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Laloum Y, Gangneux C, Gügi B, Lanoue A, Munsch T, Blum A, Gauthier A, Trinsoutrot-Gattin I, Boulogne I, Vicré M, Driouich A, Laval K, Follet-Gueye ML. Faba bean root exudates alter pea root colonization by the oomycete Aphanomyces euteiches at early stages of infection. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2021; 312:111032. [PMID: 34620436 DOI: 10.1016/j.plantsci.2021.111032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 07/14/2021] [Accepted: 08/20/2021] [Indexed: 06/13/2023]
Abstract
Aphanomyces euteiches is an oomycete pathogen that causes the pea root rot. We investigated the potential role of early belowground defense in pea (susceptible plant) and faba bean (tolerant plant) at three days after inoculation. Pea and faba bean were inoculated with A. euteiches zoospores. Root colonization was examined. Root exudates from pea and faba bean were harvested and their impact on A. euteiches development were assessed by using in vitro assays. A. euteiches root colonization and the influence of the oomycete inoculation on specialized metabolites patterns and arabinogalactan protein (AGP) concentration of root exudates were also determined. In faba bean root, A. euteiches colonization was very low as compared with that of pea. Whereas infected pea root exudates have a positive chemotaxis index (CI) on zoospores, faba bean exudate CI was negative suggesting a repellent effect. While furanoacetylenic compounds were only detected in faba bean exudates, AGP concentration was specifically increased in pea.This work showed that early in the course of infection, host susceptibility to A. euteiches is involved via a plant-species specific root exudation opening new perspectives in pea root rot disease management.
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Affiliation(s)
- Yohana Laloum
- AGHYLE research unit, UP 2018.C101, UniLaSalle Rouen 3 rue du tronquet CS 40118, 76134, Mont Saint Aignan, France; Normandie Univ, UNIROUEN, Glyco-MEV, EA4358, SFR NORVEGE FED 4277, I2C Carnot, IRIB, 76000, Rouen, France
| | - Christophe Gangneux
- AGHYLE research unit, UP 2018.C101, UniLaSalle Rouen 3 rue du tronquet CS 40118, 76134, Mont Saint Aignan, France
| | - Bruno Gügi
- Normandie Univ, UNIROUEN, Glyco-MEV, EA4358, SFR NORVEGE FED 4277, I2C Carnot, IRIB, 76000, Rouen, France
| | - Arnaud Lanoue
- Université de Tours, EA 2106 «Biomolécules et Biotechnologies Végétales», UFR des Sciences Pharmaceutiques, 31 Av. Monge, F37200, Tours, France
| | - Thibaut Munsch
- Université de Tours, EA 2106 «Biomolécules et Biotechnologies Végétales», UFR des Sciences Pharmaceutiques, 31 Av. Monge, F37200, Tours, France
| | - Adrien Blum
- AGHYLE research unit, UP 2018.C101, UniLaSalle Rouen 3 rue du tronquet CS 40118, 76134, Mont Saint Aignan, France
| | - Adrien Gauthier
- AGHYLE research unit, UP 2018.C101, UniLaSalle Rouen 3 rue du tronquet CS 40118, 76134, Mont Saint Aignan, France
| | - Isabelle Trinsoutrot-Gattin
- AGHYLE research unit, UP 2018.C101, UniLaSalle Rouen 3 rue du tronquet CS 40118, 76134, Mont Saint Aignan, France
| | - Isabelle Boulogne
- Normandie Univ, UNIROUEN, Glyco-MEV, EA4358, SFR NORVEGE FED 4277, I2C Carnot, IRIB, 76000, Rouen, France
| | - Maïté Vicré
- Normandie Univ, UNIROUEN, Glyco-MEV, EA4358, SFR NORVEGE FED 4277, I2C Carnot, IRIB, 76000, Rouen, France
| | - Azeddine Driouich
- Normandie Univ, UNIROUEN, Glyco-MEV, EA4358, SFR NORVEGE FED 4277, I2C Carnot, IRIB, 76000, Rouen, France
| | - Karine Laval
- AGHYLE research unit, UP 2018.C101, UniLaSalle Rouen 3 rue du tronquet CS 40118, 76134, Mont Saint Aignan, France
| | - Marie-Laure Follet-Gueye
- Normandie Univ, UNIROUEN, Glyco-MEV, EA4358, SFR NORVEGE FED 4277, I2C Carnot, IRIB, 76000, Rouen, France.
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2
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Jiang H, Hwang HW, Ge T, Cole B, Perkins B, Hao J. Leucine Regulates Zoosporic Germination and Infection by Phytophthora erythroseptica. Front Microbiol 2019; 10:131. [PMID: 30804912 PMCID: PMC6370700 DOI: 10.3389/fmicb.2019.00131] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 01/21/2019] [Indexed: 11/20/2022] Open
Abstract
Pink rot (Phytophthora erythroseptica) of potato is a major concern in many potato production regions. The pathogen produces zoospores that serve as a primary inoculum for infection. To understand how the pink rot incidence is related to pathogen population, qualitative, and quantitative chemical analyses were conducted. It was demonstrated that P. erythroseptica zoospores required a minimal population of 103 zoospores/ml (threshold) for initiating germination and the subsequent infection; the percentage of zoosporic germination was positively correlated with the density of zoospores above the threshold. To elucidate the density-dependent behavior, zoospore exudate (ZE) was extracted from high-density (105/ml) zoospore suspension. Zoosporic inocula of P. erythroseptica at different concentrations were inoculated on potato tubers. Necrotic lesions were caused by inoculum with 100 zoospores per inoculation site; 5 zoospores per site did not cause lesions on the tuber. However, five zoospores did cause lesions when they were placed in ZE, suggesting ZE contained chemical compounds that regulate germination of zoospores. ZE was collected and analyzed using liquid chromatography mass spectroscopy (LC-MS). Results showed that the amino acid leucine was associated with zoosporic germination. Therefore, zoosporic germination and infection of P. erythroseptica were mediated by signaling molecules secreted from zoospores.
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Affiliation(s)
- He Jiang
- School of Food and Agriculture, The University of Maine, Orono, ME, United States
| | - Hye Weon Hwang
- Department of Chemistry, The University of Maine, Orono, ME, United States
| | - Tongling Ge
- School of Food and Agriculture, The University of Maine, Orono, ME, United States
| | - Barbara Cole
- Department of Chemistry, The University of Maine, Orono, ME, United States
| | - Brian Perkins
- School of Food and Agriculture, The University of Maine, Orono, ME, United States
| | - Jianjun Hao
- School of Food and Agriculture, The University of Maine, Orono, ME, United States
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3
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Affiliation(s)
- Chang Xu
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, 43403-0212
| | - Paul F. Morris
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, 43403-0212
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Khatun A, Farhana T, Sabir AA, Islam SMN, West HM, Rahman M, Islam T. Pseudomonas and Burkholderia inhibit growth and asexual development of Phytophthora capsici. ACTA ACUST UNITED AC 2018; 73:123-135. [DOI: 10.1515/znc-2017-0065] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2017] [Accepted: 12/18/2017] [Indexed: 11/15/2022]
Abstract
Abstract
The objective of this study was to isolate and characterize antagonistic rhizobacteria from chili against a notorious phytopathogen Phytophthora capsici. Among the 48 bacteria isolated, BTLbbc-02, BTLbbc-03, and BTLbbc-05 were selected based on their inhibitory activity against P. capsici. They were tentatively identified as Burkholderia metallica BTLbbc-02, Burkholderia cepacia BTLbbc-03, and Pseudomonas aeruginosa BTLbbc-05, respectively, based on their 16S rRNA gene sequencing. All inhibited the growth of P. capsici at varying levels by inducing characteristic morphological alterations of P. capsici hyphae. The cell-free culture supernatant of all three isolates impaired motility (up to 100%) and caused lysis (up to 50%) of the halted zoospores. Bioassays revealed that Pseudomonas sp. had higher antagonism and zoospore motility-inhibitory effects against P. capsici compared with two other isolates, Burkholderia spp. and B. metallica, which caused vacuolation in mycelium. All three bacteria suppressed sporangium formation and zoosporogenesis of P. capsici, and improved the seed germination and growth of cucumber. Our findings suggest that epiphytic bacteria, B. metallica, B. cepacia, and P. aeruginosa, could be used as potential biocontrol agents against P. capsici. A further study is required to ensure conformity with the existing regulations for soil, plant, and human health.
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Affiliation(s)
- Amena Khatun
- Department of Biotechnology , Bangabandhu Sheikh Mujibur Rahman Agricultural University , Gazipur 1706 , Bangladesh
| | - Tarin Farhana
- Department of Biotechnology , Bangabandhu Sheikh Mujibur Rahman Agricultural University , Gazipur 1706 , Bangladesh
| | - Abdullah As Sabir
- Department of Biotechnology , Bangabandhu Sheikh Mujibur Rahman Agricultural University , Gazipur 1706 , Bangladesh
| | - Shah Mohammad Naimul Islam
- Department of Biotechnology , Bangabandhu Sheikh Mujibur Rahman Agricultural University , Gazipur 1706 , Bangladesh
| | - Helen M. West
- School of Biosciences , University of Nottingham , Loughborough , UK
| | - Mahfuzur Rahman
- Extension Service , West Virginia University , Morgantown, WV 26506 , USA
| | - Tofazzal Islam
- Department of Biotechnology , Bangabandhu Sheikh Mujibur Rahman Agricultural University , Gazipur 1706 , Bangladesh
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Rezinciuc S, Sandoval-Sierra JV, Ruiz-León Y, van West P, Diéguez-Uribeondo J. Specialized attachment structure of the fish pathogenic oomycete Saprolegnia parasitica. PLoS One 2018; 13:e0190361. [PMID: 29342156 PMCID: PMC5771568 DOI: 10.1371/journal.pone.0190361] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 12/13/2017] [Indexed: 12/18/2022] Open
Abstract
The secondary cysts of the fish pathogen oomycete Saprolegnia parasitica possess bundles of long hooked hairs that are characteristic to this economically important pathogenic species. Few studies have been carried out on elucidating their specific role in the S. parasitica life cycle and the role they may have in the infection process. We show here their function by employing several strategies that focus on descriptive, developmental and predictive approaches. The strength of attachment of the secondary cysts of this pathogen was compared to other closely related species where bundles of long hooked hairs are absent. We found that the attachment of the S. parasitica cysts was around three times stronger than that of other species. The time sequence and influence of selected factors on morphology and the number of the bundles of long hooked hairs conducted by scanning electron microscopy study revealed that these are dynamic structures. They are deployed early after encystment, i.e., within 30 sec of zoospore encystment, and the length, but not the number, of the bundles steadily increased over the encystment period. We also observed that the number and length of the bundles was influenced by the type of substrate and encystment treatment applied, suggesting that these structures can adapt to different substrates (glass or fish scales) and can be modulated by different signals (i.e., protein media, 50 mM CaCl2 concentrations, carbon particles). Immunolocalization studies evidenced the presence of an adhesive extracellular matrix. The bioinformatic analyses of the S. parasitica secreted proteins showed that there is a high expression of genes encoding domains of putative proteins related to the attachment process and cell adhesion (fibronectin and thrombospondin) coinciding with the deployment stage of the bundles of long hooked hairs formation. This suggests that the bundles are structures that might contribute to the adhesion of the cysts to the host because they are composed of these adhesive proteins and/or by increasing the surface of attachment of this extracellular matrix.
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Affiliation(s)
| | | | | | - Pieter van West
- International Centre for Aquaculture Research and Development at the University of Aberdeen, Aberdeen Oomycete Laboratory, Institute of Medical Sciences, Foresterhill, Aberdeen, United Kingdom
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6
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Kong P, Hong C. Soil bacteria as sources of virulence signal providers promoting plant infection by Phytophthora pathogens. Sci Rep 2016; 6:33239. [PMID: 27616267 PMCID: PMC5018965 DOI: 10.1038/srep33239] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Accepted: 08/22/2016] [Indexed: 11/08/2022] Open
Abstract
Phytophthora species are known as "plant destroyers" capable of initiating single zoospore infection in the presence of a quorum of chemical signals from the same or closely related species of oomycetes. Since the natural oomycete population is too low to reach a quorum necessary to initiate a disease epidemic, creation of the quorum is reliant on alternate sources. Here, we show that a soil bacterial isolate, Bacillus megaterium Sb5, promotes plant infection by Phytophthora species. In the presence of Sb5 exudates, colonization of rhododendron leaf discs by 12 Phytophthora species/isolates was significantly enhanced, single zoospores of P. nicotianae infected annual vinca and P. sojae race 25 successfully attacked a non-host plant, Nicotiana benthamiana as well as resistant soybean cultivars with RPS1a or RPS3a. Sb5 exudates, most notably the fractions larger than 3 kDa, promoted plant infection by improving zoospore swimming, germination and plant attachment. Sb5 exudates also stimulated infection hypha growth and upregulated effector gene expression. These results suggest that environmental bacteria are important sources of virulence signal providers that promote plant infection by Phytophthora species, advancing our understanding of biotic factors in the environmental component of the Phytophthora disease triangle and of communal infection of plant pathogens.
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Affiliation(s)
- Ping Kong
- Hampton Roads Agricultural Research and Extension Center, Virginia Tech, 1444 Diamond Springs Road, Virginia Beach, VA 23455, USA
| | - Chuanxue Hong
- Hampton Roads Agricultural Research and Extension Center, Virginia Tech, 1444 Diamond Springs Road, Virginia Beach, VA 23455, USA
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Crocker EV, Karp MA, Nelson EB. Virulence of oomycete pathogens from Phragmites australis-invaded and noninvaded soils to seedlings of wetland plant species. Ecol Evol 2015; 5:2127-39. [PMID: 26078850 PMCID: PMC4461415 DOI: 10.1002/ece3.1468] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Revised: 02/13/2015] [Accepted: 02/16/2015] [Indexed: 12/17/2022] Open
Abstract
Soil pathogens affect plant community structure and function through negative plant-soil feedbacks that may contribute to the invasiveness of non-native plant species. Our understanding of these pathogen-induced soil feedbacks has relied largely on observations of the collective impact of the soil biota on plant populations, with few observations of accompanying changes in populations of specific soil pathogens and their impacts on invasive and noninvasive species. As a result, the roles of specific soil pathogens in plant invasions remain unknown. In this study, we examine the diversity and virulence of soil oomycete pathogens in freshwater wetland soils invaded by non-native Phragmites australis (European common reed) to better understand the potential for soil pathogen communities to impact a range of native and non-native species and influence invasiveness. We isolated oomycetes from four sites over a 2-year period, collecting nearly 500 isolates belonging to 36 different species. These sites were dominated by species of Pythium, many of which decreased seedling survival of a range of native and invasive plants. Despite any clear host specialization, many of the Pythium species were differentially virulent to the native and non-native plant species tested. Isolates from invaded and noninvaded soils were equally virulent to given individual plant species, and no apparent differences in susceptibility were observed between the collective groups of native and non-native plant species.
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Affiliation(s)
- Ellen V Crocker
- Forest Health Research and Education Center, Department of Forestry, University of Kentucky Lexington, Kentucky, 40503
| | - Mary Ann Karp
- School of Integrative Plant Science, Section of Plant Pathology and Plant-Microbe Biology, Cornell University Ithaca, New York, 14853
| | - Eric B Nelson
- School of Integrative Plant Science, Section of Plant Pathology and Plant-Microbe Biology, Cornell University Ithaca, New York, 14853
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8
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Kong P, Hong C. Oxygen stress reduces zoospore survival of Phytophthora species in a simulated aquatic system. BMC Microbiol 2014; 14:124. [PMID: 24885900 PMCID: PMC4028286 DOI: 10.1186/1471-2180-14-124] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 04/30/2014] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND The genus Phytophthora includes a group of agriculturally important pathogens and they are commonly regarded as water molds. They produce motile zoospores that can move via water currents and on their own locomotion in aquatic environments. However, zoosporic response to dissolved oxygen, an important water quality parameter, is not known. Like other water quality parameters, dissolved oxygen concentration in irrigation reservoirs fluctuates dramatically over time. The aim of this study was to determine whether and how zoospore survival may be affected by elevated and low concentrations of dissolved oxygen in water to better understand the aquatic biology of these pathogens in irrigation reservoirs. RESULTS Zoospores of P. megasperma, P. nicotianae, P. pini and P. tropicalis were assessed for survival in 10% Hoagland's solution at a range of dissolved concentrations from 0.9 to 20.1 mg L(-1) for up to seven exposure times from 0 to 72 h. Zoospore survival was measured by resultant colony counts per ml. Zoospores of these species survived the best in control Hoagland's solution at dissolved oxygen concentrations of 5.3 to 5.6 mg L(-1). Zoospore survival rates decreased with increasing and decreasing concentration of dissolved oxygen, depending upon Phytophthora species and exposure time. Overall, P. megasperma and P. pini are less sensitive than P. nicotianae and P. tropicalis to hyperoxia and hypoxia conditions. CONCLUSION Zoospores in the control solution declined over time and this natural decline process was enhanced under hyperoxia and hypoxia conditions. These findings suggest that dramatic fluctuations of dissolved oxygen in irrigation reservoirs contribute to the population decline of Phytophthora species along the water path in the same reservoirs. These findings advanced our understanding of the aquatic ecology of these pathogens in irrigation reservoirs. They also provided a basis for pathogen risk mitigation by prolonging the turnover time of runoff water in recycling irrigation systems via better system designs.
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Affiliation(s)
- Ping Kong
- Virginia Tech, Hampton Roads Agricultural Research and Extension Center, Virginia Beach, VA 23455, USA
| | - Chuanxue Hong
- Virginia Tech, Hampton Roads Agricultural Research and Extension Center, Virginia Beach, VA 23455, USA
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9
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Savory AIM, Grenville-Briggs LJ, Wawra S, van West P, Davidson FA. Auto-aggregation in zoospores of Phytophthora infestans: the cooperative roles of bioconvection and chemotaxis. J R Soc Interface 2014; 11:20140017. [PMID: 24598206 DOI: 10.1098/rsif.2014.0017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Phytophthora infestans is a highly destructive plant pathogen. It was the cause of the infamous Irish potato famine in the nineteenth century and remains to this day a significant global problem with associated costs estimated at $3 billion annually. Key to the success of this pathogen is the dispersal of free-swimming cells called zoospores. A poorly understood aspect of zoospore behaviour is auto-aggregation--the spontaneous formation of large-scale patterns in cell density. Current competing hypotheses suggest that these patterns are formed by one of two distinct mechanisms: chemotaxis and bioconvection. In this paper, we present mathematical and experimental results that together provide strong evidence that auto-aggregation can only result from a combination of these mechanisms, each having a distinct, time-separated role. A better understanding of the underlying infection mechanisms of P. infestans and potentially other Phytophthora species will in the longer term lead to advances in preventative treatment and thus potentially significant savings in socio-economic costs.
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10
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Carr EA, Nelson EB. Disease-Suppressive Vermicompost Induces a Shift in Germination Mode of Pythium aphanidermatum Zoosporangia. PLANT DISEASE 2014; 98:361-367. [PMID: 30708444 DOI: 10.1094/pdis-05-13-0466-re] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Compost amendments to soils can minimize losses from soilborne plant pathogens, yet the mechanisms by which this occurs have not been well elucidated. In the present study, developmental responses of Pythium aphanidermatum zoosporangia to vermicomposts were observed to better understand how suppression of Pythium seedling disease is expressed. Mature zoosporangia were exposed to vermicompost extracts (VCEs) and monitored using time-lapse photomicroscopy. Sterile and nonsterile VCEs inhibited indirect germination and viable zoospore production whereas zoosporangia germinated directly in VCE to produce germ tubes. Additional treatments were tested to determine factors that promote direct over indirect germination. The pH (5 to 9 at 0.001 M) and ionic strength (0.1 to 0.0001 at pH 6) of potassium phosphate buffer did not alter zoosporogenesis compared with sterile water. Decreasing osmotic potentials in glucose and sucrose from -248 to -2,712 kPa or in polyethylene glycol 8000 from -0.335 to -105 kPa led to a decrease in indirect germination with a corresponding increase in direct germination. Significant levels of seed infection were observed within 1 h of exposure to zoospores (produced in sterile water) or to germ tubes (produced in sucrose solution). Our data demonstrate that VCEs suppress zoosporogenesis and stimulate direct germination; however, this did not result in the suppression of germ tube growth and seed infection.
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Affiliation(s)
- Eric A Carr
- Department of Plant Pathology & Plant-Microbe Biology, Cornell University, Ithaca, NY 14853
| | - Eric B Nelson
- Department of Plant Pathology & Plant-Microbe Biology, Cornell University, Ithaca, NY 14853
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11
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Gunning TK, Conlan XA, Parker RM, Dyson GA, Adams MJ, Barnett NW, Cahill DM. Profiling of secondary metabolites in blue lupin inoculated with Phytophthora cinnamomi following phosphite treatment. FUNCTIONAL PLANT BIOLOGY : FPB 2013; 40:1089-1097. [PMID: 32481177 DOI: 10.1071/fp13023] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 04/19/2013] [Indexed: 06/11/2023]
Abstract
In order to discover phytochemicals that are potentially bioactive against Phytophthora cinnamomi, (a soil-borne plant pathogen) a metabolite profiling protocol for investigation of metabolic changes in Lupinus angustifolius L. plant roots in response to pathogen challenge has been established. Analysis of the metabolic profiles from healthy and P. cinnamomi-inoculated root tissue with high resolution mass spectrometry and nuclear magnetic resonance spectroscopy confirmed that although susceptible, L. angustifolius upregulated a defence associated genistein and 2'-hydroxygenistein-based isoflavonoid and a soyasapogenol saponin at 12h post inoculation which increased in concentration at 72h post inoculation. In contrast to the typical susceptible interaction, the application of a phosphorous-based treatment to L. angustifolius foliage 48h before P. cinnamomi challenge negated the ability of the pathogen to colonise the root tissue and cause disease. Importantly, although the root profiles of water-treated and phosphite-treated plants post pathogen inoculation contained the same secondary metabolites, concentration variations were observed. Accumulation of secondary metabolites within the P. cinnamomi-inoculated plants confirms that pathogen ingress of the root interstitially occurs in phosphite-treated plants, confirming a direct mode of action against the pathogen upon breaching the root cells.
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Affiliation(s)
- Tiffany K Gunning
- Centre for Chemistry and Biotechnology, School of Life and Environmental Sciences, Deakin University, Geelong, Vic. 3217, Australia
| | - Xavier A Conlan
- Centre for Chemistry and Biotechnology, School of Life and Environmental Sciences, Deakin University, Geelong, Vic. 3217, Australia
| | - Rhiannon M Parker
- Applied Chemistry, School of Applied Sciences, RMIT University, Melbourne, Vic. 3001, Australia
| | - Gail A Dyson
- Centre for Chemistry and Biotechnology, School of Life and Environmental Sciences, Deakin University, Geelong, Vic. 3217, Australia
| | - Mike J Adams
- Applied Chemistry, School of Applied Sciences, RMIT University, Melbourne, Vic. 3001, Australia
| | - Neil W Barnett
- Centre for Chemistry and Biotechnology, School of Life and Environmental Sciences, Deakin University, Geelong, Vic. 3217, Australia
| | - David M Cahill
- Centre for Chemistry and Biotechnology, School of Life and Environmental Sciences, Deakin University, Geelong, Vic. 3217, Australia
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12
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13
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Meier IC, Avis PG, Phillips RP. Fungal communities influence root exudation rates in pine seedlings. FEMS Microbiol Ecol 2012; 83:585-95. [PMID: 23013386 DOI: 10.1111/1574-6941.12016] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 09/19/2012] [Accepted: 09/20/2012] [Indexed: 11/27/2022] Open
Abstract
Root exudates are hypothesized to play a central role in belowground food webs, nutrient turnover, and soil C dynamics in forests, but little is known about the extent to which root-associated microbial communities influence exudation rates in trees. We used a novel experimental technique to inoculate loblolly pine (Pinus taeda L.) seedlings with indigenous forest fungi to examine how diverse fungal communities influence exudation. Surface-sterilized seeds were sown in intact, unsieved soil cores for 14 weeks to promote root colonization by fungi. After 14 weeks, we transferred seedlings and root-associated fungi into cuvettes and measured exudate accumulation in trap solutions. Both the abundance and identity of root-associated fungi influenced exudation. Exudation rates were greatest in root systems least colonized by ectomycorrhizal (ECM) fungi and most colonized by putative pathogenic and saprotrophic fungi. However, the ECM community composition was not a strong determinant of exudation rates. These results suggest that environmental conditions that influence the degree to which tree roots are colonized by pathogenic and saprotrophic vs. mutualistic fungi are likely to mediate fluxes of labile C in forest soils, with consequences for soil biogeochemistry and ecosystem processes.
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Affiliation(s)
- Ina C Meier
- Department of Biology, Indiana University, Bloomington, IN, USA.
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Nowicki M, Foolad MR, Nowakowska M, Kozik EU. Potato and Tomato Late Blight Caused by Phytophthora infestans: An Overview of Pathology and Resistance Breeding. PLANT DISEASE 2012; 96:4-17. [PMID: 30731850 DOI: 10.1094/pdis-05-11-0458] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Affiliation(s)
- Marcin Nowicki
- Research Institute of Horticulture, Department of Genetics, Breeding and Biotechnology of Vegetable Plants, Skierniewice, Poland
| | - Majid R Foolad
- Department of Horticulture and The Intercollege Graduate Degree Programs in Plant Biology and Genetics, The Pennsylvania State University, University Park
| | - Marzena Nowakowska
- Research Institute of Horticulture, Department of Genetics, Breeding and Biotechnology of Vegetable Plants, Skierniewice, Poland
| | - Elznieta U Kozik
- Research Institute of Horticulture, Department of Genetics, Breeding and Biotechnology of Vegetable Plants, Skierniewice, Poland
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Judelson HS, Ah-Fong AMV. The kinome of Phytophthora infestans reveals oomycete-specific innovations and links to other taxonomic groups. BMC Genomics 2010; 11:700. [PMID: 21143935 PMCID: PMC3019232 DOI: 10.1186/1471-2164-11-700] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Accepted: 12/09/2010] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Oomycetes are a large group of economically and ecologically important species. Its most notorious member is Phytophthora infestans, the cause of the devastating potato late blight disease. The life cycle of P. infestans involves hyphae which differentiate into spores used for dispersal and host infection. Protein phosphorylation likely plays crucial roles in these stages, and to help understand this we present here a genome-wide analysis of the protein kinases of P. infestans and several relatives. The study also provides new insight into kinase evolution since oomycetes are taxonomically distant from organisms with well-characterized kinomes. RESULTS Bioinformatic searches of the genomes of P. infestans, P. ramorum, and P. sojae reveal they have similar kinomes, which for P. infestans contains 354 eukaryotic protein kinases (ePKs) and 18 atypical kinases (aPKs), equaling 2% of total genes. After refining gene models, most were classifiable into families seen in other eukaryotes. Some ePK families are nevertheless unusual, especially the tyrosine kinase-like (TKL) group which includes large oomycete-specific subfamilies. Also identified were two tyrosine kinases, which are rare in non-metazoans. Several ePKs bear accessory domains not identified previously on kinases, such as cyclin-dependent kinases with integral cyclin domains. Most ePKs lack accessory domains, implying that many are regulated transcriptionally. This was confirmed by mRNA expression-profiling studies that showed that two-thirds vary significantly between hyphae, sporangia, and zoospores. Comparisons to neighboring taxa (apicomplexans, ciliates, diatoms) revealed both clade-specific and conserved features, and multiple connections to plant kinases were observed. The kinome of Hyaloperonospora arabidopsidis, an oomycete with a simpler life cycle than P. infestans, was found to be one-third smaller. Some differences may be attributable to gene clustering, which facilitates subfamily expansion (or loss) through unequal crossing-over. CONCLUSION The large sizes of the Phytophthora kinomes imply that phosphorylation plays major roles in their life cycles. Their kinomes also include many novel ePKs, some specific to oomycetes or shared with neighboring groups. Little experimentation to date has addressed the biological functions of oomycete kinases, but this should be stimulated by the structural, evolutionary, and expression data presented here. This may lead to targets for disease control.
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Affiliation(s)
- Howard S Judelson
- Department of Plant Pathology and Microbiology, University of California, Riverside, California 92521 USA
| | - Audrey MV Ah-Fong
- Department of Plant Pathology and Microbiology, University of California, Riverside, California 92521 USA
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Kong P, Hong C. Zoospore density-dependent behaviors of Phytophthora nicotianae are autoregulated by extracellular products. PHYTOPATHOLOGY 2010; 100:632-637. [PMID: 20528180 DOI: 10.1094/phyto-100-7-0632] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Phytophthora species are destructive fungus-like plant pathogens that use asexual single-celled flagellate zoospores for dispersal and plant infection. Many of the zoospore behaviors are density-dependent although the underlying mechanisms are poorly understood. Here, we use P. nicotianae as a model and demonstrate autoregulation of some zoospore behaviors using signal molecules that zoospores release into the environment. Specifically, zoospore aggregation, plant targeting, and infection required or were enhanced by threshold concentrations of these signal molecules. Below the threshold concentration, zoospores did not aggregate and move toward a cauline leaf of Arabidopsis thaliana (Col-0) and failed to individually attack annual vinca (Catharanthus roseus cv. Little Bright Eye). These processes were reversed when supplemented with zoospore-free fluid (ZFF) prepared from a zoospore suspension above threshold densities but not with calcium chloride at a concentration equivalent to extracellular Ca(2+) in ZFF. These results suggest that Ca(2+) is not a primary signal molecule regulating these communal behaviors. Zoospores coordinated their communal behaviors by releasing, detecting, and responding to signal molecules. This chemical communication mechanism raises the possibility that Phytophthora plant infection may not depend solely on zoospore number in the real world. Single zoospore infection may take place if it is signaled by a common molecule available in the environment which contributes to the destructiveness of these plant pathogens.
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Affiliation(s)
- Ping Kong
- Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, 14444 Diamond Springs Road, Virginia Beach 23455-3363, USA.
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17
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Lioussanne L, Jolicoeur M, St-Arnaud M. Role of the modification in root exudation induced by arbuscular mycorrhizal colonization on the intraradical growth of Phytophthora nicotianae in tomato. MYCORRHIZA 2009; 19:443-448. [PMID: 19488792 DOI: 10.1007/s00572-009-0257-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Accepted: 05/14/2009] [Indexed: 05/27/2023]
Abstract
We studied the role of modification in root exudation induced by colonization with Glomus intraradices and Glomus mosseae in the growth of Phytophthora nicotianae in tomato roots. Plants were grown in a compartmentalized plant growth system and were either inoculated with the AM fungi or received exudates from mycorrhizal plants, with the corresponding controls. Three weeks after planting, the plants were inoculated or not with P. nicotianae growing from an adjacent compartment. At harvest, P. nicotianae biomass was significantly reduced in roots colonized with G. intraradices or G. mosseae in comparison to non-colonized roots. Conversely, pathogen biomass was similar in non-colonized roots supplied with exudates collected from mycorrhizal or non-mycorrhizal roots, or with water. We cannot rule out that a mycorrhiza-mediated modification in root exudation may take place, but our results did not support that a change in pathogen chemotactic responses to host root exudates may be involved in the inhibition of P. nicotianae.
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Affiliation(s)
- L Lioussanne
- Institut de recherche en biologie végétale, Université de Montréal & Jardin botanique de Montréal, 4101 East Sherbrooke Street, Montreal, QC, H1X 2B2, Canada
| | - M Jolicoeur
- Bio-P2 Research Unit, Department of Chemical Engineering, École Polytechnique de Montréal, P.O. Box 6079, Centre-ville Station, Montreal, QC, H3C 3A7, Canada
| | - M St-Arnaud
- Institut de recherche en biologie végétale, Université de Montréal & Jardin botanique de Montréal, 4101 East Sherbrooke Street, Montreal, QC, H1X 2B2, Canada.
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18
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Kong P, Moorman GW, Lea-Cox JD, Ross DS, Richardson PA, Hong C. Zoosporic tolerance to pH stress and its implications for Phytophthora species in aquatic ecosystems. Appl Environ Microbiol 2009; 75:4307-14. [PMID: 19429548 PMCID: PMC2704844 DOI: 10.1128/aem.00119-09] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2009] [Accepted: 05/04/2009] [Indexed: 11/20/2022] Open
Abstract
Phytophthora species, a group of destructive plant pathogens, are commonly referred to as water molds, but little is known about their aquatic ecology. Here we show the effect of pH on zoospore survival of seven Phytophthora species commonly isolated from irrigation reservoirs and natural waterways and dissect zoospore survival strategy. Zoospores were incubated in a basal salt liquid medium at pH 3 to 11 for up to 7 days and then plated on a selective medium to determine their survival. The optimal pHs differed among Phytophthora species, with the optimal pH for P. citricola at pH 9, the optimal pH for P. tropicalis at pH 5, and the optimal pH for the five other species, P. citrophthora, P. insolita, P. irrigata, P. megasperma, and P. nicotianae, at pH 7. The greatest number of colonies was recovered from zoospores of all species plated immediately after being exposed to different levels of pH. At pH 5 to 11, the recovery rate decreased sharply (P < or = 0.0472) after 1-day exposure for five of the seven species. In contrast, no change occurred (P > or = 0.1125) in the recovery of any species even after a 7-day exposure at pH 3. Overall, P. megasperma and P. citricola survived longer at higher rates in a wider range of pHs than other species did. These results are generally applicable to field conditions as indicated by additional examination of P. citrophthora and P. megasperma in irrigation water at different levels of pH. These results challenge the notion that all Phytophthora species inhabit aquatic environments as water molds and have significant implications in the management of plant diseases resulting from waterborne microbial contamination.
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Affiliation(s)
- Ping Kong
- Virginia Polytechnic Institute and State University, Hampton Roads Agricultural Research and Extension Center, Virginia Beach, 23455, USA
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19
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Gene expression changes during asexual sporulation by the late blight agent Phytophthora infestans occur in discrete temporal stages. Mol Genet Genomics 2008; 281:193-206. [DOI: 10.1007/s00438-008-0407-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Accepted: 11/15/2008] [Indexed: 10/21/2022]
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Ranathunge K, Thomas RH, Fang X, Peterson CA, Gijzen M, Bernards MA. Soybean root suberin and partial resistance to root rot caused by Phytophthora sojae. PHYTOPATHOLOGY 2008; 98:1179-89. [PMID: 18943406 DOI: 10.1094/phyto-98-11-1179] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Phytophthora sojae is the causal agent of root and stem rot of soybean (Glycine max). Various cultivars with partial resistance to the pathogen have been developed to mitigate this damage. Herein, two contrasting genotypes, the cultivar Conrad (with strong partial resistance) and the line OX760-6 (with weak partial resistance), were compared regarding their amounts of preformed and induced suberin components, and to early events during the P. sojae infection process. To colonize the root, hyphae grew through the suberized middle lamellae between epidermal cells. This took 2 to 3 h longer in Conrad than in OX760-6, giving Conrad plants more time to establish their chemical defenses. Subsequent growth of hyphae through the endodermis was also delayed in Conrad. This cultivar had more preformed aliphatic suberin than the line OX760-6 and was induced to form more aliphatic suberin several days prior to that of OX760-6. However, the induced suberin was formed subsequent to the initial infection process. Eventually, the amount of induced suberin (measured 8 days postinoculation) was the same in both genotypes. Preformed root epidermal suberin provides a target for selection and development of new soybean cultivars with higher levels of expression of partial resistance to P. sojae.
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22
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Walker CA, Köppe M, Grenville-Briggs LJ, Avrova AO, Horner NR, McKinnon AD, Whisson SC, Birch PRJ, van West P. A putative DEAD-box RNA-helicase is required for normal zoospore development in the late blight pathogen Phytophthora infestans. Fungal Genet Biol 2008; 45:954-62. [PMID: 18439859 DOI: 10.1016/j.fgb.2008.03.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2007] [Revised: 03/10/2008] [Accepted: 03/12/2008] [Indexed: 01/24/2023]
Abstract
The asexual multinucleated sporangia of Phytophthora infestans can germinate directly through a germ tube or indirectly by releasing zoospores. The molecular mechanisms controlling sporangial cytokinesis or sporangial cleavage, and zoospore release are largely unknown. Sporangial cleavage is initiated by a cold shock that eventually compartmentalizes single nuclei within each zoospore. Comparison of EST representation in different cDNA libraries revealed a putative ATP-dependent DEAD-box RNA-helicase gene in P. infestans, Pi-RNH1, which has a 140-fold increased expression level in young zoospores compared to uncleaved sporangia. RNA interference was employed to determine the role of Pi-RNH1 in zoospore development. Silencing efficiencies of up to 99% were achieved in some transiently-silenced lines. These Pi-RNH1-silenced lines produced large aberrant zoospores that had undergone partial cleavage and often had multiple flagella on their surface. Transmission electron microscopy revealed that cytoplasmic vesicles fused in the silenced lines, resulting in the formation of large vesicles. The Pi-RNH1-silenced zoospores were also sensitive to osmotic pressure and often ruptured upon release from the sporangia. These findings indicate that Pi-RNH1 has a major function in zoospore development and its potential role in cytokinesis is discussed.
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Affiliation(s)
- Claire A Walker
- Aberdeen Oomycete Group, College of Life Science and Medicine, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
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23
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Attard A, Gourgues M, Galiana E, Panabières F, Ponchet M, Keller H. Strategies of attack and defense in plant-oomycete interactions, accentuated for Phytophthora parasitica Dastur (syn. P. Nicotianae Breda de Haan). JOURNAL OF PLANT PHYSIOLOGY 2008; 165:83-94. [PMID: 17766006 DOI: 10.1016/j.jplph.2007.06.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2007] [Revised: 06/11/2007] [Accepted: 07/12/2007] [Indexed: 05/17/2023]
Abstract
Oomycetes from the genus Phytophthora are fungus-like plant pathogens that are devastating for agriculture and natural ecosystems. Due to their particular physiological characteristics, no efficient treatments against diseases caused by these microorganisms are presently available. To develop such treatments, it appears essential to dissect the molecular mechanisms that determine the interaction between Phytophthora species and host plants. Available data are scarce, and genomic approaches were mainly developed for the two species, Phytophthora infestans and Phytophthora sojae. However, these two species are exceptions from, rather than representative species for, the genus. P. infestans is a foliar pathogen, and P. sojae infects a narrow range of host plants, while the majority of Phytophthora species are quite unselective, root-infecting pathogens. To represent this majority, Phytophthora parasitica emerges as a model for the genus, and genomic resources for analyzing its interaction with plants are developing. The aim of this review is to assemble current knowledge on cytological and molecular processes that are underlying plant-pathogen interactions involving Phytophthora species and in particular P. parasitica, and to place them into the context of a hypothetical scheme of co-evolution between the pathogen and the host.
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Affiliation(s)
- Agnès Attard
- Unité Mixte de Recherches, Interactions Plantes-Microorganismes et Santé Végétale, INRA1064-CNRS6192-UNSA, BP 167, 400 Route des Chappes, 06903 Sophia Antipolis, France
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24
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Raftoyannis Y, Dick MW. Zoospore encystment and pathogenicity of Phytophthora and Pythium species on plant roots. Microbiol Res 2006; 161:1-8. [PMID: 16338584 DOI: 10.1016/j.micres.2005.04.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/10/2005] [Indexed: 10/25/2022]
Abstract
Seven plant species (lucerne, maize, oat, sugarbeet, sorghum, tomato, wheat) and 12 Pythium and Phytophthora species were used in a comparative study designed to investigate the effects of plant and oomycete inter-specific variation on zoospore encystment density and pathogenicity. Zoospores showed differential encystment behaviour and they encysted more on dicotyledonous than on monocotyledonous plants. Pythium aphanidermatum, P. deliense, and Phytophthora nicotianae were the most aggressive species. Sugarbeet was the most severely attacked plant species followed by tomato while oat plants were relatively unaffected. The relationship between zoospore encystment on roots and disease severity depended on the oomycete-plant combination. Correlation analysis between zoospore encystment density and disease severity indicated low and no significant levels (p.05) of association for most plant-oomycete combinations.
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25
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Jönsson U. A conceptual model for the development of Phytophthora disease in Quercus robur. THE NEW PHYTOLOGIST 2006; 171:55-67. [PMID: 16771982 DOI: 10.1111/j.1469-8137.2006.01743.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Here, a conceptual model is presented for the development of Phytophthora disease in pedunculate oak. The model is presented using the causal loop diagram tool and gives an overview of how various abiotic and biotic factors, such as soil moisture, nutrient availability and mycorrhizal colonization, may affect the reproduction and the infective capacity of soil-borne Phytophthora species, the susceptibility of the host and subsequent disease development. It is suggested that the link between the root damage caused by Phytophthora species and overall tree vitality is in the assimilation and allocation of carbon within the plants. The potential impact of environmental factors on these processes is discussed. The model is presented with reference to scenarios related to variation in soil moisture and nutrient availability. The need for species-specific validation of the model and the implications of the model are discussed.
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Affiliation(s)
- U Jönsson
- Plant Ecology and Systematics, Department of Ecology, Ecology Building, Lund University, Lund, Sweden.
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26
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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.
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Affiliation(s)
- Flavio A Blanco
- Center for Plant Cell Biology and Department of Plant Pathology, University of California, Riverside, CA 92521, USA
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27
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Abstract
Members of the genus Phytophthora are among the most serious threats to agriculture and food production, causing devastating diseases in hundreds of plant hosts. These fungus-like eukaryotes, which are taxonomically classified as oomycetes, generate asexual and sexual spores with characteristics that greatly contribute to their pathogenic success. The spores include survival and dispersal structures, and potent infectious propagules capable of actively locating hosts. Genetic tools and genomic resources developed over the past decade are now allowing detailed analysis of these important stages in the Phytophthora life cycle.
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Affiliation(s)
- Howard S Judelson
- Department of Plant Pathology and Center for Plant Cell Biology, University of California, Riverside, California 92521, USA.
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28
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Appiah AA, van West P, Osborne MC, Gow NAR. Potassium homeostasis influences the locomotion and encystment of zoospores of plant pathogenic oomycetes. Fungal Genet Biol 2005; 42:213-23. [PMID: 15707842 DOI: 10.1016/j.fgb.2004.11.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2004] [Revised: 11/12/2004] [Accepted: 11/13/2004] [Indexed: 11/30/2022]
Abstract
Zoospores of plant pathogenic oomycetes exhibit distinct swimming speeds and patterns under natural conditions. Zoospore swimming is influenced by ion homeostasis and changes in the ionic composition of media. Therefore, we used video microscopy to investigate swimming patterns of five oomycete species in response to changes in potassium homeostasis. In general, zoospore speed tended to be negatively correlated with zoospore size. Three Phytophthora species (Phytophthora palmivora, Phytophthora megakarya, and Phytophthora infestans) swam in straight patterns with speeds ranging from 50 to 250 microm/s whereas two Pythium species (Pythium aphanidermatum and Pythium dissotocum) swam at similar speeds ranging from 180 to 225 microm/s with a pronounced helical trajectory and varying amplitudes. High external concentrations of potassium salts reduced the swimming speed of Ph. palmivora and induced encystment. This was not observed for Py. aphanidermatum. Application of the potassium ionophores gramicidin, nigericin and valinomycin resulted in reduced swimming speeds and changes in the swimming patterns of the Phytophthora species. Therefore, potassium ions play a key role in regulating zoospore behavior.
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Affiliation(s)
- Alex A Appiah
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, Scotland, UK
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29
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Abstract
Mycology is changing as an era of extensive genome sequencing comes of age and provides vital information that enables questions to be addressed about fungi in all the major taxonomic groups. As technology transfer facilitates what was once only possible for a very small number of model species, it becomes possible to explore the biology and biodiversity of fungi as a whole. The availability of genome sequence information and reverse genetic technologies allows hypotheses that emerge from biological observations to be tested. Genomic and post-genomic technologies will underline the importance of fungi as excellent models for the study of fundamental biological phenomena. Two enduring areas of research in my own laboratory are described that are now being extended using post-genomic approaches. These projects relate to how fungal hyphae extend and guide their tips and secondly how plant pathogenic oomycete zoospores are guided on their journey to the plant surface.
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Affiliation(s)
- Neil A R Gow
- School of Medical Sciences, Institute of Medical Science, University of Aberdeen, Aberdeen AB25 2ZD, UK.
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Packer A, Clay K. Development of negative feedback during successive growth cycles of black cherry. Proc Biol Sci 2004; 271:317-24. [PMID: 15058444 PMCID: PMC1691590 DOI: 10.1098/rspb.2003.2583] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Negative feedback between plant and soil microbial communities can be a key determinant of vegetation structure and dynamics. Previous research has shown that negative feedback between black cherry (Prunus serotina) and soil pathogens is strongly distance dependent. Here, we investigate the temporal dynamics of negative feedback. To examine short-term changes, we planted successive cycles of seedlings in the same soil. We found that seedling mortality increased steadily with growth cycle when sterile background soil was inoculated with living field soil but not in controls inoculated with sterilized field soil. To examine long-term changes, we quantified negative feedback across successive growth cycles in soil inoculated with living field soil from a mature forest system (more than 70 years old) versus a younger successional site (ca. 25 years old). In both cases negative feedback developed similarly. Our results suggest that negative feedback can develop very quickly in forest systems, at the spatial scale of a single seedling.
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Affiliation(s)
- Alissa Packer
- Department of Biology, Indiana University, Bloomington 47405, USA.
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Latijnhouwers M, Ligterink W, Vleeshouwers VGAA, van West P, Govers F. A Galpha subunit controls zoospore motility and virulence in the potato late blight pathogen Phytophthora infestans. Mol Microbiol 2004; 51:925-36. [PMID: 14763970 DOI: 10.1046/j.1365-2958.2003.03893.x] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The heterotrimeric G-protein pathway is a ubiquitous eukaryotic signalling module that is known to regulate growth and differentiation in many plant pathogens. We previously identified Pigpa1, a gene encoding a G-protein alpha subunit from the potato late blight pathogen Phytophthora infestans. P. infestans belongs to the class oomycetes, a group of organisms in which signal transduction processes have not yet been studied at the molecular level. To elucidate the function of Pigpa1, PiGPA1-deficient mutants were obtained by homology-dependent gene silencing. The Pigpa1-silenced mutants produced zoospores that turned six to eight times more frequently, causing them to swim only short distances compared with wild type. Attraction to the surface, a phenomenon known as negative geotaxis, was impaired in the mutant zoospores, as well as autoaggregation and chemotaxis towards glutamic and aspartic acid. Zoospore production was reduced by 20-45% in different Pigpa1-silenced mutants. Transformants expressing constitutively active forms of PiGPA1, containing amino acid substitutions (R177H and Q203L), showed no obvious phenotypic differences from the wild-type strain. Infection efficiencies on potato leaves ranged from 3% to 14% in the Pigpa1-silenced mutants, compared with 77% in wild type, showing that virulence is severely impaired. The results prove that PiGPA1 is crucial for zoospore motility and for pathogenicity in an important oomycete plant pathogen.
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Affiliation(s)
- Maita Latijnhouwers
- Laboratory of Phytopathology, Wageningen University, Binnenhaven, The Netherlands
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32
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Skalamera D, Wasson AP, Hardham AR. Genes expressed in zoospores of Phytophthora nicotianae. Mol Genet Genomics 2003; 270:549-57. [PMID: 14652735 DOI: 10.1007/s00438-003-0946-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2003] [Accepted: 10/17/2003] [Indexed: 11/27/2022]
Abstract
The genus Phytophthora includes many highly destructive plant pathogens. In many Phytophthora species, pathogen dispersal and initiation of plant infection are achieved by motile, biflagellate zoospores that are chemotactically attracted to suitable infection sites. In order to study gene expression in zoospores, we have constructed a cDNA library using mRNA from zoospores of Phytophthora nicotianae. The library was arrayed and screened using probes derived from mycelium or zoospore mRNA. More than 400 clones representing genes preferentially expressed in zoospores were identified and sequenced from the 5' end of the insert. The expressed sequence tags (ESTs) generated were found to represent 240 genes. The ESTs were compared to sequences in GenBank and in the Phytophthora Genome Consortium database, and classified according to putative function based on homology to known proteins. To further characterize the identified genes, a colony array was created on replicate nylon filters and screened with probes derived from four Phytophthora developmental stages including zoospores, germinating cysts, vegetative mycelium and sporulating hyphae, and from inoculated and uninoculated tobacco seedlings. Data from sequence analysis and colony array screening were compiled into a local database, and searched to identify genes that are preferentially expressed in zoospores for future functional analysis.
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Affiliation(s)
- D Skalamera
- Cooperative Research Centre for Tropical Plant Protection and Plant Cell Biology Group, Research School of Biological Sciences, Australian National University, ACT 2601, Canberra, Australia.
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De Souza JT, De Boer M, De Waard P, Van Beek TA, Raaijmakers JM. Biochemical, genetic, and zoosporicidal properties of cyclic lipopeptide surfactants produced by Pseudomonas fluorescens. Appl Environ Microbiol 2003; 69:7161-72. [PMID: 14660362 PMCID: PMC309978 DOI: 10.1128/aem.69.12.7161-7172.2003] [Citation(s) in RCA: 182] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2003] [Accepted: 09/04/2003] [Indexed: 11/20/2022] Open
Abstract
Zoospores play an important role in the infection of plant and animal hosts by oomycetes and other zoosporic fungi. In this study, six fluorescent Pseudomonas isolates with zoosporicidal activities were obtained from the wheat rhizosphere. Zoospores of multiple oomycetes, including Pythium species, Albugo candida, and Phytophthora infestans, were rendered immotile within 30 s of exposure to cell suspensions or cell culture supernatants of the six isolates, and subsequent lysis occurred within 60 s. The representative strain SS101, identified as Pseudomonas fluorescens biovar II, reduced the surface tension of water from 73 to 30 mN m-1. The application of cell suspensions of strain SS101 to soil or hyacinth bulbs provided significant protection against root rot caused by Pythium intermedium. Five Tn5 mutants of strain SS101lacked the abilities to reduce the surface tension of water and to cause lysis of zoospores. Genetic characterization of two surfactant-deficient mutants showed that the transposons had integrated into condensation domains of peptide synthetases. A partially purified extract from strain SS101 reduced the surface tension of water to 30 mN m-1 and reached the critical micelle concentration at 25 micrograms ml-1. Reverse-phase high-performance liquid chromatography yielded eight different fractions, five of which had surface activity and caused lysis of zoospores. Mass spectrometry and nuclear magnetic resonance analyses allowed the identification of the main constituent as a cyclic lipopeptide (1,139 Da) containing nine amino acids and a 10-carbon hydroxy fatty acid. The other four zoosporicidal fractions were closely related to the main constituent, with molecular massesranging from 1,111 to 1,169 Da.
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Affiliation(s)
- Jorge T De Souza
- Laboratory of Phytopathology, Department of Plant Sciences, Wageningen University, 6709 PD Wageningen, The Netherlands
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34
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Reinhart KO, Packer A, Van der Putten WH, Clay K. Plant-soil biota interactions and spatial distribution of black cherry in its native and invasive ranges. Ecol Lett 2003. [DOI: 10.1046/j.1461-0248.2003.00539.x] [Citation(s) in RCA: 271] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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35
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de Souza JT, Arnould C, Deulvot C, Lemanceau P, Gianinazzi-Pearson V, Raaijmakers JM. Effect of 2,4-diacetylphloroglucinol on pythium: cellular responses and variation in sensitivity among propagules and species. PHYTOPATHOLOGY 2003; 93:966-75. [PMID: 18943863 DOI: 10.1094/phyto.2003.93.8.966] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
ABSTRACT The antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) plays an important role in the suppression of plant pathogens by several strains of Pseudomonas spp. Based on the results of this study, there is variation within and among Pythium spp. to 2,4-DAPG. Also, various propagules of Pythium ultimum var. sporangiiferum, that are part of the asexual stage of the life cycle, differ considerably in their sensitivity to 2,4-DAPG. Mycelium was the most resistant structure, followed by zoosporangia, zoospore cysts, and zoospores. Additionally, we report for the first time that pH has a significant effect on the activity of 2,4-DAPG, with a higher activity at low pH. Furthermore, the level of acetylation of phloroglucinols is also a major determinant of their activity. Transmission electron microscopy studies revealed that 2,4-DAPG causes different stages of disorganization in hyphal tips of Pythium ultimum var. sporangiiferum, including alteration (proliferation, retraction, and disruption) of the plasma membrane, vacuolization, and cell content disintegration. The implications of these results for the efficacy and consistency of biological control of plant-pathogenic Pythium spp. by 2,4-DAPG-producing Pseudomonas spp. are discussed.
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Abstract
Pythiosis, lagenidiosis, and zygomycosis affect animals living in temperate, tropical, and subtropical climates, and these diseases are often fatal. Although Pythium insidiosum, Conidiobolus species, and Basidiobolus species have been recognized as pathogens for several years, members of the genus Lagenidium have been identified as a cause of oomycosis in dogs only recently. Pythiosis, lagenidiosis, and zygomycosis share similar clinical and histologic characteristics, making them difficult to distinguish from one another; however, distinguishing between these pathogens is important because of differences in epidemiology, choice and duration of therapy, and prognosis.
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Affiliation(s)
- Amy M Grooters
- Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
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Shepherd SJ, van West P, Gow NAR. Proteomic analysis of asexual development of Phytophthora palmivora. MYCOLOGICAL RESEARCH 2003; 107:395-400. [PMID: 12825510 DOI: 10.1017/s0953756203007561] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Two-dimensional gel electrophoresis was used to analyse stage-specific proteins from Phytophthora palmivora, a pathogen of cocoa and other economically important tropical crops. Approximately 1% of proteins appeared to be specific for each of the mycelial, sporangial, zoospore, cyst and germinated cyst stages of the life-cycle. Three proteins excised from protein gels of P. palmivora were identified as isoforms of actin by database searches to public libraries of Phytophthora infestans. The protein profiles of parallel samples of P. palmivora and P. infestans demonstrated that 30% of proteins precisely co-migrated suggesting that proteomics may be used to examine changes in the specific stages in the life cycles of Phytophthora spp.
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Affiliation(s)
- Samantha J Shepherd
- Department of Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
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38
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Judelson HS, Roberts S. Novel protein kinase induced during sporangial cleavage in the oomycete Phytophthora infestans. EUKARYOTIC CELL 2002; 1:687-95. [PMID: 12455688 PMCID: PMC126747 DOI: 10.1128/ec.1.5.687-695.2002] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2002] [Accepted: 07/09/2002] [Indexed: 11/20/2022]
Abstract
A study of the effect of inhibitors on zoospore development in Phytophthora infestans demonstrated the involvement of protein kinases and calcium and led to the discovery of a gene induced during zoosporogenesis that encoded a protein resembling Ca2+- and calmodulin-regulated serine/threonine protein kinases. The calcium channel blocker verapamil and the calmodulin antagonist trifluoroperazine inhibited zoosporogenesis and encystment. The protein kinase inhibitors K-252a and KN-93 inhibited zoospore release, encystment, and cyst germination, and K-252a reduced zoospore viability. In contrast, the inhibitors had minor or no effects on sporangia directly germinating in media. Spurred by these findings, a survey of putative protein kinase genes was performed to identify any that were up-regulated during zoosporogenesis. A kinase-encoding gene was identified for which mRNA accumulation was first detected soon after chilling sporangia in water, conditions that induce sporangial cytoplasm to cleave and release zoospores. The transcript persisted in motile zoospores and in germinated cysts but was not detected in other tissues, including hyphae, hyphae placed in water, or directly germinating sporangia. The structure of the predicted protein was novel, as its C-terminal region, which binds calmodulin in related proteins, was unusually short. Concentrations of actinomycin D previously used in experiments that suggested that de novo transcription was not needed for zoosporogenesis or encystment only partially inhibited transcription of the kinase gene, probably due to poor uptake into sporangia.
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Affiliation(s)
- Howard S Judelson
- Department of Plant Pathology, University of California, Riverside, California 92521, USA.
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van West P, Morris BM, Reid B, Appiah AA, Osborne MC, Campbell TA, Shepherd SJ. Oomycete plant pathogens use electric fields to target roots. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2002; 15:790-798. [PMID: 12182336 DOI: 10.1094/mpmi.2002.15.8.790] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Plant roots generate electrical currents and associated electrical fields as a consequence of electrogenic ion transport at the root surface. Here we demonstrate that the attraction of swimming zoospores of oomycete plant pathogens to plant roots is mediated in part by electrotaxis in natural root-generated electric fields. The zones of accumulation of anode- or cathode-seeking zoospores adjacent to intact and wounded root surfaces correlated with their in vitro electrotactic behavior. Manipulation of the root electrical field was reflected in changes in the pattern of zoospore accumulation and imposed focal electrical fields were capable of overriding endogenous signals at the root surface. The overall pattern of zoospore accumulation around roots was not affected by the presence of amino acids at concentrations expected within the rhizosphere, although higher concentrations induced encystment and reduced root targeting. The data suggest that electrical signals can augment or override chemical ones in mediating short-range tactic responses of oomycete zoospores at root surfaces.
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Affiliation(s)
- P van West
- Department of Biomedical Sciences, Institute of Medical Sciences, University of Aberdeen, Scotland, UK
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40
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Bishop-Hurley SL, Mounter SA, Laskey J, Morris RO, Elder J, Roop P, Rouse C, Schmidt FJ, English JT. Phage-displayed peptides as developmental agonists for Phytophthora capsici zoospores. Appl Environ Microbiol 2002; 68:3315-20. [PMID: 12089009 PMCID: PMC126814 DOI: 10.1128/aem.68.7.3315-3320.2002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
As part of its pathogenic life cycle, Phytophthora capsici disperses to plants through a motile zoospore stage. Molecules on the zoospore surface are involved in reception of environmental signals that direct preinfection behavior. We developed a phage display protocol to identify peptides that bind to the surface molecules of P. capsici zoospores in vitro. The selected phage-displayed peptides contained an abundance of polar amino acids and proline but were otherwise not conserved. About half of the selected phage that were tested concomitantly induced zoospore encystment in the absence of other signaling agents. A display phage was shown to bind to the zoospore but not to the cyst form of P. capsici. Two free peptides corresponding to active phage were similarly able to induce encystment of zoospores, indicating that their ability to serve as signaling ligands did not depend on their exact molecular context. Isolation and subsequent expression of peptides that act on pathogens could allow the identification of receptor molecules on the zoospore surface, in addition to forming the basis for a novel plant disease resistance strategy.
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Affiliation(s)
- Sharon L Bishop-Hurley
- Department of Plant Microbiology and Patholog, University of Missouri, Columbia, MO 65211, USA
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41
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París R, Lamattina L. Increased ratio of mitochondrial rDNA to cytoplasmic rDNA during zoosporic and germinating cyst stages of the life cycle of Phytophthora infestans (Mont.) de Bary. Can J Microbiol 2002; 48:268-74. [PMID: 11989772 DOI: 10.1139/w01-141] [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: 11/22/2022]
Abstract
A differential RNA display approach was used to study the gene expression in zoospores (Z) and germinating cysts (GC) of the late blight pathogen Phytophthora infestans. Four differentially amplified cDNAs were selected and cloned. The clone pGPiZ0.5 showed a 2.7-kb transcript highly expressed in Z. A BLAST search revealed an almost full sequence homology (98%) to the P. infestans mitochondrial large subunit rRNA. Northern blot analysis showed a twofold accumulation of the mitochondrial rRNA (mit rRNA) in Z compared with that of GC and mycelia of P. infestans. The high level of mit rRNA in Z might reflect an increased number of gene copies, an increased rDNA transcription rate, or both. Dot blot experiments indicated that the amount of mitochondrial rDNA (mit rDNA) relative to cytoplasmic rDNA is twofold higher in Z and GC than in mycelia. This relatively elevated mit rDNA could explain the high level of mit rRNA in the zoosporic phase. On the contrary, GC conserves the mit rDNA content, but the level of mit rRNA drops to 50% that of Z. The data are consistent with a very active mitochondrial protein synthesis during zoosporic phase, followed by a rapid down-regulation of mitochondrial activity during cyst formation.
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Affiliation(s)
- Ramiro París
- Instituto de Investigaciones Biólogicas, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Argentina
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42
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Tyler BM. Molecular basis of recognition between phytophthora pathogens and their hosts. ANNUAL REVIEW OF PHYTOPATHOLOGY 2002; 40:137-167. [PMID: 12147757 DOI: 10.1146/annurev.phyto.40.120601.125310] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Recognition is the earliest step in any direct plant-microbe interaction. Recognition between Phytophthora pathogens, which are oomycetes, phylogenetically distinct from fungi, has been studied at two levels. Recognition of the host by the pathogen has focused on recognition of chemical, electrical, and physical features of plant roots by zoospores. Both host-specific factors such as isoflavones, and host-nonspecific factors such as amino acids, calcium, and electrical fields, influence zoospore taxis, encystment, cyst germination, and hyphal chemotropism in guiding the pathogen to potential infection sites. Recognition of the pathogen by the host defense machinery has been analyzed using biochemical and genetic approaches. Biochemical approaches have identified chemical elicitors of host defense responses, and in some cases, their cognate receptors from the host. Some elicitors, such as glucans and fatty acids, have broad host ranges, whereas others such as elicitins have narrow host ranges. Most elicitors identified appear to contribute primarily to basic or nonhost resistance. Genetic analysis has identified host resistance (R) genes and pathogen avirulence (Avr) genes that interact in a gene-for-gene manner. One Phytophthora Avr gene, Avr1b from P. sojae, has been cloned and characterized. It encodes a secreted elicitor that triggers a system-wide defense response in soybean plants carrying the cognate R gene, Rps1b.
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Affiliation(s)
- Brett M Tyler
- Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, Blacksburg 24061, USA.
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43
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Heungens K, Parke JL. Zoospore homing and infection events: effects of the biocontrol bacterium Burkholderia cepacia AMMDR1 on two oomycete pathogens of pea (Pisum sativum L.). Appl Environ Microbiol 2000; 66:5192-200. [PMID: 11097889 PMCID: PMC92443 DOI: 10.1128/aem.66.12.5192-5200.2000] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2000] [Accepted: 09/18/2000] [Indexed: 11/20/2022] Open
Abstract
Burkholderia cepacia AMMDR1 is a biocontrol agent that protects pea and sweet corn seeds from Pythium damping-off in field experiments. The goal of this work was to understand the effect of B. cepacia AMMDR1 on Pythium aphanidermatum and Aphanomyces euteiches zoospore homing events and on infection of pea seeds or roots. In vitro, B. cepacia AMMDR1 caused zoospore lysis, prevented cyst germination, and inhibited germ tube growth of both oomycetes. B. cepacia AMMDR1 also reduced the attractiveness of seed exudates to Pythium zoospores to nondetectable levels. However, when present at high levels on seeds, B. cepacia AMMDR1 had little net effect on zoospore attraction, probably because it also enhanced seed exudation. Seed-applied B. cepacia AMMDR1 dramatically reduced the incidence of infection by Pythium zoospores in situ compared with an antibiosis-deficient Tn5 mutant strain. This mutant strain also decreased Pythium infection incidence to some extent, but only when the pathogen inoculum potential was low. B. cepacia AMMDR1 did not affect attraction of Aphanomyces zoospores or Aphanomyces root rot incidence. These results suggest that B. cepacia AMMDR1 controls P. aphanidermatum largely through antibiosis, but competition for zoospore-attracting compounds can contribute to the effect. Differences in suppression of Aphanomyces and Pythium are discussed in relation to differences in the ecology of the two pathogens.
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Affiliation(s)
- K Heungens
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Martin RR, James D, Lévesque CA. Impacts of Molecular Diagnostic Technologies on Plant Disease Management. ANNUAL REVIEW OF PHYTOPATHOLOGY 2000; 38:207-239. [PMID: 11701842 DOI: 10.1146/annurev.phyto.38.1.207] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Detection and diagnosis of plant viruses has included serological laboratory tests since the 1960s. Relatively little work was done on serological detection of plant pathogenic bacteria and fungi prior to the development of ELISA and monoclonal antibody technologies. Most applications for laboratory-based tests were directed at virus detection with relatively little emphasis on fungal and bacterial pathogens, though there was some good work done with other groups of plant pathogens. With the advent of molecular biology and the ability to compare regions of genomic DNA representing conserved sequences, the development of laboratory tests increased at an amazing rate for all groups of plant pathogens. Comparison of ITS regions of bacteria, fungi, and nematodes has proven useful for taxonomic purposes. Sequencing of conserved genes has been used to develop PCR-based detection with varying levels of specificity for viruses, fungi, and bacteria. Combinations of ELISA and PCR technologies are used to improve sensitivity of detection and to avoid problems with inhibitors or PCR often found in plants. The application of these technologies in plant pathology has greatly improved our ability to detect plant pathogens and is increasing our understanding of, their ecology and epidemiology.
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Affiliation(s)
- Robert R Martin
- USDA-ARS Horticulture Crops Research Laboratory, 3420 NW Orchard Avenue, Corvallis, Oregon 97330; e-mail:
| | - Delano James
- Centre for Plant Health, Canadian Food Inspection Agency, 8801 East Saanich Road, Sidney, British Columbia V8l 1H3, Canada; e-mail:
| | - C André Lévesque
- Eastern Cereal and Oilseed Research Center (ECORC), Agriculture and Agri-Food Canada, 960 Carling Avenue, Ottawa, Ontario K1A OC6, Canada; e-mail:
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van West P, Reid B, Campbell TA, Sandrock RW, Fry WE, Kamoun S, Gow NA. Green fluorescent protein (GFP) as a reporter gene for the plant pathogenic oomycete Phytophthora palmivora. FEMS Microbiol Lett 1999; 178:71-80. [PMID: 10483725 DOI: 10.1111/j.1574-6968.1999.tb13761.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Transgenic Phytophthora palmivora strains that produce green fluorescent protein (GFP) or beta-glucuronidase (GUS) constitutively were obtained after stable DNA integration using a polyethylene-glycol and CaCl2-based transformation protocol. GFP and GUS production were monitored during several stages of the life cycle of P. palmivora to evaluate their use in molecular and physiological studies. 40% of the GFP transformants produced the GFP to a level detectable by a confocal laser scanning microscope, whereas 75% of the GUS transformants produced GUS. GFP could be visualised readily in swimming zoospores and other developmental stages of P. palmivora cells. For high magnification microscopic studies, GFP is better visualised and was superior to GUS. In contrast, for macroscopic examination, GUS was superior. Our findings indicate that both GFP and GUS can be used successfully as reporter genes in P. palmivora.
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Affiliation(s)
- P van West
- Department of Molecular and Cell Biology, University of Aberdeen, Foresterhill, UK.
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46
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Warburton AJ, Deacon JW. Transmembrane Ca2+ fluxes associated with zoospore encystment and cyst germination by the phytopathogen phytophthora parasitica. Fungal Genet Biol 1998; 25:54-62. [PMID: 9806806 DOI: 10.1006/fgbi.1998.1086] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Phytophthora spp. can infect plants within 30 min of a zoospore arriving at a host surface. The infection sequence from zoospore encystment to cyst germination and host penetration seems to be largely preprogrammed and dependent on calcium signaling. Here we present evidence that the encystment process leading to autonomous germination in Phytophthora parasitica may be coordinated by sequential net Ca2+ fluxes across the cell membrane, which we assessed by fluorimetry of the probe fura-2 in zoospore bathing medium. Encystment was associated with a large initial net Ca2+ influx, which was abolished by the channel blockers La3+ and verapamil. The net influx was followed by a larger, progressive net Ca2+ efflux over 20-30 min, which was associated with cyst germination but was inhibited by TMB-8, implicating Ca2+ release from intracellular stores. The effects of inhibitors were overcome by high (1 mM) exogenous Ca2+, enabling encystment and germination. Copyright 1998 Academic Press.
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Affiliation(s)
- AJ Warburton
- Institute of Cell and Molecular Biology, University of Edinburgh, Daniel Rutherford Building, King's Buildings, Edinburgh, EH9 3JH, United Kingdom
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47
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Germination triggers of zoospore cysts of Aphanomyces euteiches and Phytophthora parasitica. ACTA ACUST UNITED AC 1998. [DOI: 10.1017/s0953756297004358] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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48
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von Broembsen SL, Deacon JW. Calcium Interference with Zoospore Biology and Infectivity of Phytophthora parasitica in Nutrient Irrigation Solutions. PHYTOPATHOLOGY 1997; 87:522-528. [PMID: 18945107 DOI: 10.1094/phyto.1997.87.5.522] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
ABSTRACT Calcium, applied as either CaCl2 or Ca(NO3)2 to water or calcium-free soluble fertilizer solution (Peters 20-10-20 Peat Lite Special), affected several important stages of Phytophthora parasitica zoospore behavior relevant to infection and disease spread. Release of zoospores from sporangia was suppressed by Ca(2+) concentrations in the range of 10 to 50 meq. These concentrations also curtailed zoospore motility; 20 meq of Ca(2+) in fertilizer solution caused all zoospores to encyst within 4 h, whereas 94% of zoospores remained motile in unamended solution. In addition, Ca(2+) in the range of 10 to 30 meq stimulated zoospore cysts to germinate in the absence of an organic nutrient trigger, while suppressing the release of a single zoospore (diplanetism) from cysts that did not germinate. In growth chamber experiments, the amendment of the fertilizer solution with 10 or 20 mM Ca(NO3)2 greatly suppressed infection of flood-irrigated, containerized vinca seedlings in a peat-based mix by motile or encysted zoospores of P. parasitica. These results demonstrate that Ca(2+) amendments interfere with P. parasitica zoospore biology at multiple stages, with compounding effects on epidemiology, and suggest that manipulation of Ca(2+) levels in irrigation water or fertilizer solutions could contribute to management of Phytophthora in recirculating irrigation systems.
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49
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Orientated zoospore attachment and cyst germination in Catenaria anguillulae, a facultative endoparasite of nematodes. ACTA ACUST UNITED AC 1997. [DOI: 10.1017/s0953756296003085] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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50
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Effects of calcium on germination and further zoospore release from zoospore cysts of Phytophthora parasitica. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s0953-7562(96)80085-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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