 4474, New Zealand.
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7
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Bhadra A, Karmakar G, Nahak P, Chettri P, Roy B, Guha P, Mandal A, Nath R, Panda A. Impact of detergents on the physiochemical behavior of itraconazole loaded nanostructured lipid carriers. Colloids Surf A Physicochem Eng Asp 2017. [DOI: 10.1016/j.colsurfa.2016.12.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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8
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Chettri P, Bradshaw RE. LaeA negatively regulates dothistromin production in the pine needle pathogen Dothistroma septosporum. Fungal Genet Biol 2016; 97:24-32. [PMID: 27818262 DOI: 10.1016/j.fgb.2016.11.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [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: 08/22/2016] [Revised: 10/30/2016] [Accepted: 11/01/2016] [Indexed: 01/03/2023]
Abstract
In filamentous fungi both pathway-specific and global regulators regulate genes involved in the biosynthesis of secondary metabolites. LaeA is a global regulator that was named for its mutant phenotype, loss of aflR expression, due to its effect on the aflatoxin-pathway regulator AflR in Aspergillus spp. The pine needle pathogen Dothistroma septosporum produces a polyketide virulence factor, dothistromin, that is chemically related to aflatoxin and whose pathway genes are also regulated by an ortholog of AflR. However, dothistromin biosynthesis is distinctive because it is switched on during early (rather than late) exponential growth phase and the genes are dispersed in six loci across one chromosome instead of being clustered. It was therefore of interest to determine whether the function of the global regulator LaeA is conserved in D. septosporum. To address this question, a LaeA ortholog (DsLaeA) was identified and its function analyzed in D. septosporum. In contrast to aflatoxin production in Aspergillus spp., deletion of DsLaeA resulted in enhanced dothistromin production and increased expression of the pathway regulatory gene DsAflR. Although expression of other putative secondary metabolite genes in D. septosporum showed a range of different responses to loss of DsLaeA function, thin layer chromatography revealed increased levels of a previously unknown metabolite in DsLaeA mutants. In addition, these mutants exhibited reduced asexual sporulation, germination and hydrophobicity. Our data suggest that although the developmental regulatory role of DsLaeA is conserved, its role in the regulation of secondary metabolism differs from that of LaeA in A. nidulans and appears to be species specific. This study provides a step towards understanding fundamental differences in regulation of clustered and fragmented groups of secondary metabolite genes that may shed light on understanding functional adaptation in secondary metabolism.
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Affiliation(s)
- Pranav Chettri
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North 4474, New Zealand
| | - Rosie E Bradshaw
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North 4474, New Zealand.
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9
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Bradshaw RE, Guo Y, Sim AD, Kabir MS, Chettri P, Ozturk IK, Hunziker L, Ganley RJ, Cox MP. Genome-wide gene expression dynamics of the fungal pathogen Dothistroma septosporum throughout its infection cycle of the gymnosperm host Pinus radiata. Mol Plant Pathol 2016; 17:210-24. [PMID: 25919703 PMCID: PMC4746707 DOI: 10.1111/mpp.12273] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [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: 05/19/2023]
Abstract
We present genome-wide gene expression patterns as a time series through the infection cycle of the fungal pine needle blight pathogen, Dothistroma septosporum, as it invades its gymnosperm host, Pinus radiata. We determined the molecular changes at three stages of the disease cycle: epiphytic/biotrophic (early), initial necrosis (mid) and mature sporulating lesion (late). Over 1.7 billion combined plant and fungal reads were sequenced to obtain 3.2 million fungal-specific reads, which comprised as little as 0.1% of the sample reads early in infection. This enriched dataset shows that the initial biotrophic stage is characterized by the up-regulation of genes encoding fungal cell wall-modifying enzymes and signalling proteins. Later necrotrophic stages show the up-regulation of genes for secondary metabolism, putative effectors, oxidoreductases, transporters and starch degradation. This in-depth through-time transcriptomic study provides our first snapshot of the gene expression dynamics that characterize infection by this fungal pathogen in its gymnosperm host.
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Affiliation(s)
- Rosie E Bradshaw
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, 4474, New Zealand
| | - Yanan Guo
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, 4474, New Zealand
| | - Andre D Sim
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, 4474, New Zealand
| | - M Shahjahan Kabir
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, 4474, New Zealand
| | - Pranav Chettri
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, 4474, New Zealand
| | - Ibrahim K Ozturk
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, 4474, New Zealand
| | - Lukas Hunziker
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, 4474, New Zealand
| | - Rebecca J Ganley
- Scion, NZ Forest Research Institute Ltd, Rotorua, 3010, New Zealand
| | - Murray P Cox
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, 4474, New Zealand
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Bradshaw RE, Slot JC, Moore GG, Chettri P, de Wit PJGM, Ehrlich KC, Ganley ARD, Olson MA, Rokas A, Carbone I, Cox MP. Fragmentation of an aflatoxin-like gene cluster in a forest pathogen. New Phytol 2013; 198:525-535. [PMID: 23448391 DOI: 10.1111/nph.12161] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Accepted: 12/25/2012] [Indexed: 06/01/2023]
Abstract
Plant pathogens use a complex arsenal of weapons, such as toxic secondary metabolites, to invade and destroy their hosts. Knowledge of how secondary metabolite pathways evolved is central to understanding the evolution of host specificity. The secondary metabolite dothistromin is structurally similar to aflatoxins and is produced by the fungal pine pathogen Dothistroma septosporum. Our study focused on dothistromin genes, which are widely dispersed across one chromosome, to determine whether this unusual distributed arrangement evolved from an ancestral cluster. We combined comparative genomics and population genetics approaches to elucidate the origins of the dispersed arrangement of dothistromin genes over a broad evolutionary time-scale at the phylum, class and species levels. Orthologs of dothistromin genes were found in two major classes of fungi. Their organization is consistent with clustering of core pathway genes in a common ancestor, but with intermediate cluster fragmentation states in the Dothideomycetes fungi. Recombination hotspots in a D. septosporum population matched sites of gene acquisition and cluster fragmentation at higher evolutionary levels. The results suggest that fragmentation of a larger ancestral cluster gave rise to the arrangement seen in D. septosporum. We propose that cluster fragmentation may facilitate metabolic retooling and subsequent host adaptation of plant pathogens.
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Affiliation(s)
- Rosie E Bradshaw
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Jason C Slot
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, 37235, USA
| | - Geromy G Moore
- Southern Regional Research Center, Agricultural Research Service, USDA, New Orleans, LA, 70124, USA
| | - Pranav Chettri
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Pierre J G M de Wit
- Laboratory of Phytopathology, Wageningen University, Wageningen, the Netherlands
| | - Kenneth C Ehrlich
- Southern Regional Research Center, Agricultural Research Service, USDA, New Orleans, LA, 70124, USA
| | - Austen R D Ganley
- Institute of Natural Sciences, Massey University, Albany, New Zealand
| | - Malin A Olson
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Antonis Rokas
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, 37235, USA
| | - Ignazio Carbone
- Department of Plant Pathology, North Carolina State University, Raleigh, NC, 27695-7244, USA
| | - Murray P Cox
- Bio-Protection Research Centre, Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
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Chettri P, Calvo AM, Cary JW, Dhingra S, Guo Y, McDougal RL, Bradshaw RE. The veA gene of the pine needle pathogen Dothistroma septosporum regulates sporulation and secondary metabolism. Fungal Genet Biol 2011; 49:141-51. [PMID: 22227160 DOI: 10.1016/j.fgb.2011.11.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Revised: 11/18/2011] [Accepted: 11/21/2011] [Indexed: 02/06/2023]
Abstract
Fungi possess genetic systems to regulate the expression of genes involved in complex processes such as development and secondary metabolite biosynthesis. The product of the velvet gene veA, first identified and characterized in Aspergillus nidulans, is a key player in the regulation of both of these processes. Since its discovery and characterization in many Aspergillus species, VeA has been found to have similar functions in other fungi, including the Dothideomycete Mycosphaerella graminicola. Another Dothideomycete, Dothistroma septosporum, is a pine needle pathogen that produces dothistromin, a polyketide toxin very closely related to aflatoxin (AF) and sterigmatocystin (ST) synthesized by Aspergillus spp. Dothistromin is unusual in that, unlike most other secondary metabolites, it is produced mainly during the early exponential growth phase in culture. It was therefore of interest to determine whether the regulation of dothistromin production in D. septosporum differs from the regulation of AF/ST in Aspergillus spp. To begin to address this question, a veA ortholog was identified and its function analyzed in D. septosporum. Inactivation of the veA gene resulted in reduced dothistromin production and a corresponding decrease in expression of dothistromin biosynthetic genes. Expression of other putative secondary metabolite genes in D. septosporum such as polyketide synthases and non-ribosomal peptide synthases showed a range of different responses to loss of Ds-veA. Asexual sporulation was also significantly reduced in the mutants, accompanied by a reduction in the expression of a putative stuA regulatory gene. The mutants were, however, able to infect Pinus radiata seedlings and complete their life cycle under laboratory conditions. Overall this work suggests that D. septosporum has a veA ortholog that is involved in the control of both developmental and secondary metabolite biosynthetic pathways.
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Affiliation(s)
- Pranav Chettri
- Institute of Molecular BioSciences, Massey University, Palmerston North, New Zealand
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