1
|
Kharel A, Rookes J, Ziemann M, Cahill D. Viable protoplast isolation, organelle visualization and transformation of the globally distributed plant pathogen Phytophthora cinnamomi. PROTOPLASMA 2024:10.1007/s00709-024-01953-y. [PMID: 38702562 DOI: 10.1007/s00709-024-01953-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 04/11/2024] [Indexed: 05/06/2024]
Abstract
Phytophthora cinnamomi is an oomycete plant pathogen with a host range of almost 5000 plant species worldwide and therefore poses a serious threat to biodiversity. Omics technology has provided significant progress in our understanding of oomycete biology, however, transformation studies of Phytophthora for gene functionalisation are still in their infancy. Only a limited number of Phytophthora species have been successfully transformed and gene edited to elucidate the role of particular genes. There is a need to escalate our efforts to understand molecular processes, gene regulation and infection mechanisms of the pathogen to enable us to develop new disease management strategies. The primary obstacle hindering the advancement of transformation studies in Phytophthora is their challenging and unique nature, coupled with our limited comprehension of why they remain such an intractable system to work with. In this study, we have identified some of the key factors associated with the recalcitrant nature of P. cinnamomi. We have incorporated fluorescence microscopy and flow cytometry along with the organelle-specific dyes, fluorescein diacetate, Hoechst 33342 and MitoTracker™ Red CMXRos, to assess P. cinnamomi-derived protoplast populations. This approach has also provided valuable insights into the broader cell biology of Phytophthora. Furthermore, we have optimized the crucial steps that allow transformation of P. cinnamomi and have generated transformed isolates that express a cyan fluorescent protein, with a transformation efficiency of 19.5%. We therefore provide a platform for these methodologies to be applied for the transformation of other Phytophthora species and pave the way for future gene functionalisation studies.
Collapse
Affiliation(s)
- Aayushree Kharel
- School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds Campus, Waurn Ponds, VIC, 3216, Australia
| | - James Rookes
- School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds Campus, Waurn Ponds, VIC, 3216, Australia
| | - Mark Ziemann
- School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds Campus, Waurn Ponds, VIC, 3216, Australia
- Burnet Institute, Melbourne, Australia
| | - David Cahill
- School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds Campus, Waurn Ponds, VIC, 3216, Australia.
| |
Collapse
|
2
|
Rojas-Rojas FU, Vega-Arreguín JC. Epigenetic insight into regulatory role of chromatin covalent modifications in lifecycle and virulence of Phytophthora. ENVIRONMENTAL MICROBIOLOGY REPORTS 2021; 13:445-457. [PMID: 33876568 DOI: 10.1111/1758-2229.12954] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 04/12/2021] [Accepted: 04/14/2021] [Indexed: 06/12/2023]
Abstract
The Oomycota phylum includes fungi-like filamentous microorganisms classified as plant pathogens. The most destructive genus within oomycetes is Phytophthora, which causes diseases in plants of economic importance in agriculture, forestry and ornamental. Phytophthora species are widespread worldwide and some of them enable adaptation to different hosts and environmental changes. The development of sexual and asexual reproductive structures and the secretion of proteins to control plant immunity are critical for the adaptative lifestyle. However, molecular mechanisms underlying the adaptation of Phytophthora to different hosts and environmental changes are poorly understood. In the last decade, the role of epigenetics has gained attention, and important evidence has demonstrated the potential role of chromatin covalent modifications, such as DNA methylation and histone acetylation/methylation, in the regulation of gene expression during Phytophthora development and plant infection. Here, we review for the first time the evidence of the potential role of chromatin covalent modifications in the lifecycle of the phytopathogenic genus Phytophthora, including virulence, and host and environment adaptation processes.
Collapse
Affiliation(s)
- Fernando Uriel Rojas-Rojas
- Laboratorio de Ciencias AgroGenómicas, Escuela Nacional de Estudios Superiores Unidad León, Universidad Nacional Autónoma de México (ENES - León, UNAM), Blvd. UNAM 2011, León, Guanajuato, 37684, Mexico
- Laboratorio Nacional PlanTECC, Escuela Nacional de Estudios Superiores Unidad León, Universidad Nacional Autónoma de México (ENES - León, UNAM), Blvd. UNAM 2011, León, Guanajuato, 37684, Mexico
| | - Julio C Vega-Arreguín
- Laboratorio de Ciencias AgroGenómicas, Escuela Nacional de Estudios Superiores Unidad León, Universidad Nacional Autónoma de México (ENES - León, UNAM), Blvd. UNAM 2011, León, Guanajuato, 37684, Mexico
- Laboratorio Nacional PlanTECC, Escuela Nacional de Estudios Superiores Unidad León, Universidad Nacional Autónoma de México (ENES - León, UNAM), Blvd. UNAM 2011, León, Guanajuato, 37684, Mexico
| |
Collapse
|
3
|
Ah‐Fong AM, Boyd AM, Matson ME, Judelson HS. A Cas12a-based gene editing system for Phytophthora infestans reveals monoallelic expression of an elicitor. MOLECULAR PLANT PATHOLOGY 2021; 22:737-752. [PMID: 33724663 PMCID: PMC8126191 DOI: 10.1111/mpp.13051] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 01/28/2021] [Accepted: 02/16/2021] [Indexed: 05/03/2023]
Abstract
Phytophthora infestans is a destructive pathogen of potato and a model for investigations of oomycete biology. The successful application of a CRISPR gene editing system to P. infestans is so far unreported. We discovered that it is difficult to express CRISPR/Cas9 but not a catalytically inactive form in transformants, suggesting that the active nuclease is toxic. We were able to achieve editing with CRISPR/Cas12a using vectors in which the nuclease and its guide RNA were expressed from a single transcript. Using the elicitor gene Inf1 as a target, we observed editing of one or both alleles in up to 13% of transformants. Editing was more efficient when guide RNA processing relied on the Cas12a direct repeat instead of ribozyme sequences. INF1 protein was not made when both alleles were edited in the same transformant, but surprisingly also when only one allele was altered. We discovered that the isolate used for editing, 1306, exhibited monoallelic expression of Inf1 due to insertion of a copia-like element in the promoter of one allele. The element exhibits features of active retrotransposons, including a target site duplication, long terminal repeats, and an intact polyprotein reading frame. Editing occurred more often on the transcribed allele, presumably due to differences in chromatin structure. The Cas12a system not only provides a tool for modifying genes in P. infestans, but also for other members of the genus by expanding the number of editable sites. Our work also highlights a natural mechanism that remodels oomycete genomes.
Collapse
Affiliation(s)
- Audrey M.V. Ah‐Fong
- Department of Microbiology and Plant PathologyUniversity of CaliforniaRiversideCaliforniaUSA
| | - Amy M. Boyd
- Department of Microbiology and Plant PathologyUniversity of CaliforniaRiversideCaliforniaUSA
| | - Michael E.H. Matson
- Department of Microbiology and Plant PathologyUniversity of CaliforniaRiversideCaliforniaUSA
| | - Howard S. Judelson
- Department of Microbiology and Plant PathologyUniversity of CaliforniaRiversideCaliforniaUSA
| |
Collapse
|
4
|
Vu AL, Leesutthiphonchai W, Ah-Fong AMV, Judelson HS. Defining Transgene Insertion Sites and Off-Target Effects of Homology-Based Gene Silencing Informs the Application of Functional Genomics Tools in Phytophthora infestans. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2019; 32:915-927. [PMID: 30811313 DOI: 10.1094/mpmi-09-18-0265-ta] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
DNA transformation and homology-based transcriptional silencing are frequently used to assess gene function in Phytophthora spp. Since unplanned side-effects of these tools are not well-characterized, we used P. infestans to study plasmid integration sites and whether knockdowns caused by homology-dependent silencing spread to other genes. Insertions occurred both in gene-dense and gene-sparse regions but disproportionately near the 5' ends of genes, which disrupted native coding sequences. Microhomology at the recombination site between plasmid and chromosome was common. Studies of transformants silenced for 12 different gene targets indicated that neighbors within 500 nt were often cosilenced, regardless of whether hairpin or sense constructs were employed and the direction of transcription of the target. However, this cis spreading of silencing did not occur in all transformants obtained with the same plasmid. Genome-wide studies indicated that unlinked genes with partial complementarity with the silencing-inducing transgene were not usually down-regulated. We learned that hairpin or sense transgenes were not cosilenced with the target in all transformants, which informs how screens for silencing should be performed. We conclude that transformation and gene silencing can be reliable tools for functional genomics in Phytophthora spp. but must be used carefully, especially by testing for the spread of silencing to genes flanking the target.
Collapse
Affiliation(s)
- Andrea L Vu
- Department of Microbiology and Plant Pathology, University of California, Riverside, CA 92521, U.S.A
| | | | - Audrey M V Ah-Fong
- Department of Microbiology and Plant Pathology, University of California, Riverside, CA 92521, U.S.A
| | - Howard S Judelson
- Department of Microbiology and Plant Pathology, University of California, Riverside, CA 92521, U.S.A
| |
Collapse
|
5
|
Bollmann SR, Fang Y, Press CM, Tyler BM, Grünwald NJ. Diverse Evolutionary Trajectories for Small RNA Biogenesis Genes in the Oomycete Genus Phytophthora. FRONTIERS IN PLANT SCIENCE 2016; 7:284. [PMID: 27014308 PMCID: PMC4791657 DOI: 10.3389/fpls.2016.00284] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 02/22/2016] [Indexed: 05/10/2023]
Abstract
Gene regulation by small RNA pathways is ubiquitous among eukaryotes, but little is known about small RNA pathways in the Stramenopile kingdom. Phytophthora, a genus of filamentous oomycetes, contains many devastating plant pathogens, causing multibillion-dollar damage to crops, ornamental plants, and natural environments. The genomes of several oomycetes including Phytophthora species such as the soybean pathogen P. sojae, have been sequenced, allowing evolutionary analysis of small RNA-processing enzymes. This study examined the evolutionary origins of the oomycete small RNA-related genes Dicer-like (DCL), and RNA-dependent RNA polymerase (RDR) through broad phylogenetic analyses of the key domains. Two Dicer gene homologs, DCL1 and DCL2, and one RDR homolog were cloned and analyzed from P. sojae. Gene expression analysis revealed only minor changes in transcript levels among different life stages. Oomycete DCL1 homologs clustered with animal and plant Dicer homologs in evolutionary trees, whereas oomycete DCL2 homologs clustered basally to the tree along with Drosha homologs. Phylogenetic analysis of the RDR homologs confirmed a previous study that suggested the last common eukaryote ancestor possessed three RDR homologs, which were selectively retained or lost in later lineages. Our analysis clarifies the position of some Unikont and Chromalveolate RDR lineages within the tree, including oomycete homologs. Finally, we analyzed alterations in the domain structure of oomycete Dicer and RDR homologs, specifically focusing on the proposed domain transfer of the DEAD-box helicase domain from Dicer to RDR. Implications of the oomycete domain structure are discussed, and possible roles of the two oomycete Dicer homologs are proposed.
Collapse
Affiliation(s)
- Stephanie R. Bollmann
- Horticultural Crop Research Unit, USDA-Agricultural Research ServiceCorvallis, OR, USA
| | - Yufeng Fang
- Department of Botany and Plant Pathology and Center for Genome Biology and Biocomputing, Oregon State UniversityCorvallis, OR, USA
- Interdisciplinary Ph.D. Program in Genetics, Bioinformatics and Computational Biology, Virginia TechBlacksburg, VA, USA
| | - Caroline M. Press
- Horticultural Crop Research Unit, USDA-Agricultural Research ServiceCorvallis, OR, USA
| | - Brett M. Tyler
- Department of Botany and Plant Pathology and Center for Genome Biology and Biocomputing, Oregon State UniversityCorvallis, OR, USA
| | - Niklaus J. Grünwald
- Horticultural Crop Research Unit, USDA-Agricultural Research ServiceCorvallis, OR, USA
- Department of Botany and Plant Pathology and Center for Genome Biology and Biocomputing, Oregon State UniversityCorvallis, OR, USA
- *Correspondence: Niklaus J. Grünwald
| |
Collapse
|
6
|
Poidevin L, Andreeva K, Khachatoorian C, Judelson HS. Comparisons of Ribosomal Protein Gene Promoters Indicate Superiority of Heterologous Regulatory Sequences for Expressing Transgenes in Phytophthora infestans. PLoS One 2015; 10:e0145612. [PMID: 26716454 PMCID: PMC4696810 DOI: 10.1371/journal.pone.0145612] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 12/07/2015] [Indexed: 12/14/2022] Open
Abstract
Molecular genetics approaches in Phytophthora research can be hampered by the limited number of known constitutive promoters for expressing transgenes and the instability of transgene activity. We have therefore characterized genes encoding the cytoplasmic ribosomal proteins of Phytophthora and studied their suitability for expressing transgenes in P. infestans. Phytophthora spp. encode a standard complement of 79 cytoplasmic ribosomal proteins. Several genes are duplicated, and two appear to be pseudogenes. Half of the genes are expressed at similar levels during all stages of asexual development, and we discovered that the majority share a novel promoter motif named the PhRiboBox. This sequence is enriched in genes associated with transcription, translation, and DNA replication, including tRNA and rRNA biogenesis. Promoters from the three P. infestans genes encoding ribosomal proteins S9, L10, and L23 and their orthologs from P. capsici were tested for their ability to drive transgenes in stable transformants of P. infestans. Five of the six promoters yielded strong expression of a GUS reporter, but the stability of expression was higher using the P. capsici promoters. With the RPS9 and RPL10 promoters of P. infestans, about half of transformants stopped making GUS over two years of culture, while their P. capsici orthologs conferred stable expression. Since cross-talk between native and transgene loci may trigger gene silencing, we encourage the use of heterologous promoters in transformation studies.
Collapse
Affiliation(s)
- Laetitia Poidevin
- Department of Plant Pathology and Microbiology, University of California, Riverside, California, United States of America
| | - Kalina Andreeva
- Department of Plant Pathology and Microbiology, University of California, Riverside, California, United States of America
| | - Careen Khachatoorian
- Department of Plant Pathology and Microbiology, University of California, Riverside, California, United States of America
| | - Howard S. Judelson
- Department of Plant Pathology and Microbiology, University of California, Riverside, California, United States of America
- * E-mail:
| |
Collapse
|
7
|
Kamoun S, Furzer O, Jones JDG, Judelson HS, Ali GS, Dalio RJD, Roy SG, Schena L, Zambounis A, Panabières F, Cahill D, Ruocco M, Figueiredo A, Chen XR, Hulvey J, Stam R, Lamour K, Gijzen M, Tyler BM, Grünwald NJ, Mukhtar MS, Tomé DFA, Tör M, Van Den Ackerveken G, McDowell J, Daayf F, Fry WE, Lindqvist-Kreuze H, Meijer HJG, Petre B, Ristaino J, Yoshida K, Birch PRJ, Govers F. The Top 10 oomycete pathogens in molecular plant pathology. MOLECULAR PLANT PATHOLOGY 2015; 16:413-34. [PMID: 25178392 PMCID: PMC6638381 DOI: 10.1111/mpp.12190] [Citation(s) in RCA: 464] [Impact Index Per Article: 51.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Oomycetes form a deep lineage of eukaryotic organisms that includes a large number of plant pathogens which threaten natural and managed ecosystems. We undertook a survey to query the community for their ranking of plant-pathogenic oomycete species based on scientific and economic importance. In total, we received 263 votes from 62 scientists in 15 countries for a total of 33 species. The Top 10 species and their ranking are: (1) Phytophthora infestans; (2, tied) Hyaloperonospora arabidopsidis; (2, tied) Phytophthora ramorum; (4) Phytophthora sojae; (5) Phytophthora capsici; (6) Plasmopara viticola; (7) Phytophthora cinnamomi; (8, tied) Phytophthora parasitica; (8, tied) Pythium ultimum; and (10) Albugo candida. This article provides an introduction to these 10 taxa and a snapshot of current research. We hope that the list will serve as a benchmark for future trends in oomycete research.
Collapse
Affiliation(s)
- Sophien Kamoun
- The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, UK
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Xiang Q, Judelson HS. Myb transcription factors and light regulate sporulation in the oomycete Phytophthora infestans. PLoS One 2014; 9:e92086. [PMID: 24704821 PMCID: PMC3976263 DOI: 10.1371/journal.pone.0092086] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 02/17/2014] [Indexed: 01/10/2023] Open
Abstract
Life cycle progression in eukaryotic microbes is often influenced by environment. In the oomycete Phytophthora infestans, which causes late blight on potato and tomato, sporangia have been reported to form mostly at night. By growing P. infestans under different light regimes at constant temperature and humidity, we show that light contributes to the natural pattern of sporulation by delaying sporulation until the following dark period. However, illumination does not permanently block sporulation or strongly affect the total number of sporangia that ultimately form. Based on measurements of sporulation-induced genes such as those encoding protein kinase Pks1 and Myb transcription factors Myb2R1 and Myb2R3, it appears that most spore-associated transcripts start to rise four to eight hours before sporangia appear. Their mRNA levels oscillate with the light/dark cycle and increase with the amount of sporangia. An exception to this pattern of expression is Myb2R4, which is induced several hours before the other genes and declines after cultures start to sporulate. Transformants over-expressing Myb2R4 produce twice the number of sporangia and ten-fold higher levels of Myb2R1 mRNA than wild-type, and chromatin immunoprecipitation showed that Myb2R4 binds the Myb2R1 promoter in vivo. Myb2R4 thus appears to be an early regulator of sporulation. We attempted to silence eight Myb genes by DNA-directed RNAi, but succeeded only with Myb2R3, which resulted in suppressed sporulation. Ectopic expression studies of seven Myb genes revealed that over-expression frequently impaired vegetative growth, and in the case of Myb3R6 interfered with sporangia dormancy. We observed that the degree of silencing induced by a hairpin construct was correlated with its copy number, and ectopic expression was often unstable due to epigenetic silencing and transgene excision.
Collapse
Affiliation(s)
- Qijun Xiang
- Department of Plant Pathology and Microbiology, University of California Riverside, Riverside, California, United States of America
| | - Howard S. Judelson
- Department of Plant Pathology and Microbiology, University of California Riverside, Riverside, California, United States of America
| |
Collapse
|
9
|
van West P, Shepherd SJ, Walker CA, Li S, Appiah AA, Grenville-Briggs LJ, Govers F, Gow NAR. Internuclear gene silencing in Phytophthora infestans is established through chromatin remodelling. Microbiology (Reading) 2008; 154:1482-1490. [DOI: 10.1099/mic.0.2007/015545-0] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Pieter van West
- Aberdeen Oomycete Group, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK
| | - Samantha J. Shepherd
- Aberdeen Oomycete Group, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK
| | - Claire A. Walker
- Aberdeen Oomycete Group, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK
| | - Shuang Li
- Aberdeen Oomycete Group, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK
| | - Alex A. Appiah
- Aberdeen Oomycete Group, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK
| | - Laura J. Grenville-Briggs
- Aberdeen Oomycete Group, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK
| | - Francine Govers
- Laboratory of Phytopathology, Binnenhaven 5, 6709 PD Wageningen, The Netherlands
| | - Neil A. R. Gow
- Aberdeen Oomycete Group, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK
| |
Collapse
|
10
|
Gaulin E, Haget N, Khatib M, Herbert C, Rickauer M, Bottin A. Transgenic sequences are frequently lost in Phytophthora parasitica transformants without reversion of the transgene-induced silenced state. Can J Microbiol 2007; 53:152-7. [PMID: 17496962 DOI: 10.1139/w06-090] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Little data exist on the mechanism and stability of transformation in Phytophthora parasitica, a major oomycete parasite of plants. Here, we studied the stability of drug-resistant protoplast transformants by analyzing single-zoospore derivatives. We show that the transgenic sequences are not stably integrated into the chromosomes, resulting in the loss of drug resistance in single-zoospore derivatives. However, in strains where the P. parasitica gene encoding the CBEL elicitor was silenced by transformation with sense or antisense constructs, silencing is not reversed when the transgenic sequences are lost. This suggests that instability of P. parasitica transformants is not an obstacle for loss-of-function studies in this organism.
Collapse
Affiliation(s)
- Elodie Gaulin
- UMR5546 CNRS-Université Paul Sabatier, Castanet-Tolosan, France
| | | | | | | | | | | |
Collapse
|
11
|
Judelson HS, Tani S. Transgene-induced silencing of the zoosporogenesis-specific NIFC gene cluster of Phytophthora infestans involves chromatin alterations. EUKARYOTIC CELL 2007; 6:1200-9. [PMID: 17483289 PMCID: PMC1951104 DOI: 10.1128/ec.00311-06] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Clustered within the genome of the oomycete phytopathogen Phytophthora infestans are four genes encoding spore-specific nuclear LIM interactor-interacting factors (NIF proteins, a type of transcriptional regulator) that are moderately conserved in DNA sequence. NIFC1, NIFC2, and NIFC3 are zoosporogenesis-induced and grouped within 4 kb, and 20 kb away resides a sporulation-induced form, NIFS. To test the function of the NIFC family, plasmids expressing full-length hairpin constructs of NIFC1 or NIFC2 were stably transformed into P. infestans. This triggered silencing of the cognate gene in about one-third of transformants, and all three NIFC genes were usually cosilenced. However, NIFS escaped silencing despite its high sequence similarity to the NIFC genes. Silencing of the three NIFC genes impaired zoospore cyst germination by 60% but did not affect other aspects of the life cycle. Silencing was transcriptional based on nuclear run-on assays and associated with tighter chromatin packing based on nuclease accessibility experiments. The chromatin alterations extended a few hundred nucleotides beyond the boundaries of the transcribed region of the NIFC cluster and were not associated with increased DNA methylation. A plasmid expressing a short hairpin RNA having sequence similarity only to NIFC1 silenced both that gene and an adjacent member of the gene cluster, likely due to the expansion of a heterochromatic domain from the targeted locus. These data help illuminate the mechanism of silencing in Phytophthora and suggest that caution should be used when interpreting silencing experiments involving closely spaced genes.
Collapse
Affiliation(s)
- Howard S Judelson
- Department of Plant Pathology and Microbiology, University of California, Riverside, Riverside, CA 92521, USA.
| | | |
Collapse
|
12
|
Judelson HS, Narayan R, Fong AMVA, Tani S, Kim KS. Performance of a tetracycline-responsive transactivator system for regulating transgenes in the oomycete Phytophthora infestans. Curr Genet 2007; 51:297-307. [PMID: 17377792 DOI: 10.1007/s00294-007-0125-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2006] [Revised: 02/23/2007] [Accepted: 02/24/2007] [Indexed: 11/27/2022]
Abstract
The oomycete genus Phytophthora includes many important plant pathogens for which extensive genome data exist, but lacking is an inducible expression system to study contributions of their genes to growth and pathogenicity. Here the adaptation of the reverse tetracycline transactivator (rtTA) system to P. infestans is described. Vectors were developed containing rtTA expressed from an oomycete promoter, and beta-glucuronidase (GUS) controlled by TetR binding sites fused to a minimal oomycete promoter. Transformants were obtained in which GUS was expressed in a dose-dependent manner by the rtTA inducer doxycycline, indicating that the gene switch functions in P. infestans. However, toxicity of rtTA hindered the isolation of transformants if expressed on the same plasmid as the nptII selection marker. Better results were obtained by cotransforming those genes on separate plasmids, with 92% of transformants acquiring both DNAs although only 4% expressed rtTA at detectable levels. Low levels of reporter activity were measured in such transformants, suggesting that rtTA activated transcription weakly. Also, significant variation in the sensitivity of isolates to doxycycline and tetracycline was observed. These results are useful both in terms of developing tools for functional genomics and understanding the fate of DNA during Phytophthora transformation.
Collapse
Affiliation(s)
- Howard S Judelson
- Department of Plant Pathology, University of California, Riverside, CA 92521, USA.
| | | | | | | | | |
Collapse
|
13
|
Tani S, Judelson H. Activation of zoosporogenesis-specific genes in Phytophthora infestans involves a 7-nucleotide promoter motif and cold-induced membrane rigidity. EUKARYOTIC CELL 2006; 5:745-52. [PMID: 16607021 PMCID: PMC1459674 DOI: 10.1128/ec.5.4.745-752.2006] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Infections of plants by the oomycete Phytophthora infestans typically result from zoospores, which develop from sporangia at cold temperatures. To help understand the relevant cold-induced signaling pathway, factors regulating the transcription of the zoosporogenesis-specific NIF (nuclear LIM-interactor-interacting factor) gene family were examined. Sequences required for inducing PinifC3 were identified by analyzing truncated and mutated promoters using the beta-glucuronidase reporter in stable transformants. A 7-nucleotide (nt) sequence located 139 bases upstream of the major transcription start point (GGACGAG) proved essential for the induction of PinifC3 when sporangia were shifted from ambient to cold temperatures. The motif, named the cold box, also conferred cold inducibility to a promoter normally activated only during sexual development. An identical motif was detected in the two other zoosporogenesis-specific NIF genes from P. infestans and three Phytophthora sojae orthologues, and a closely related sequence was found in Phytophthora ramorum orthologues. The 7-nt motif was also found in the promoters of other zoosporogenesis-induced genes. The presence of a cold box-interacting protein in nuclear extracts of P. infestans sporangia was demonstrated using electrophoretic mobility shift assays. Furthermore, zoospore release and cold box-regulated transcription were stimulated by the membrane rigidizer dimethyl sulfoxide and inhibited by the membrane fluidizer benzyl alcohol. The data therefore delineate a pathway in which sporangia perceive cold temperatures through membrane rigidity, which activates signals that drive both zoosporogenesis and cold-box-mediated transcription.
Collapse
Affiliation(s)
- Shuji Tani
- Department of Plant Pathology, University of California, Riverside, CA 92521, USA
| | | |
Collapse
|
14
|
Hamada W, Soulié MC, Malfatti P, Bompeix G, Boccara M. Stability and modulated expression of a hygromycin resistance gene integrated in Botrytis cinerea transformants. FEMS Microbiol Lett 2006. [DOI: 10.1111/j.1574-6968.1997.tb12642.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
|
15
|
Blanco FA, Judelson HS. A bZIP transcription factor from Phytophthora interacts with a protein kinase and is required for zoospore motility and plant infection. Mol Microbiol 2005; 56:638-48. [PMID: 15819621 DOI: 10.1111/j.1365-2958.2005.04575.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Zoospores are critical in the disease cycle of Phytophthora infestans, a member of the oomycete group of fungus-like microbes and the cause of potato late blight. A protein kinase induced during zoosporogenesis, Pipkz1, was shown to interact in the yeast two-hybrid system with a putative bZIP transcription factor. This interaction was confirmed in vitro using a pull-down assay. The transcription factor gene, Pibzp1, was single copy and expressed in all tissues. Transformants of P. infestans stably silenced for Pibzp1 were generated using plasmids expressing its coding region in sense or antisense orientations. A protoplast transformation method induced silencing more efficiently than transformation by an electroporation scheme. Wild-type and silenced strains exhibited no differences in hyphal growth or morphology, mating, sporangia production or zoospore release. However, zoospores from the mutants spun in tight circles, instead of exhibiting the normal pattern of straight swimming punctuated by turns. Zoospore encystment was unaffected by silencing, but cysts germinated more efficiently than controls. Germinated cysts from the mutants failed to develop appressoria and were unable to infect plants; however, they could colonize wounded tissue. These phenotypes indicate that Pibzp1 is a key regulator of several stages of the zoospore-mediated infection pathway.
Collapse
Affiliation(s)
- Flavio A Blanco
- Center for Plant Cell Biology and Department of Plant Pathology, University of California, Riverside, CA 92521, USA
| | | |
Collapse
|
16
|
Vijn I, Govers F. Agrobacterium tumefaciens mediated transformation of the oomycete plant pathogen Phytophthora infestans. MOLECULAR PLANT PATHOLOGY 2003; 4:459-467. [PMID: 20569405 DOI: 10.1046/j.1364-3703.2003.00191.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
SUMMARY Agrobacterium tumefaciens is widely used for plant DNA transformation and, more recently, has also been used to transform yeast and filamentous fungi. Here we present a protocol for Agrobacterium-mediated DNA transformation of the oomycete Phytophthora infestans, the causal agent of potato late blight. Binary T-DNA vectors containing neomycin phosphotransferase (npt) and beta-glucuronidase (gus) fused to oomycete transcriptional regulatory sequences were constructed. Seven days of co-cultivation followed by transfer to a selective medium containing cefotaxim to kill Agrobacterium and geneticin to select for transformants, resulted in geneticin resistant colonies. Under optimal conditions with Agrobacterium supplemented with a ternary plasmid carrying a constitutive virG gene and in the presence of acetosyringone as inducer, up to 30 transformants per 10(7) zoospores could be obtained. The majority of these transformants contained a single T-DNA copy randomly integrated at a chromosomal locus. Using a similar protocol, geneticin resistant transformants of two other oomycetes species were obtained, Phytophthora palmivora and Pythium ultimum.
Collapse
Affiliation(s)
- Irma Vijn
- Laboratory of Phytopathology, Wageningen University, and Graduate School Experimental Plant Sciences, Binnenhaven 5, NL-6709 PD Wageningen, the Netherlands
| | | |
Collapse
|
17
|
Cvitanich C, Judelson HS. Stable transformation of the oomycete, Phytophthora infestans, using microprojectile bombardment. Curr Genet 2003; 42:228-35. [PMID: 12589474 DOI: 10.1007/s00294-002-0354-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2002] [Revised: 09/19/2002] [Accepted: 09/28/2002] [Indexed: 10/25/2022]
Abstract
Germinated asexual sporangia, zoospores, and mycelia of Phytophthora infestans were transformed to G418-resistance by microprojectile bombardment. After optimization, an average of 14 transformants/shot were obtained, using 10(6) germinated sporangia and gold particles coated with 1 microg of vector. Transformants displayed tandem or simple insertions of vector sequences within chromosomes. Most primary transformants were heterokaryons of transformed and wild-type nuclei, a state which generally persisted for generations, even with G418 selection. Transgenic homokaryons were easily obtained from primary transformants through G418 selection of zoospores. To facilitate the optimization of transformation, experiments were performed using a vector containing neomycin phosphotransferase (npt) and beta-glucuronidase (GUS) genes fused to oomycete transcriptional regulatory sequences. To indicate which orientations of transgenes would maximize their expression, head-to-head, head-to-tail, or tail-to-tail orientations of npt and GUS were compared. Each yielded similar rates of transformation and levels of GUS activity, indicating little transcriptional interference.
Collapse
Affiliation(s)
- Cristina Cvitanich
- Department of Plant Pathology, University of California, Riverside, CA 92521, USA
| | | |
Collapse
|
18
|
Challen MP, Zhang C, Elliott TJ. Agaricus bisporus and Coprinus bilanatus TRP2 genes are tri-functional with conserved intron and domain organisations. FEMS Microbiol Lett 2002; 208:269-74. [PMID: 11959448 DOI: 10.1111/j.1574-6968.2002.tb11093.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Cloned homobasidiomycete TRP2 genes for Agaricus bisporus and Coprinus bilanatus were sequence-characterised. Both genes encode tri-functional proteins with activity domains for glutamine amidotransferase (GAT; G domain), indole glycerol phosphate synthase (InGP; C domain) and phosphoribosyl anthranilate isomerase (F domain). A conserved intron disrupts the GAT-coding sequence in both genes. Consensus amino acid (aa) signatures were identified for GAT and InGP, but in the latter 15-aa signature, one residue did not fit the previously defined consensus. Protein architecture and parsimony analysis with analogous proteins indicate domain organisation (NH(2)-G-C-F-COOH) was as for other filamentous fungi. The data do not support earlier suggestions that the three activity domains are detached in A. bisporus.
Collapse
Affiliation(s)
- Michael P Challen
- Horticulture Research International, Wellesbourne, Warwickshire CV35 9EF, UK.
| | | | | |
Collapse
|
19
|
Judelson HS, Tooley PW. Enhanced Polymerase Chain Reaction Methods for Detecting and Quantifying Phytophthora infestans in Plants. PHYTOPATHOLOGY 2000; 90:1112-1119. [PMID: 18944474 DOI: 10.1094/phyto.2000.90.10.1112] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
ABSTRACT Sensitive and specific primer sets for polymerase chain reaction (PCR) for Phytophthora infestans, the oomycete that causes late blight of potato and tomato, were developed based on families of highly repeated DNA. The performance of these primers was compared to those developed previously for the internal transcribed spacer (ITS) of ribosomal DNA. The detection limit using the new primers is 10 fg of P. infestans DNA, or 0.02 nuclei. This is about 100 times more sensitive than ITS-directed primers. Nested polymerase chain reaction (PCR) allows the measurement of down to 0.1 fg of DNA using the new primers. To enhance the reliability of diagnostic assays, an internal positive control was developed using an amplification mimic. The mimic also served as a competitor for quantitative PCR, which was used to assess the growth of P. infestans in resistant and susceptible tomato. A key dimension of this study was that two laboratories independently checked the specificity and sensitivity of each primer set; differences were noted that should be considered when PCR is adopted for diagnostic applications in any system.
Collapse
|
20
|
Randall TA, Judelson HS. Construction of a bacterial artificial chromosome library of Phytophthora infestans and transformation of clones into P. infestans. Fungal Genet Biol 1999; 28:160-70. [PMID: 10669582 DOI: 10.1006/fgbi.1999.1170] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A bacterial artificial chromosome (BAC) library of Phytophthora infestans was constructed in a derivative of pBELOBACII that had been modified by adding a npt selectable marker gene for transforming P. infestans. A total library of 8 genome equivalents was generated and 16,128 clones with inserts averaging 75 kb (4.9 genome equivalents) were individually picked and stored as an arrayed library in microtiter plates. This coverage was confirmed by screening the library for 11 DNA loci by colony hybridization and by polymerase chain reaction of DNA pools. Transformation of P. infestans with BAC clones containing inserts of 93 to 135 kb was demonstrated. The efficiency of transformation with most BACs was noticeably higher than that with smaller plasmids. Detailed analyses of transformants obtained with a 102-kb BAC indicated that entire inserts were present in about one-quarter of the transformants.
Collapse
Affiliation(s)
- T A Randall
- Department of Plant Pathology, University of California at Riverside, Riverside, California 92521, USA
| | | |
Collapse
|
21
|
Tetley L, Brown SMA, McDonald V, Coombs GH. Heterologous expression of a basic elicitin from Phytophthora cryptogea in Phytophthora infestans increases its ability to cause leaf necrosis in tobacco. MICROBIOLOGY (READING, ENGLAND) 1998; 144 ( Pt 12):3343-3349. [PMID: 9884226 DOI: 10.1099/00221287-144-12-3343] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The cry-b sequence, encoding a basic elicitin (cryptogein B) from Phytophthora cryptogea, was co-transformed into Phytophthora infestans. The copy number of the cry-b sequence varied in co-transformants. Nevertheless, in all cases the alien elicitin gene was transcribed, translated and the protein secreted in vitro from such transformants. Moreover, the secreted cryptogein B from P. infestans co-transformants increased their ability to cause a hypersensitive-response-like necrosis of tobacco leaves. It was thus concluded that the transfer of a single gene encoding a basic elicitin from one Phytophthora species to another can dramatically alter the phenotypic interaction of the transformed species with tobacco.
Collapse
Affiliation(s)
- Laurence Tetley
- Division of Infection and Immunity, Institute of Biomedical and Life Sciences, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, UK
| | - Samantha M A Brown
- Division of Infection and Immunity, Institute of Biomedical and Life Sciences, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, UK
| | - Vincent McDonald
- Department of Clinical Sciences, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Graham H Coombs
- Division of Infection and Immunity, Institute of Biomedical and Life Sciences, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, UK
| |
Collapse
|
22
|
Judelson HS. The genetics and biology of Phytophthora infestans: modern approaches to a historical challenge. Fungal Genet Biol 1997; 22:65-76. [PMID: 9367653 DOI: 10.1006/fgbi.1997.1006] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The oomyceteous fungus Phytophthora infestans, which causes the late blight diseases of potato and tomato, has a history that is closely associated with that of mycology and plant pathology. Nevertheless, P. infestans and other oomycetes remain poorly understood relative to fungi in other groups. A resurgence in the worldwide impact of late blight has recently increased interest in the species. Fortunately, over the past decade improved tools for laboratory analysis have been developed which provide an opportunity to advance our understanding of this important pathogen. Since oomycetes do not have a close taxonomic affinity with well-characterized organisms such as ascomycetes and basidiomycetes, it is likely that studies of P. infestans will yield novel biological findings. This review provides an update on the status of research into the fundamental aspects of the biology, genetics, and pathology of P. infestans and describes prospects for future advances.
Collapse
Affiliation(s)
- H S Judelson
- Department of Plant Pathology, University of California, Riverside, California, 92521, USA
| |
Collapse
|
23
|
Smith ML, Yang CJ, Metzenberg RL, Glass NL. Escape from het-6 incompatibility in Neurospora crassa partial diploids involves preferential deletion within the ectopic segment. Genetics 1996; 144:523-31. [PMID: 8889517 PMCID: PMC1207547 DOI: 10.1093/genetics/144.2.523] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Self-incompatible het-6OR/het-6PA partial diploids of Neurospora crassa were selected from a cross involving the translocation strain, T(IIL-->IIIR)AR18, and a normal sequence strain. About 25% of the partial diploids exhibited a marked increase in growth rate after 2 weeks, indicating that "escape" from het-6 incompatibility had occurred. Near isogenic tester strains with different alleles (het-6OR and het-6PA) were constructed and used to determine that 80 of 96 escape strains tested were het-6PA, retaining the het-6 allele found in the normal-sequence LGII position; 16 were het-6OR, retaining the allele in the translocated position. Restriction fragment length polymorphisms in 45 escape strains were examined with probes made from cosmids that spanned the translocated region. Along with electrophoretic analysis of chromosomes from three escape strains, RFLPs showed that escape is associated with deletion of part of one or the other of the duplicated DNA segments. Deletions ranged in size from approximately 70 kbp up to putatively the entire 270-kbp translocated region but always included a 35-kbp region wherein we hypothesize het-6 is located. The deletion spectrum at het-6 thus resembles other cases where mitotic deletions occur such as of tumor suppressor genes and of the hprt gene (coding for hypoxanthine-guanine phosphoribosyl-transferase) in humans.
Collapse
Affiliation(s)
- M L Smith
- Biology Department, Carleton University, Ottawa, Ontario, Canada.
| | | | | | | |
Collapse
|
24
|
Schmidt-Kastner PK, Jardine K, Cormier M, McBurney MW. Genes transfected into embryonal carcinoma stem cells are both lost and inactivated at high frequency. SOMATIC CELL AND MOLECULAR GENETICS 1996; 22:383-92. [PMID: 9039847 DOI: 10.1007/bf02369894] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Embryonal carcinoma (EC) cells can be efficiently transfected with cloned DNAs but there is a strong tendency for expression from transfected genes to be lost from stably transformed cells. To investigate the mechanism responsible for this loss of expression, we transfected P19 EC cells with a gene encoding the E. coli beta-galactosidase and examined expression of this gene in clonal populations of cells. Cells that carry and express the beta-galactosidase gene give rise to cells that do not express at a rate of about 0.02 events per cell per cell division. These non-expressing cells were of two types, some had lost the transfected genes while others had inactivated them. In those cells that retained but inactivated the transfected genes, the inactive state was stable and suppression was at the level of transcription initiation but not associated with increased DNA methylation. Because transfected DNAs integrate into the genome as tandem arrays, the gene loss and inactivation seen in EC cells may be analogous to the repeat-induced gene inactivation seen in lower eukaryotes.
Collapse
|