Runaway repeats force expansion of the Phytophthora infestans genome

Sequencing of the potato late blight pathogen Phytophthora infestans provides insight into the structure and evolution of its genome

Gene amplification of the Hps locus in Glycine max

BACKGROUND: Hydrophobic protein from soybean (HPS) is an 8 kD cysteine-rich polypeptide that causes asthma in persons allergic to soybean dust. HPS is synthesized in the pod endocarp and deposited on the seed surface during development. Past evidence suggests that the protein may mediate the adherence or dehiscence of endocarp tissues during maturation and affect the lustre, or glossiness of the seed surface. RESULTS: A comparison of soybean germplasm by genomic DNA blot hybridization shows that the copy number and structure of the Hps locus is polymorphic among soybean cultivars and related species. Changes in Hps gene copy number were also detected by comparative genomic DNA hybridization using cDNA microarrays. The Hps copy number polymorphisms co-segregated with seed lustre phenotype and HPS surface protein in a cross between dull- and shiny-seeded soybeans. In soybean cultivar Harosoy 63, a minimum of 27 ± 5 copies of the Hps gene were estimated to be present in each haploid genome. The isolation and analysis of genomic clones indicates that the core Hps locus is comprised of a tandem array of reiterated units, with each 8.6 kb unit containing a single HPS open reading frame. CONCLUSION: This study shows that polymorphisms at the Hps locus arise from changes in the gene copy number via gene amplification. We present a model whereby Hps copy number modulates protein expression levels and seed lustre, and we suggest that gene amplification may result from selection pressures imposed on crop plants

Crowdsourcing genomic analyses of ash and ash dieback – power to the people

Ash dieback is a devastating fungal disease of ash trees that has swept across Europe and recently reached the UK. This emergent pathogen has received little study in the past and its effect threatens to overwhelm the ash population. In response to this we have produced some initial genomics datasets and taken the unusual step of releasing them to the scientific community for analysis without first performing our own. In this manner we hope to ‘crowdsource’ analyses and bring the expertise of the community to bear on this problem as quickly as possible. Our data has been released through our website at oadb.tsl.ac.uk and a public GitHub repository

Phytophthora sojae Avirulence Effector Avr3b is a Secreted NADH and ADP-ribose Pyrophosphorylase that Modulates Plant Immunity

Plants have evolved pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI) to protect themselves from infection by diverse pathogens. Avirulence (Avr) effectors that trigger plant ETI as a result of recognition by plant resistance (R) gene products have been identified in many plant pathogenic oomycetes and fungi. However, the virulence functions of oomycete and fungal Avr effectors remain largely unknown. Here, we combined bioinformatics and genetics to identify Avr3b, a new Avr gene from Phytophthora sojae, an oomycete pathogen that causes soybean root rot. Avr3b encodes a secreted protein with the RXLR host-targeting motif and C-terminal W and Nudix hydrolase motifs. Some isolates of P. sojae evade perception by the soybean R gene Rps3b through sequence mutation in Avr3b and lowered transcript accumulation. Transient expression of Avr3b in Nicotiana benthamiana increased susceptibility to P. capsici and P. parasitica, with significantly reduced accumulation of reactive oxygen species (ROS) around invasion sites. Biochemical assays confirmed that Avr3b is an ADP-ribose/NADH pyrophosphorylase, as predicted from the Nudix motif. Deletion of the Nudix motif of Avr3b abolished enzyme activity. Mutation of key residues in Nudix motif significantly impaired Avr3b virulence function but not the avirulence activity. Some Nudix hydrolases act as negative regulators of plant immunity, and thus Avr3b might be delivered into host cells as a Nudix hydrolase to impair host immunity. Avr3b homologues are present in several sequenced Phytophthora genomes, suggesting that Phytophthora pathogens might share similar strategies to suppress plant immunity

Sequence Variants of the Phytophthora sojae RXLR Effector Avr3a/5 Are Differentially Recognized by Rps3a and Rps5 in Soybean

The perception of Phytophthora sojae avirulence (Avr) gene products by corresponding soybean resistance (Rps) gene products causes effector triggered immunity. Past studies have shown that the Avr3a and Avr5 genes of P. sojae are genetically linked, and the Avr3a gene encoding a secreted RXLR effector protein was recently identified. We now provide evidence that Avr3a and Avr5 are allelic. Genetic mapping data from F2 progeny indicates that Avr3a and Avr5 co-segregate, and haplotype analysis of P. sojae strain collections reveal sequence and transcriptional polymorphisms that are consistent with a single genetic locus encoding Avr3a/5. Transformation of P. sojae and transient expression in soybean were performed to test how Avr3a/5 alleles interact with soybean Rps3a and Rps5. Over-expression of Avr3a/5 in a P. sojae strain that is normally virulent on Rps3a and Rps5 results in avirulence to Rps3a and Rps5; whereas silencing of Avr3a/5 causes gain of virulence in a P. sojae strain that is normally avirulent on Rps3a and Rps5 soybean lines. Transient expression and co-bombardment with a reporter gene confirms that Avr3a/5 triggers cell death in Rps5 soybean leaves in an appropriate allele-specific manner. Sequence analysis of the Avr3a/5 gene identifies crucial residues in the effector domain that distinguish recognition by Rps3a and Rps5

Heterologous expression screens in Nicotiana benthamiana identify a candidate effector of the wheat Yellow Rust Pathogen that associates with processing bodies

Rust fungal pathogens of wheat (Triticum spp.) affect crop yields worldwide. The molecular mechanisms underlying the virulence of these pathogens remain elusive, due to the limited availability of suitable molecular genetic research tools. Notably, the inability to perform high-throughput analyses of candidate virulence proteins (also known as effectors) impairs progress. We previously established a pipeline for the fast-forward screens of rust fungal candidate effectors in the model plant Nicotiana benthamiana. This pipeline involves selecting candidate effectors in silico and performing cell biology and protein-protein interaction assays in planta to gain insight into the putative functions of candidate effectors. In this study, we used this pipeline to identify and characterize sixteen candidate effectors from the wheat yellow rust fungal pathogen Puccinia striiformis f sp tritici. Nine candidate effectors targeted a specific plant subcellular compartment or protein complex, providing valuable information on their putative functions in plant cells. One candidate effector, PST02549, accumulated in processing bodies (P-bodies), protein complexes involved in mRNA decapping, degradation, and storage. PST02549 also associates with the P-body-resident ENHANCER OF mRNA DECAPPING PROTEIN 4 (EDC4) from N. benthamiana and wheat. We propose that P-bodies are a novel plant cell compartment targeted by pathogen effectors

Molecular diversity of anthracnose pathogen populations associated with UK strawberry production suggests multiple introductions of three different Colletotrichum species.

Fragaria × ananassa (common name: strawberry) is a globally cultivated hybrid species belonging to Rosaceae family. Colletotrichum acutatum sensu lato (s.l.) is considered to be the second most economically important pathogen worldwide affecting strawberries. A collection of 148 Colletotrichum spp. isolates including 67 C. acutatum s.l. isolates associated with the phytosanitary history of UK strawberry production were used to characterize multi-locus genetic variation of this pathogen in the UK, relative to additional reference isolates that represent a worldwide sampling of the diversity of the fungus. The evidence indicates that three different species C. nymphaeae, C. godetiae and C. fioriniae are associated with strawberry production in the UK, which correspond to previously designated genetic groups A2, A4 and A3, respectively. Among these species, 12 distinct haplotypes were identified suggesting multiple introductions into the country. A subset of isolates was also used to compare aggressiveness in causing disease on strawberry plants and fruits. Isolates belonging to C. nymphaeae, C. godetiae and C. fioriniae representative of the UK anthracnose pathogen populations showed variation in their aggressiveness. Among the three species, C. nymphaeae and C. fioriniae appeared to be more aggressive compared to C. godetiae. This study highlights the genetic and pathogenic heterogeneity of the C. acutatum s.l. populations introduced into the UK linked to strawberry production

Genome sequences of two Phytophthora species responsible for Sudden Oak Death and Soybean Root Rot provide novel insights into their evolutionary origins and mechanisms of pathogenesis

The approximately 60 species of Phytophthora are all destructive pathogens, causing rots of roots, stems, leaves and fruits of a wide range of agriculturally and ornamentally important plants (1). Some species, such as P. cinnamomi, P. parasitica and P. cactorum, each attack hundreds of different plant host species, whereas others are more restricted. Some of the crops where Phytophthora infections cause the greatest financial losses include potato, soybean, tomato, alfalfa, tobacco, peppers, cucurbits, pineapple, strawberry, raspberry and a wide range of perennial tree crops, especially citrus, avocado, almonds, walnuts, apples and cocoa, and they also heavily affect the ornamental, nursery and forestry industries. The economic damage overall to crops in the United States by Phytophthora species is estimated in the tens of billions of dollars, including the costs of control measures, and worldwide it is many times this amount (1). In the northern midwest of the U.S., P. sojae causes $200 million in annual losses to soybean alone, and worldwide causes around$1-2 billion in losses per year. P. infestans infections resulted in the Irish potato famine last century and continues to be a difficult and worsening problem for potato and tomato growers worldwide, with worldwide costs estimated at $5 billion per year

The Use of Genus-Specific Amplicon Pyrosequencing to Assess Phytophthora Species Diversity Using eDNA from Soil and Water in Northern Spain

[EN] Phytophthora is one of the most important and aggressive plant pathogenic genera in agriculture and forestry. Early detection and identification of its pathways of infection and spread are of high importance to minimize the threat they pose to natural ecosystems. eDNA was extracted from soil and water from forests and plantations in the north of Spain. Phytophthora-specific primers were adapted for use in high-throughput Sequencing (HTS). Primers were tested in a control reaction containing eight Phytophthora species and applied to water and soil eDNA samples from northern Spain. Different score coverage threshold values were tested for optimal Phytophthora species separation in a custom-curated database and in the control reaction. Clustering at 99% was the optimal criteria to separate most of the Phytophthora species. Multiple Molecular Operational Taxonomic Units (MOTUs) corresponding to 36 distinct Phytophthora species were amplified in the environmental samples. Pyrosequencing of amplicons from soil samples revealed low Phytophthora diversity (13 species) in comparison with the 35 species detected in water samples. Thirteen of the MOTUs detected in rivers and streams showed no close match to sequences in international sequence databases, revealing that eDNA pyrosequencing is a useful strategy to assess Phytophthora species diversity in natural ecosystems.This project has been supported by the Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria (EUPHRESCO-CEP: "Current and Emerging Phytophthoras: Research Supporting Risk Assessment And Risk Management"). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Català, S.; Pérez Sierra, AM.; Abad Campos, P. (2015). The Use of Genus-Specific Amplicon Pyrosequencing to Assess Phytophthora Species Diversity Using eDNA from Soil and Water in Northern Spain. PLoS ONE. 10(3):1-14. doi:10.1371/journal.pone.0119311S114103REICHARD, S. H., & WHITE, P. (2001). Horticulture as a Pathway of Invasive Plant Introductions in the United States. BioScience, 51(2), 103. doi:10.1641/0006-3568(2001)051[0103:haapoi]2.0.co;2Brasier, C. M. (2008). The biosecurity threat to the UK and global environment from international trade in plants. Plant Pathology, 57(5), 792-808. doi:10.1111/j.1365-3059.2008.01886.xTABERLET, P., COISSAC, E., HAJIBABAEI, M., & RIESEBERG, L. H. (2012). Environmental DNA. Molecular Ecology, 21(8), 1789-1793. doi:10.1111/j.1365-294x.2012.05542.xSogin, M. L., Morrison, H. G., Huber, J. A., Welch, D. M., Huse, S. M., Neal, P. R., … Herndl, G. J. (2006). Microbial diversity in the deep sea and the underexplored «rare biosphere». Proceedings of the National Academy of Sciences, 103(32), 12115-12120. doi:10.1073/pnas.0605127103Roesch, L. F. W., Fulthorpe, R. R., Riva, A., Casella, G., Hadwin, A. K. M., Kent, A. D., … Triplett, E. W. (2007). Pyrosequencing enumerates and contrasts soil microbial diversity. The ISME Journal, 1(4), 283-290. doi:10.1038/ismej.2007.53Acosta-Martínez, V., Dowd, S., Sun, Y., & Allen, V. (2008). Tag-encoded pyrosequencing analysis of bacterial diversity in a single soil type as affected by management and land use. Soil Biology and Biochemistry, 40(11), 2762-2770. doi:10.1016/j.soilbio.2008.07.022Jumpponen, A., & Jones, K. L. (2009). Massively parallel 454 sequencing indicates hyperdiverse fungal communities in temperateQuercus macrocarpaphyllosphere. New Phytologist, 184(2), 438-448. doi:10.1111/j.1469-8137.2009.02990.xNilsson, R. H., Ryberg, M., Abarenkov, K., Sjökvist, E., & Kristiansson, E. (2009). The ITS region as a target for characterization of fungal communities using emerging sequencing technologies. FEMS Microbiology Letters, 296(1), 97-101. doi:10.1111/j.1574-6968.2009.01618.xCoince, A., Caël, O., Bach, C., Lengellé, J., Cruaud, C., Gavory, F., … Buée, M. (2013). Below-ground fine-scale distribution and soil versus fine root detection of fungal and soil oomycete communities in a French beech forest. Fungal Ecology, 6(3), 223-235. doi:10.1016/j.funeco.2013.01.002Vannini, A., Bruni, N., Tomassini, A., Franceschini, S., & Vettraino, A. M. (2013). Pyrosequencing of environmental soil samples reveals biodiversity of thePhytophthoraresident community in chestnut forests. FEMS Microbiology Ecology, 85(3), 433-442. doi:10.1111/1574-6941.12132Jerde, C. L., Mahon, A. R., Chadderton, W. L., & Lodge, D. M. (2011). «Sight-unseen» detection of rare aquatic species using environmental DNA. Conservation Letters, 4(2), 150-157. doi:10.1111/j.1755-263x.2010.00158.xMonchy, S., Sanciu, G., Jobard, M., Rasconi, S., Gerphagnon, M., Chabé, M., … Sime-Ngando, T. (2011). Exploring and quantifying fungal diversity in freshwater lake ecosystems using rDNA cloning/sequencing and SSU tag pyrosequencing. Environmental Microbiology, 13(6), 1433-1453. doi:10.1111/j.1462-2920.2011.02444.xJobard, M., Rasconi, S., Solinhac, L., Cauchie, H.-M., & Sime-Ngando, T. (2012). Molecular and morphological diversity of fungi and the associated functions in three European nearby lakes. Environmental Microbiology, 14(9), 2480-2494. doi:10.1111/j.1462-2920.2012.02771.xLivermore, J. A., & Mattes, T. E. (2013). Phylogenetic detection of novel Cryptomycota in an Iowa (United States) aquifer and from previously collected marine and freshwater targeted high-throughput sequencing sets. Environmental Microbiology, 15(8), 2333-2341. doi:10.1111/1462-2920.12106NAKAYAMA, J., JIANG, J., WATANABE, K., CHEN, K., NINXIN, H., MATSUDA, K., … LEE, Y.-K. (2013). Up to Species-level Community Analysis of Human Gut Microbiota by 16S rRNA Amplicon Pyrosequencing. Bioscience of Microbiota, Food and Health, 32(2), 69-76. doi:10.12938/bmfh.32.69CREER, S., & SINNIGER, F. (2012). Cosmopolitanism of microbial eukaryotes in the global deep seas. Molecular Ecology, 21(5), 1033-1035. doi:10.1111/j.1365-294x.2012.05437.xDavey, M. L., Heegaard, E., Halvorsen, R., Kauserud, H., & Ohlson, M. (2012). Amplicon-pyrosequencing-based detection of compositional shifts in bryophyte-associated fungal communities along an elevation gradient. Molecular Ecology, 22(2), 368-383. doi:10.1111/mec.12122Weber, C. F., Vilgalys, R., & Kuske, C. R. (2013). Changes in Fungal Community Composition in Response to Elevated Atmospheric CO2 and Nitrogen Fertilization Varies with Soil Horizon. Frontiers in Microbiology, 4. doi:10.3389/fmicb.2013.00078Bergmark, L., Poulsen, P. H. B., Al-Soud, W. A., Norman, A., Hansen, L. H., & Sørensen, S. J. (2012). Assessment of the specificity of Burkholderia and Pseudomonas qPCR assays for detection of these genera in soil using 454 pyrosequencing. FEMS Microbiology Letters, 333(1), 77-84. doi:10.1111/j.1574-6968.2012.02601.xLi, L., Abu Al-Soud, W., Bergmark, L., Riber, L., Hansen, L. H., Magid, J., & Sørensen, S. J. (2013). Investigating the Diversity of Pseudomonas spp. in Soil Using Culture Dependent and Independent Techniques. Current Microbiology, 67(4), 423-430. doi:10.1007/s00284-013-0382-xSCHENA, L., HUGHES, K. J. D., & COOKE, D. E. L. (2006). Detection and quantification ofPhytophthora ramorum,P. kernoviae,P. citricolaandP. quercinain symptomatic leaves by multiplex real-time PCR. Molecular Plant Pathology, 7(5), 365-379. doi:10.1111/j.1364-3703.2006.00345.xTooley, P. W., Martin, F. N., Carras, M. M., & Frederick, R. D. (2006). Real-Time Fluorescent Polymerase Chain Reaction Detection ofPhytophthora ramorumandPhytophthora pseudosyringaeUsing Mitochondrial Gene Regions. Phytopathology, 96(4), 336-345. doi:10.1094/phyto-96-0336Pavón, C. F., Babadoost, M., & Lambert, K. N. (2008). Quantification of Phytophthora capsici Oospores in Soil by Sieving-Centrifugation and Real-Time Polymerase Chain Reaction. Plant Disease, 92(1), 143-149. doi:10.1094/pdis-92-1-0143Than, D. J., Hughes, K. J. D., Boonhan, N., Tomlinson, J. A., Woodhall, J. W., & Bellgard, S. E. (2013). A TaqMan real-time PCR assay for the detection ofPhytophthora‘taxon Agathis’ in soil, pathogen of Kauri in New Zealand. Forest Pathology, 43(4), 324-330. doi:10.1111/efp.12034Chen, W., Djama, Z. R., Coffey, M. D., Martin, F. N., Bilodeau, G. J., Radmer, L., … Lévesque, C. A. (2013). Membrane-Based Oligonucleotide Array Developed from Multiple Markers for the Detection of Many Phytophthora Species. Phytopathology, 103(1), 43-54. doi:10.1094/phyto-04-12-0092-rScibetta, S., Schena, L., Chimento, A., Cacciola, S. O., & Cooke, D. E. L. (2012). A molecular method to assess Phytophthora diversity in environmental samples. Journal of Microbiological Methods, 88(3), 356-368. doi:10.1016/j.mimet.2011.12.012Català S, Pérez-Sierra A, Berbegal M, Abad-Campos P. First approach into the knowledge of the Phytophthora species diversity in Mediterranean holm oak forests based on 454 parallel amplicon pyrosequencing of soil samples. Phytophthora in Forest and Natural Ecosystems 6th International IUFRO Working Party 7.02.09 Meeting, Córdoba, Spain, pp 34; 2012.Català S, Pérez-Sierra A, Beltrán A, Abad-Campos P. Next Generation Sequencing shows Phytophthora species diversity in soil samples of Macaronesian laurel forests from the Canary Islands. Phytophthora in Forest and Natural Ecosystems 6th International IUFRO Working Party 7.02.09 Meeting, Córdoba, Spain, pp. 86; 2012.Cooke, D. E. L., Drenth, A., Duncan, J. M., Wagels, G., & Brasier, C. M. (2000). A Molecular Phylogeny of Phytophthora and Related Oomycetes. Fungal Genetics and Biology, 30(1), 17-32. doi:10.1006/fgbi.2000.1202Andrews S. FastQC: a quality control tool for high throughput sequence data. Available: http://www.bioinformatics.bbsrc.ac.uk/projects/fastqc/Chou, H.-H., & Holmes, M. H. (2001). DNA sequence quality trimming and vector removal. Bioinformatics, 17(12), 1093-1104. doi:10.1093/bioinformatics/17.12.1093Altschul, S. (1997). Gapped BLAST and PSI-BLAST: a new generation of protein database search programs. Nucleic Acids Research, 25(17), 3389-3402. doi:10.1093/nar/25.17.3389Edgar, R. C. (2004). MUSCLE: multiple sequence alignment with high accuracy and high throughput. Nucleic Acids Research, 32(5), 1792-1797. doi:10.1093/nar/gkh340Gouy, M., Guindon, S., & Gascuel, O. (2009). SeaView Version 4: A Multiplatform Graphical User Interface for Sequence Alignment and Phylogenetic Tree Building. Molecular Biology and Evolution, 27(2), 221-224. doi:10.1093/molbev/msp259Park, J., Park, B., Veeraraghavan, N., Jung, K., Lee, Y.-H., Blair, J. E., … Kang, S. (2008). Phytophthora Database: A Forensic Database Supporting the Identification and Monitoring of Phytophthora. Plant Disease, 92(6), 966-972. doi:10.1094/pdis-92-6-0966Vettraino, A. M., Bonants, P., Tomassini, A., Bruni, N., & Vannini, A. (2012). Pyrosequencing as a tool for the detection ofPhytophthoraspecies: error rate and risk of false Molecular Operational Taxonomic Units. Letters in Applied Microbiology, 55(5), 390-396. doi:10.1111/j.1472-765x.2012.03310.xJung, T., & Burgess, T. I. (2009). Re-evaluation of Phytophthora citricola isolates from multiple woody hosts in Europe and North America reveals a new species, Phytophthora plurivora sp. nov. Persoonia - Molecular Phylogeny and Evolution of Fungi, 22(1), 95-110. doi:10.3767/003158509x442612Deagle, B. E., Eveson, J. P., & Jarman, S. N. (2006). Quantification of damage in DNA recovered from highly degraded samples – a case study on DNA in faeces. Frontiers in Zoology, 3(1). doi:10.1186/1742-9994-3-11Dejean, T., Valentini, A., Duparc, A., Pellier-Cuit, S., Pompanon, F., Taberlet, P., & Miaud, C. (2011). Persistence of Environmental DNA in Freshwater Ecosystems. PLoS ONE, 6(8), e23398. doi:10.1371/journal.pone.0023398Guha Roy S, Grunwald NJ. The plant destroyer genus Phytophthora in the 21st century. In book: Review of Plant Pathology, Edition: Volume 6, Publisher: Scientific Publishers (India), Jodhpur, Editors: B.N.Chakraborty, B.B.L.Thakore, pp. In press; 2014.Brasier, C. M., Cooke, D. E. L., Duncan, J. M., & Hansen, E. M. (2003). Multiple new phenotypic taxa from trees and riparian ecosystems in Phytophthora gonapodyides-P. megasperma ITS Clade 6, which tend to be high-temperature tolerant and either inbreeding or sterile. Mycological Research, 107(3), 277-290. doi:10.1017/s095375620300738xHüberli, D., Hardy, G. E. S. J., White, D., Williams, N., & Burgess, T. I. (2013). Fishing for Phytophthora from Western Australia’s waterways: a distribution and diversity survey. Australasian Plant Pathology, 42(3), 251-260. doi:10.1007/s13313-012-0195-6Jung, T., Stukely, M. J. C., Hardy, G. E. S. J., White, D., Paap, T., Dunstan, W. A., & Burgess, T. I. (2011). Multiple new Phytophthora species from ITS Clade 6 associated with natural ecosystems in Australia: evolutionary and ecological implications. Persoonia - Molecular Phylogeny and Evolution of Fungi, 26(1), 13-39. doi:10.3767/003158511x557577Brasier, C. M., Sanchez-Hernandez, E., & Kirk, S. A. (2003). Phytophthora inundata sp. nov., a part heterothallic pathogen of trees and shrubs in wet or flooded soils. Mycological Research, 107(4), 477-484. doi:10.1017/s0953756203007548Hansen, E. M., Reeser, P. W., & Sutton, W. (2012). PhytophthoraBeyond Agriculture. Annual Review of Phytopathology, 50(1), 359-378. doi:10.1146/annurev-phyto-081211-172946Reeser, P. W., Sutton, W., Hansen, E. M., Remigi, P., & Adams, G. C. (2011). Phytophthora species in forest streams in Oregon and Alaska. Mycologia, 103(1), 22-35. doi:10.3852/10-013Nechwatal, J., Bakonyi, J., Cacciola, S. O., Cooke, D. E. L., Jung, T., Nagy, Z. Á., … Brasier, C. M. (2012). The morphology, behaviour and molecular phylogeny ofPhytophthorataxon Salixsoil and its redesignation asPhytophthora lacustrissp. nov. Plant Pathology, 62(2), 355-369. doi:10.1111/j.1365-3059.2012.02638.xHuai, W. -x., Tian, G., Hansen, E. M., Zhao, W. -x., Goheen, E. M., Grünwald, N. J., & Cheng, C. (2013). Identification ofPhytophthoraspecies baited and isolated from forest soil and streams in northwestern Yunnan province, China. Forest Pathology, 43(2), 87-103. doi:10.1111/efp.12015Oh, E., Gryzenhout, M., Wingfield, B. D., Wingfield, M. J., & Burgess, T. I. (2013). Surveys of soil and water reveal a goldmine of Phytophthora diversity in South African natural ecosystems. IMA Fungus, 4(1), 123-131. doi:10.5598/imafungus.2013.04.01.1

Variation in capsidiol sensitivity between Phytophthora infestans and Phytophthora capsici is consistent with their host range.

Plants protect themselves against a variety of invading pathogenic organisms via sophisticated defence mechanisms. These responses include deployment of specialized antimicrobial compounds, such as phytoalexins, that rapidly accumulate at pathogen infection sites. However, the extent to which these compounds contribute to species-level resistance and their spectrum of action remain poorly understood. Capsidiol, a defense related phytoalexin, is produced by several solanaceous plants including pepper and tobacco during microbial attack. Interestingly, capsidiol differentially affects growth and germination of the oomycete pathogens Phytophthora infestans and Phytophthora capsici, although the underlying molecular mechanisms remain unknown. In this study we revisited the differential effect of capsidiol on P. infestans and P. capsici, using highly pure capsidiol preparations obtained from yeast engineered to express the capsidiol biosynthetic pathway. Taking advantage of transgenic Phytophthora strains expressing fluorescent markers, we developed a fluorescence-based method to determine the differential effect of capsidiol on Phytophtora growth. Using these assays, we confirm major differences in capsidiol sensitivity between P. infestans and P. capsici and demonstrate that capsidiol alters the growth behaviour of both Phytophthora species. Finally, we report intraspecific variation within P. infestans isolates towards capsidiol tolerance pointing to an arms race between the plant and the pathogens in deployment of defence related phytoalexins