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1
Maier, Michelle A., Kimiko Uchii, Tawnya D. Peterson, and Maiko Kagami. "Evaluation of Daphnid Grazing on Microscopic Zoosporic Fungi by Using Comparative Threshold Cycle Quantitative PCR." Applied and Environmental Microbiology 82, no. 13 (April 22, 2016): 3868–74. http://dx.doi.org/10.1128/aem.00087-16.
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ABSTRACTLethal parasitism of large phytoplankton by chytrids (microscopic zoosporic fungi) may play an important role in organic matter and nutrient cycling in aquatic environments by shunting carbon away from hosts and into much smaller zoospores, which are more readily consumed by zooplankton. This pathway provides a mechanism to more efficiently retain carbon within food webs and reduce export losses. However, challenges in accurate identification and quantification of chytrids have prevented a robust assessment of the relative importance of parasitism for carbon and energy flows within aquatic systems. The use of molecular techniques has greatly advanced our ability to detect small, nondescript microorganisms in aquatic environments in recent years, including chytrids. We used quantitative PCR (qPCR) to quantify the consumption of zoospores byDaphniain laboratory experiments using a culture-based comparative threshold cycle (CT) method. We successfully quantified the reduction of zoospores in water samples duringDaphniagrazing and confirmed the presence of chytrid DNA inside the daphnid gut. We demonstrate that comparativeCTqPCR is a robust and effective method to quantify zoospores and evaluate zoospore grazing by zooplankton and will aid in better understanding how chytrids contribute to organic matter cycling and trophic energy transfer within food webs.IMPORTANCEThe study of aquatic fungi is often complicated by the fact that they possess complex life cycles that include a variety of morphological forms. Studies that rely on morphological characteristics to quantify the abundances of all stages of the fungal life cycle face the challenge of correctly identifying and enumerating the nondescript zoospores. These zoospores, however, provide an important trophic link between large colonial phytoplankton and zooplankton: that is, once the carbon is liberated from phytoplankton into the parasitic zoospores, the latter are consumed by zooplankton and carbon is retained in the aquatic food web rather than exported from the system. This study provides a tool to quantify zoospores and evaluate the consumption of zoospores by zooplankton in order to further our understanding of their role in food web dynamics.
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Shipton, WA. "Regulation by Ions of Zoospore Release in Pythium." Australian Journal of Botany 35, no. 1 (1987): 79. http://dx.doi.org/10.1071/bt9870079.
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In a Pythium species causing equine phycomycosis, release of zoospores from vesicles is regulated by K+ in the presence of either Ca2+ or Mg2+ . In the presence of K+ (16 mM ) , numerous vesicles were formed but, in most, mature zoospores failed to develop to maturity and both immature zoospores and vesicles disintegrated unless Ca,2+ (0.3�M -3mM ) or Mg2+ (0.3�M - 0.3mM) were present. The effect of K+ can be replaced partially by Rb+. Addition of Li+, Cs+ or NH4+ ions to colonies 4 h after zoospore induction had commenced led to vesicle lysis and to the formation of abnormal spores and bizarre-shaped bodies in vesicles; simultaneous addition of Ca2+ (3mM) exerted a particularly marked stabilising effect on vesicle structure. Zoospore motility both in the vesicle and after release was reduced or completely inhibited by K+ (16 mM) . Group I elements generally inhibited zoospore motility with the notable exception of Na+. Some group 11 elements inhibited zoospore motility but Ca2+ and Mg2+ were notable exceptions. Vesicle membranes induced in the presence of K+ and Ca2+ (16 and 3 mM respectively) were up to eight times thicker than membranes induced in distilled water. Zoospore motility, zoospore encystment and membrane stability appear to be critical factors in the release of zoospores from vesicles.
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Kong, Ping, and Chuanxue Hong. "Zoospore Density-Dependent Behaviors of Phytophthora nicotianae Are Autoregulated by Extracellular Products." Phytopathology® 100, no. 7 (July 2010): 632–37. http://dx.doi.org/10.1094/phyto-100-7-0632.
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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 Ca2+ in ZFF. These results suggest that Ca2+ 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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von Broembsen, Sharon L., and J. W. Deacon. "Calcium Interference with Zoospore Biology and Infectivity of Phytophthora parasitica in Nutrient Irrigation Solutions." Phytopathology® 87, no. 5 (May 1997): 522–28. http://dx.doi.org/10.1094/phyto.1997.87.5.522.
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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 Ca2+ concentrations in the range of 10 to 50 meq. These concentrations also curtailed zoospore motility; 20 meq of Ca2+ in fertilizer solution caused all zoospores to encyst within 4 h, whereas 94% of zoospores remained motile in unamended solution. In addition, Ca2+ 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 Ca2+ amendments interfere with P. parasitica zoospore biology at multiple stages, with compounding effects on epidemiology, and suggest that manipulation of Ca2+ levels in irrigation water or fertilizer solutions could contribute to management of Phytophthora in recirculating irrigation systems.
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Liu, Fang, Bao-hua Li, Sen Lian, Xiang-li Dong, Cai-xia Wang, Zhen-fang Zhang, and Wen-xing Liang. "Effects of Temperature and Moisture on the Infection and Development of Apple Fruit Rot Caused by Phytophthora cactorum." Plant Disease 102, no. 9 (September 2018): 1811–19. http://dx.doi.org/10.1094/pdis-07-17-1028-re.
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Phytophthora fruit rot, caused by Phytophthora cactorum, is an important disease of apple in China, often causing more than 50% fruit rot in rainy years. We examined the effects of temperature and moisture on the development of the disease and effects of the variables on zoospore release and germination, infection, and lesion development. In vitro, a temperature range of 5 to 20°C had no significant effects on zoospore release dynamics but did significantly affect the quantities of released zoospores. The largest quantity of zoospores was released at 9.9°C according to a fitted model. Zoosporangia released zoospores within 15 min at the test temperatures (0 to 20°C), which peaked at the fourth hour. Zoospores germinated in vitro, requiring free water, at temperatures from 5 to 35°C. The optimum germination temperature was 25.1°C according to a fitted model. The minimum wetness duration required for zoospores to complete the infection process and induce visible lesions on Fuji fruit was 0.40 h at the optimal temperature of 23.0°C according to the fitted model, whereas observed values were 4.5, 1.5, 0.5, 1.5 and 8.5 h at 10, 15, 20, 25, and 30°C, respectively. The number of zoospore infections on fruit at various temperatures and wetness durations were well fitted by the modified Weibull model; based on the model, the optimal temperature for zoospore infections was 23.0°C. Young apple fruit infected by zoospores developed visible lesions from 10 to 30°C, with a predicted optimum of 23.5°C; no lesions developed at 5 or 35°C. The shortest incubation period of the disease was 4 days. These results can be used to develop disease forecasting models for improved fungicide control.
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Kakani, Kishore, Marjorie Robbins, and D'Ann Rochon. "Evidence that Binding of Cucumber Necrosis Virus to Vector Zoospores Involves Recognition of Oligosaccharides." Journal of Virology 77, no. 7 (April 1, 2003): 3922–28. http://dx.doi.org/10.1128/jvi.77.7.3922-3928.2003.
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ABSTRACT Despite the importance of vectors in natural dissemination of plant viruses, relatively little is known about the molecular features of viruses and vectors that permit their interaction in nature. Cucumber necrosis virus (CNV) is a small spherical virus whose transmission in nature is facilitated by zoospores of the fungus Olpidium bornovanus. Previous studies have shown that specific regions of the CNV capsid are involved in transmission and that transmission defects in several CNV transmission mutants are due to inefficient attachment of virions to the zoospore surface. In this study, we have undertaken to determine if zoospores contain specific receptors for CNV. We show that in vitro binding of CNV to zoospores is saturable and that vector zoospores bind CNV more efficiently than nonvector zoospores. Further studies show that treatment of zoospores with periodate and trypsin reduces CNV binding, suggesting the involvement of glycoproteins in zoospore attachment. In virus overlay assays, CNV binds to several proteins, whereas CNV transmission mutants either fail to bind or bind at significantly reduced levels. The possible involvement of specific sugars in attachment was investigated by incubating CNV with zoospores in the presence of various sugars. Two mannose derivatives (methyl α-d-mannopyranoside and d-mannosamine), as well as three mannose-containing oligosaccharides (mannotriose, α3,α6-mannopentaose, and yeast mannan) and l-(−)-fucose, all inhibited CNV binding at relatively low concentrations. Taken together, our studies suggest that binding of CNV to zoospores is mediated by specific mannose and/or fucose-containing oligosaccharides. This is the first time sugars have been implicated in transmission of a plant virus.
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Erb, W. A., J. N. Moore, and R. E. Sterne. "Attraction of Phytophthora cinnamomi Zoospores to Blueberry Roots." HortScience 21, no. 6 (December 1986): 1361–63. http://dx.doi.org/10.21273/hortsci.21.6.1361.
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Abstract The attraction of zoospores of Phytophthora cinnamomi Rands to roots of three cultivars of rabbiteye blueberry (Vaccinium ashei Reade), two species hybrid cultivars of highbush blueberry, and one tetraploid species hybrid selection (US 109) was compared. Zoospores were attracted to the roots of all plants tested. Roots of highbush cultivars ‘Bluetta’ and ‘Patriot’ attracted more zoospores than the rabbiteye cultivars. The number of zoospores attracted to roots of US 109 was greater than the number attracted to the three rabbiteye cultivars, but less than the highbush cultivars. Increased zoospore attraction appeared to be related to root rot susceptibility in blueberries.
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Kasteel, Michiel, Tharun P. Rajamuthu, Joris Sprakel, Tijs Ketelaar, and Francine Govers. "Phytophthora zoospores display klinokinetic behaviour in response to a chemoattractant." PLOS Pathogens 20, no. 9 (September 30, 2024): e1012577. http://dx.doi.org/10.1371/journal.ppat.1012577.
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Microswimmers are single-celled bodies powered by flagella. Typical examples are zoospores, dispersal agents of oomycete plant pathogens that are used to track down hosts and infect. Being motile, zoospores presumably identify infection sites using chemical cues such as sugars, alcohols and amino acids. With high-speed cameras we traced swimming trajectories of Phytophthora zoospores over time and quantified key trajectory parameters to investigate chemotactic responses. Zoospores adapt their native run-and-tumble swimming patterns in response to the amino acid glutamic acid by increasing the rate at which they turn. Simulations predict that tuneable tumble frequencies are sufficient to explain zoospore aggregation, implying positive klinokinesis. Zoospores thus exploit a retention strategy to remain at the plant surface once arriving there. Interference of G-protein mediated signalling affects swimming behaviour. Zoospores of a Phytophthora infestans G⍺-deficient mutant show higher tumbling frequencies but still respond and adapt to glutamic acid, suggesting chemoreception to be intact.
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Pozdnyakov, Igor R., Alexei O. Seliuk, Kristina O. Barzasekova, and Sergey A. Karpov. "Gene Expression in Aphelid Zoospores Reveals Their Transcriptional and Translational Activity and Alacrity for Invasion." Journal of Fungi 11, no. 1 (January 16, 2025): 68. https://doi.org/10.3390/jof11010068.
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In Aphelidium insulamus (Opisthokonta, Aphelida) zoospores, the expression of 7708 genes out of 7802 described genes was detected. For 589 of them, expression levels were shown to be more than 10 times higher than the median level. Among the highly expressed genes with known functions, the largest functional categories were “Cellular Metabolism”, “Protein Synthesis”, “Cell State Control”, and “Nucleic Acid Processing”. Unlike fungal zoospores, translational and transcriptional activity was demonstrated for A. insulamus zoospores. With increasing temperature, the expression of many zoospore genes changed dramatically; the expression of heat shock and chaperone protein genes multiplied more than 30 times, indicating the high sensitivity of aphelid zoospores and their response to environmental changes.
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Kerwin, James L., Lisa M. Johnson, Howard C. Whisler, and Amy R. Tuininga. "Infection and morphogenesis of Pythium marinum in species of Porphyra and other red algae." Canadian Journal of Botany 70, no. 5 (May 1, 1992): 1017–24. http://dx.doi.org/10.1139/b92-126.
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A strain of Pythium marinum (Peronosporales: Pythiaceae) from Puget Sound, Washington, was isolated from lesions of Porphyra nereocystis. The fungus grew on a modified Vishniac medium, from temperatures of 4 to 25 °C, although growth was slow at the lowest temperature. Sexual and asexual reproduction also occurred within this temperature range. Mycelium diluted in seawater initiated zoospore release within 16 h and continued to release zoospores for over 200 h at temperatures from 4 to 20 °C. Zoospore encystment on several species of marine red, brown, and green algae was readily monitored following staining with lactophenol – cotton blue. Pythium marinum zoospore encystment occurred on rhodophyceaen species, including Porphyra (gametophytes), Gigartina exasperata (tetrasporophyte), Mastocarpus papillatus (gametophyte), Prionitis lanceolata (nonfertile), and Iridaea heterocarpa (gametophyte and tetrasporophyte), but not on Nereocystis leutkeana or Ulva lactuca. Over 50% of zoospores held in half-strength seawater at 4 and 20 °C encysted within 24 h, whereas those held at 12 °C reached 50% encystment only after 32 h. For 4-mm diameter discs of Porphyra nereocystis and Porphyra perforata (formerly Porphyra sanjuanensis) blades, there was only a transient relationship between cell damage and number of encysted zoospores. Zoospores did not attach to the conchocelis phase of two species of Porphyra. Sequential extraction of carbohydrates from the blades of Porphyra perforata implicated separate chemical signals for zoospore encystment and appressorium formation prior to the initiation of blade invasion. Addition of diverse monosaccharides and polysaccharides to zoospore suspensions suggested that these chemical signals are specific, with the attachment–encystment signal chemically related to polysaccharides consisting of sulfated or nonsulfated galactose and 3,6-anhydrogalactose found in commercial agars and carrageenans. There was no consistent relationship between zoospore encystment and the amount of 3,6-anhydrogalactose present in the blade phase of several species of red algae. Key words: Pythium, Porphyra, zoospore, encystment, sulfated galactans, 3,6-anhydrogalactose.
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Bacic, A., M. L. Williams, and A. E. Clarke. "Studies on the cell surface of zoospores and cysts of the fungus Phytophthora cinnamomi: nature of the surface saccharides as determined by quantitative lectin binding studies." Journal of Histochemistry & Cytochemistry 33, no. 5 (May 1985): 384–88. http://dx.doi.org/10.1177/33.5.3838761.
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The nature of the surface saccharides of zoospores, "partially encysted zoospores" and cysts of the root-rotting fungus Phytophthora cinnamomi, has been examined by quantitative lectin binding studies. Zoospores bound concanavalin A (Con A), but did not bind any of a variety of other lectins tested. In contrast, both cysts and "partially encysted zoospores" bound soybean agglutinin (SBA) as well as Con A. This indicates that accessible alpha-D-glucosyl/alpha-D-mannosyl-containing glycoconjugates predominate at the zoospore surface, whereas both alpha-D-glucosyl/alpha-D-mannosyl and galactosyl and/or N-acetyl-D-galactosaminosyl residues are accessible at the surface of cysts and "partially encysted zoospores." Neither Ulex europeus lectin nor wheat germ agglutinin (WGA) bound to any of the three cell preparations, indicating the absence of accessible alpha-L-fucosyl and N-acetyl-D-glucosaminosyl residues.
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Goldberg, N. P., M. C. HAwes, and M. E. Stanghellini. "Specific attraction to and infection of cotton root cap cells by zoospores of Pythium dissotocum." Canadian Journal of Botany 67, no. 6 (June 1, 1989): 1760–67. http://dx.doi.org/10.1139/b89-223.
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Root cap cells of two cotton species (Gossypium barbadense L. and G. hirsutum L.) elicited a specific chemotactic response in zoospores of Pythium dissotocum. When roots of cotton seedlings were placed into a suspension of Pythium dissotocum zoospores, there was immediate attraction, accumulation, and encystment exclusively in the root cap region. Seedlings which attracted zoospores were killed within 24 h. Furthermore, root cap cells remained attractive when isolated nondestructively from the root and placed into a zoospore suspension; attraction, accumulation, and encystment on individual root cap cells occurred within seconds after contact. Penetration and death of isolated cells occurred within 15–30 min. After 30 min, approximately 25% of living cells were directly colonized by zoospores. Root cap cells killed by freezing or drying remained attractive but at a reduced level; approximately half as many killed cells as living cells were directly colonized by zoospores. The number of root cap cells directly colonized by zoospores did not increase with time. In contrast, zoospores of Pythium catenulatum that exhibited a chemotactic response to Agrostis palustris (Bentgrass) were not attracted to and did not infect cotton seedlings or isolated root cap cells.
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Granke, L. L., and M. K. Hausbeck. "Effects of Temperature, Concentration, Age, and Algaecides on Phytophthora capsici Zoospore Infectivity." Plant Disease 94, no. 1 (January 2010): 54–60. http://dx.doi.org/10.1094/pdis-94-1-0054.
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Controlled laboratory studies were undertaken to determine the effects of water temperature (2, 9, 12, 19, 22, and 32°C), inoculum concentration (1 × 102, 1 × 103, 5 × 103, 1 × 104, 2 × 104, and 4 × 104 zoospores/ml), and zoospore suspension age (0, 1, 3, and 5 days old) on infection of pickling cucumbers (Cucumis sativus) by Phytophthora capsici. Zoospore motility and mortality in response to commercial algaecides were also investigated. Cucumbers became infected at all temperatures tested, except 2°C, and the highest infection incidence was observed for cucumbers incubated in suspensions held at ≥19°C. Fewer fruit (<40% at ≥19°C, 0% at ≤12°C) became infected when water contained 1 × 102 zoospores/ml. Almost 100% of fruit were infected when water contained ≥5 × 103 zoospores/ml at temperatures ≥12°C. While the incidence of fruit infection declined with the zoospore suspension age, infection still occurred when 5-day-old suspensions were used. Commercial algaecides inhibited zoospore motility and caused significant zoospore mortality in laboratory assays, and show promise for treatment of infested irrigation water. Avoidance of infested irrigation water throughout the growing season is warranted until effective and economically acceptable water treatments are developed for field use.
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Wang, Yonglin, Aining Li, Xiaoli Wang, Xin Zhang, Wei Zhao, Daolong Dou, Xiaobo Zheng, and Yuanchao Wang. "GPR11, a Putative Seven-Transmembrane G Protein-Coupled Receptor, Controls Zoospore Development and Virulence of Phytophthora sojae." Eukaryotic Cell 9, no. 2 (December 11, 2009): 242–50. http://dx.doi.org/10.1128/ec.00265-09.
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ABSTRACT G protein-coupled receptors (GPCRs) represent a large receptor family involved in a broad spectrum of cell signaling. To understand signaling mechanisms mediated by GPCRs in Phytophthora sojae, we identified and characterized the PsGPR11 gene, which encodes a putative seven-transmembrane GPCR. An expression analysis revealed that PsGPR11 was differentially expressed during asexual development. The highest expression level occurred in zoospores and was upregulated during early infection. PsGPR11-deficienct transformants were obtained by gene silencing strategies. Silenced transformants exhibited no differences in hyphal growth or morphology, sporangium production or size, or mating behavior. However, the release of zoospores from sporangia was severely impaired in the silenced transformants, and about 50% of the sporangia did not completely release their zoospores. Zoospore encystment and germination were also impaired, and zoospores of the transformants lost their pathogenicity to soybean. In addition, no interaction was observed between PsGPR11 and PsGPA1 with a conventional yeast two-hybrid assay, and the transcriptional levels of some genes which were identified as being negatively regulated by PsGPA1 were not clearly altered in PsGPR11-silenced mutants. These results suggest that PsGPR11-mediated signaling controls P. sojae zoospore development and virulence through the pathways independent of G protein.
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Widmer, T. L. "Infective Potential of Sporangia and Zoospores of Phytophthora ramorum." Plant Disease 93, no. 1 (January 2009): 30–35. http://dx.doi.org/10.1094/pdis-93-1-0030.
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Phytophthora species produce sporangia that either germinate directly or release zoospores, depending upon environmental conditions. Previous Phytophthora spp. inoculation trials have used both sporangia and zoospores as the inoculum type. However, it is unknown what impact propagule type has on disease. Rhododendron leaf disks were inoculated with P. ramorum zoospores (75, 500, or 2,400 per disk), sporangia (75 per disk), or sporangia plus trifluoperazine hydrochloride (TFP) (75 per disk), a chemical that inhibits zoospore formation. Combining results from two different isolates, the highest concentration of zoospores (2,400 per disk) induced a significantly higher percentage of necrotic leaf disk area (96.6%) than sporangia (87.6%) and 500 zoospores per disk (88.7%). The sporangia plus TFP treatment had the lowest necrosis at 47.5%. Rooted rhododendron cuttings had a higher percentage of necrotic leaves per plant when inoculated with zoospores (3,000 or 50,000 per ml) or cysts (50,000 per ml) than with sporangia (3,000 per ml) with or without TFP. The percentage of necrotic leaf area was significantly higher when cysts or zoospores were inoculated at 50,000 per ml than sporangia without TFP and zoospores at 3,000 per ml. All treatments were significantly higher in the percentage of necrotic leaf area than the leaves treated with sporangia plus TFP. This demonstrates that the full inoculum potential may not be achieved when sporangia are used as the inoculum propagule.
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van West, P., B. M. Morris, B. Reid, A. A. Appiah, M. C. Osborne, T. A. Campbell, S. J. Shepherd, and N. A. R. Gow. "Oomycete Plant Pathogens Use Electric Fields to Target Roots." Molecular Plant-Microbe Interactions® 15, no. 8 (August 2002): 790–98. http://dx.doi.org/10.1094/mpmi.2002.15.8.790.
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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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Powell, Martha J., and Sonali Roychoudhury. "Ultrastructural organization of Rhizophlyctis harderi zoospores and redefinition of the type 1 microbody – lipid globule complex." Canadian Journal of Botany 70, no. 4 (April 1, 1992): 750–61. http://dx.doi.org/10.1139/b92-096.
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Because ultrastructural features of zoospores are considered primary characters in Chytridiomycete systematics, computer-aided three-dimensional reconstructions of serial sections were used to analyze zoospore fine structure of Rhizophlyctis harderi, a questionable member of the genus Rhizophlyctis. A secondary centriole was parallel to the kinetosome, but the nucleus was not structurally or spatially associated with the kinetosomes. Mitochondria and cisternae associated with vesicles bounded a ribosomal aggregation in which the nucleus was partially embedded. The peripheral cytoplasm between the plasma membrane and ribosomal aggregation contained α-glycogen particles, vacuoles with osmiophilic globules, vesicles with clear matrices, and vesicles with electron-dense cores. A new, compound form of microbody – lipid globule complex (MLC) was identified. This type of MLC incorporated posteriorly located lipid globules associated with rumposomes and anteriorly located lipid globules associated with simple cisternae, microbodies, and highly branched mitochondria. Based on these and other recent observations, the concept of the type 1 MLC was redefined. Sources for variation in ultrastructural features of zoospores are discussed. Zoospore ultrastructure of R. harderi is different from that described for other chytrid zoospores. Key words: Chytridiomycetes, microbody – lipid globule complex, Rhizophlyctis, taxonomy, ultrastructure, zoospore.
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Bassani, Ilaria, Corinne Rancurel, Sophie Pagnotta, François Orange, Nicolas Pons, Kevin Lebrigand, Franck Panabières, Laurent Counillon, Xavier Noblin, and Eric Galiana. "Transcriptomic and Ultrastructural Signatures of K+-Induced Aggregation in Phytophthora parasitica Zoospores." Microorganisms 8, no. 7 (July 7, 2020): 1012. http://dx.doi.org/10.3390/microorganisms8071012.
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Most pathogenic oomycetes of the genus Phytophthora spread in water films as flagellated zoospores. Zoospores perceive and produce signals attracting other zoospores, resulting in autoaggregation in vitro or biofilm formation on plant surface. The mechanisms underlying intercellular communication and consequent attraction, adhesion and aggregation are largely unknown. In Phytophthora parasitica, the perception of a K+ gradient induces coordinated motion and aggregation. To define cellular and molecular events associated with oomycete aggregation, we combined transcriptomic and ultrastructural analyses. Results indicate involvement of electroception in K+ sensing. They establish that the transcriptome repertoire required for swimming and aggregation is already fully functional at zoospore release. At the time points analyzed, aggregates are mainly constituted of zoospores. They produce vesicular and fibrillary material discharged at cell-to-cell contacts. Consistently, the signature of transcriptome dynamics during transition to aggregates is an upregulation of genes potentially related to vesicular trafficking. Moreover, transcriptomic and functional analyses show a strong enhancement of carbonic anhydrase activity, indicating that pH homeostasis may contribute to aggregation by acting on both zoospore movement and adhesion. This study poses the molecular and cellular bases of aggregative behavior within oomycetes and expands the current knowledge of ion perception-mediated dissemination of propagules in the rhizosphere.
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Galiana, Eric, Celine Cohen, Philippe Thomen, Catherine Etienne, and Xavier Noblin. "Guidance of zoospores by potassium gradient sensing mediates aggregation." Journal of The Royal Society Interface 16, no. 157 (August 2019): 20190367. http://dx.doi.org/10.1098/rsif.2019.0367.
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The biflagellate zoospores of some phytopathogenic Phytophthora species spontaneously aggregate within minutes in suspension. We show here that Phytophthora parasitica zoospores can form aggregates in response to a K + gradient with a particular geometric arrangement. Using time-lapse live imaging in macro- and microfluidic devices, we defined (i) spatio-temporal and concentration-scale changes in the gradient, correlated with (ii) the cell distribution and (iii) the metrics of zoospore motion (velocity, trajectory). In droplets, we found that K + -induced aggregates resulted from a single biphasic temporal sequence involving negative chemotaxis followed by bioconvection over a K + gradient concentration scale [0–17 mM]. Each K + -sensing cell moved into a region in which potassium concentration is below the threshold range of 1–4 mM, resulting in swarming. Once a critical population density had been achieved, the zoospores formed a plume that migrated downward, with fluid advection in its wake and aggregate formation on the support surface. In the microfluidic device, the density of zoospores escaping potassium was similar to that achieved in droplets. We discuss possible sources of K + gradients in the natural environment (zoospore population, microbiota, plant roots, soil particles), and implications for the events preceding inoculum formation on host plants.
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Rebollar-Alviter, A., L. V. Madden, S. N. Jeffers, and M. A. Ellis. "Baseline and Differential Sensitivity to Two QoI Fungicides Among Isolates of Phytophthora cactorum That Cause Leather Rot and Crown Rot on Strawberry." Plant Disease 91, no. 12 (December 2007): 1625–37. http://dx.doi.org/10.1094/pdis-91-12-1625.
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Sensitivities of 89 isolates of Phytophthora cactorum, the causal agent of crown rot and leather rot on strawberry plants, from seven states (Florida, Maine, North Carolina, Ohio, Oregon, South Carolina, and New York) to the QoI fungicide azoxystrobin were determined based on mycelium growth and zoospore germination. Radial growth of mycelia on lima bean agar amended with azoxystrobin at 0.001, 0.01, 0.1, 1.0, 10, and 30 μg/ml and salicylhydroxamic acid (SHAM) at 100 μg/ml was measured after 6 days. Effect on zoospore germination was evaluated in aqueous solutions of azoxystrobin at 0.005, 0.01, 0.05, 0.1, 0.5, and 1.0 μg/ml in 96-well microtiter plates by counting germinated and nongerminated zoospores after 4 h at room temperature. SHAM was not used to evaluate zoospore sensitivity. The effective dose to reduce mycelium growth by 50% (ED50) ranged from 0.16 to 12.52 μg/ml for leather rot isolates and 0.10 to 15 μg/ml for crown rot isolates. The Kolmogorov-Smirnov test showed significant differences (P < 0.001) between the two distributions. Zoospores were much more sensitive to azoxystrobin than were mycelia. Differences between sensitivity distributions for zoospores from leather rot and crown rot isolates were significant at P = 0.05. Estimated ED50 values ranged from 0.01 to 0.24 μg/ml with a median of 0.04 μg/ml. Experiments with pyraclostrobin, another QoI fungicide, demonstrated that both mycelia and zoospores of P. cactorum were more sensitive to pyraclostrobin than to azoxystrobin. Sensitivities to azoxystrobin and pyraclostrobin were moderately but significantly correlated (r = 0.60, P = 0.0001).
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Widmer, T. L. "Cryopreservation of Synchytrium solstitiale In Planta." Plant Disease 90, no. 4 (April 2006): 429–32. http://dx.doi.org/10.1094/pd-90-0429.
Full textAbstract:
The fungus Synchytrium solstitiale is a candidate for use as a biocontrol agent against Centaurea solstitialis. This obligate parasite can be propagated only in planta, which necessitates development of a method for preserving cultures for longer periods of time for routine biological studies and shipment to other laboratories. Normally, sporangia embedded within the plant tissue release zoospores when submersed in water at temperatures above freezing. To examine what chemicals might inhibit zoospore release, infected tissue was exposed to different suspensions of fungicides. Cycloheximide and benomyl completely inhibited zoospore release or immediately induced encystment from tissue stored in these two chemicals, respectively. A few zoospores were released in suspensions of iprodione and propionic acid but were not motile. However, when tissue stored in iprodione or propionic acid was transferred to fresh distilled water, abundant active zoospores were released. Freezing the infected tissue at different temperatures in different cryoprotectants also affected the release of motile zoospores. Infected C. solstitialis tissue was immersed in water, water plus iprodione, methanol, ethylene glycol, dimethyl sulfoxide, glycerol, skim milk, trehalose, or sucrose and subjected to different temperatures for various periods of time. Some treatments protected the viability of the fungus for a shorter period of time whereas other treatments completely inhibited release. The best results were obtained when infected tissue was stored at -2°C in 0.5 M sucrose where active zoospores were released after 12 weeks of storage. Overall, results obtained from this study demonstrate a technique for long-term storage of S. solstitiale.
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Hua, Chenlei, Yonglin Wang, Xiaobo Zheng, Daolong Dou, Zhengguang Zhang, Francine Govers, and Yuanchao Wang. "A Phytophthora sojae G-Protein α Subunit Is Involved in Chemotaxis to Soybean Isoflavones." Eukaryotic Cell 7, no. 12 (October 17, 2008): 2133–40. http://dx.doi.org/10.1128/ec.00286-08.
Full textAbstract:
ABSTRACT For the soybean pathogen Phytophthora sojae, chemotaxis of zoospores to isoflavones is believed to be critical for recognition of the host and for initiating infection. However, the molecular mechanisms underlying this chemotaxis are largely unknown. To investigate the role of G-protein and calcium signaling in chemotaxis, we analyzed the expression of several genes known to be involved in these pathways and selected one that was specifically expressed in sporangia and zoospores but not in mycelium. This gene, named PsGPA1, is a single-copy gene in P. sojae and encodes a G-protein α subunit that shares 96% identity in amino acid sequence with that of Phytophthora infestans. To elucidate the function, expression of PsGPA1 was silenced by introducing antisense constructs into P. sojae. PsGPA1 silencing did not disturb hyphal growth or sporulation but severely affected zoospore behavior, including chemotaxis to the soybean isoflavone daidzein. Zoospore encystment and cyst germination were also altered, resulting in the inability of the PsGPA1-silenced mutants to infect soybean. In addition, the expressions of a calmodulin gene, PsCAM1, and two calcium- and calmodulin-dependent protein kinase genes, PsCMK3 and PsCMK4, were increased in the mutant zoospores, suggesting that PsGPA1 negatively regulates the calcium signaling pathways that are likely involved in zoospore chemotaxis.
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Kong, Ping. "Carbon Dioxide as a Potential Water Disinfestant for Phytophthora Disease Risk Mitigation." Plant Disease 97, no. 3 (March 2013): 369–72. http://dx.doi.org/10.1094/pdis-09-12-0844-re.
Full textAbstract:
The spread of Phytophthora spp. through irrigation systems and natural waterways can have a significant impact on plant health and requires mitigation. Pressurized carbon dioxide (CO2) can inactivate Phytophthora nicotianae zoospores but its effectiveness at low pressure and on other species was unknown. This study evaluated the effect of injected CO2 at 63 to 4,000 ppm in irrigation water on zoospore survival of four Phytophthora spp. and infectivity of P. nicotianae zoospores. Zoospore survival of P. nicotianae, P. tropicalis, and P. pini was reduced by over 90% at 4,000 ppm and was reduced by 40% at 125 to 2,000 ppm after a 2-h exposure. Survival of P. megasperma was less affected by injected CO2, with a reduction of 37.1% at ≤4,000 ppm. CO2 treatments at 4,000 ppm for 30 or 120 min of water infested with P. nicotianae at zoospore concentrations of 1,000 and 5,000 ml−1 reduced disease incidence of annual vinca (Catharanthus roseus) by 92 and 75%. Comparable efficacy was observed in the CO2 treatment at 2,000 ppm. The CO2 treatments at <2,000 ppm also significantly reduced disease caused by water infested at 1,000 zoospores ml−1. These results indicate that CO2 may have potential as a safe and effective water disinfestant for Phytophthora spp.
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Downer, A. J., J. A. Menge, and E. Pond. "Effects of Cellulytic Enzymes on Phytophthora cinnamomi." Phytopathology® 91, no. 9 (September 2001): 839–46. http://dx.doi.org/10.1094/phyto.2001.91.9.839.
Full textAbstract:
Two enzyme systems, cellulase (β-1,4-glucanase) and laminarinase (β-1,3-glucanase), were added to soil extracts to simulate (in vitro) lytic components found in mulches suppressive to Phytophthora cinnamomi. Concentration ranges of each enzyme were incubated with Phytophthora cinnamomi mycelium, zoospores, zoospores cysts, and zoospore-infected excised roots to evaluate the roles of each enzyme in potential control of avocado root rot disease. Cellulase significantly retarded the development of zoosporangia and chlamydospores when mycelia were incubated in soil extract containing the enzyme at concentrations greater than 10 units/ml. Zoospore production was also reduced by cellulase but not by laminarinase. Laminarinase had little effect on zoosporangia or chlamydospore formation. At high concentrations, laminarinase was consistently more effective at preventing encystment than cellulase. Chlamydospores preformed in root tips were immune to the lytic effects of all treatments except cellulase at 100 units/ml. Zoospores placed in enzyme solutions and plated on a selective medium survived high cellulase concentrations and formed colonies, but there were fewer surviving zoospores when laminarinase was present at greater than 10 units/ml. Low concentrations of cellulase stimulated infection of excised roots, however, low concentrations of laminarinase prevented infection. Cellulase and laminarinase have different effects on the structures of the Phytophthora cinnamomi life history, however, each enzyme may have a role in reduction of inoculum.
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Joint, Ian, Karen Tait, and Glen Wheeler. "Cross-kingdom signalling: exploitation of bacterial quorum sensing molecules by the green seaweed Ulva." Philosophical Transactions of the Royal Society B: Biological Sciences 362, no. 1483 (March 13, 2007): 1223–33. http://dx.doi.org/10.1098/rstb.2007.2047.
Full textAbstract:
The green seaweed Ulva has been shown to detect signal molecules produced by bacteria. Biofilms that release N -acylhomoserine lactones (AHLs) attract zoospores—the motile reproductive stages of Ulva . The evidence for AHL involvement is based on several independent lines of evidence, including the observation that zoospores are attracted to wild-type bacteria that produce AHLs but are not attracted to mutants that do not produce signal molecules. Synthetic AHL also attracts zoospores and the attraction is lost in the presence of autoinducer inactivation (AiiA) protein. The mechanism of attraction is not chemotactic but involves chemokinesis. When zoospores detect AHLs, the swimming rate is reduced and this results in accumulation of cells at the source of the AHL. It has been demonstrated that the detection of AHLs results in calcium influx into the zoospore. This is the first example of a calcium signalling event in a eukaryote in response to bacterial quorum sensing molecules. The role of AHLs in the ecology of Ulva is discussed. It is probable that AHLs act as cues for the settlement of zoospores, rather than being directly involved as a signalling mechanism.
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Imchen, Temjensangba. "Marine Macroalgae: Prospective Hitchhikers of Ship Ballast." ASEAN Journal on Science and Technology for Development 35, no. 1-2 (September 15, 2018): 43–47. http://dx.doi.org/10.29037/ajstd.472.
Full textAbstract:
Invasive alien species, on successful establishment, can displace native species. The threat of invasive species arises in view of their ability to outcompete and destabilize native biodiversity. Invasive species are found across all taxonomic groups of plants, animals and microorganisms. The green macroalga Ulva flexuosa has a potential to become invasive and this species was investigated for its hitchhiking potential under laboratory conditions. Zoospores of U. flexuosa were maintained at 4°C for nearly 10 months in the dark. Recruitment potential of zoospores after dark stress was tested in a modified Provasoli medium under optimal laboratoryconditions. The success rate of zoospore recruitment was 61%. The paper describes the transfer potential through shipping activities by correlating the Ulva zoospores recruitment potential and survivability.
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Kakani, Kishore, Jean-Yves Sgro, and D'Ann Rochon. "Identification of Specific Cucumber Necrosis Virus Coat Protein Amino Acids Affecting Fungus Transmission and Zoospore Attachment." Journal of Virology 75, no. 12 (June 15, 2001): 5576–83. http://dx.doi.org/10.1128/jvi.75.12.5576-5583.2001.
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ABSTRACT Cucumber necrosis virus (CNV) is naturally transmitted in the soil by zoospores of the fungal vector Olpidium bornovanus. Successful transmission requires that virus particles attach to the surface of zoospores prior to zoospore encystment on host roots. Mechanically passaged CNV was screened for mutants deficient in fungus transmission. We found six such mutants, exhibiting transmission efficiencies ranging from approximately 14 to 76% of that of wild-type (WT) CNV. Results of in vitro virus-zoospore binding assays show that each mutant binds to zoospores less efficiently than WT CNV (21 to 68%), suggesting that defects in transmission for these mutants are at least partially due to inefficient zoospore binding. Analysis of the structure of the CNV coat protein subunit and trimer indicates that affected amino acids in all of the mutants are located in the shell or protruding domain and that five of six of them are potentially exposed on the surface of the virus particle. In addition, several of the mutated sites, along with a previously identified site in a region of subunit-subunit interaction in the coat protein shell domain (M. A. Robbins, R. D. Reade, and D. M. Rochon, Virology 234:138–146, 1997), are located on the particle quasi-threefold axis, suggesting that this region of the capsid may be important in recognition of a putative zoospore receptor. The individual sites may directly affect attachment to a receptor or could indirectly affect attachment via changes in virion conformation.
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Bishop-Hurley, Sharon L., Sarah A. Mounter, James Laskey, Roy O. Morris, Jim Elder, Philip Roop, Chris Rouse, Francis J. Schmidt, and James T. English. "Phage-Displayed Peptides as Developmental Agonists for Phytophthora capsici Zoospores." Applied and Environmental Microbiology 68, no. 7 (July 2002): 3315–20. http://dx.doi.org/10.1128/aem.68.7.3315-3320.2002.
Full textAbstract:
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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Wubah, D. A., M. S. Fuller, and D. E. Akin. "Neocallimastix: a comparative morphological study." Canadian Journal of Botany 69, no. 4 (April 1, 1991): 835–43. http://dx.doi.org/10.1139/b91-109.
Full textAbstract:
The development from zoospore to a mature thallus in Neocallimastix sp. isolated from a Georgia cow was studied at the light microscope level. The zoospore had 9–14 posteriorly directed flagella, and its shape varied from amoeboid in agar to ovoid in broth. Encysted zoospores developed endogenously into extramatrical ovoid or spherical incipient zoosporangia with extensively branched intramatrical rhizoids that often had constrictions. Sessile mature zoosporangia varied in shape, and zoospores were fully formed within zoosporangia before release through an apical pore. In agar, zoospores encysted close to the parent zoosporangium and developed endogenously into second generation zoosporangia or exogenously into elongate thalli. At maturity, an elongate thallus was made up of a sporangium, a sporangial stalk, a cyst, and branched rhizoids. Elongate thalli were sometimes formed in broth. Melanized resting sporangia were formed on branched thalli in old (> 36 h) cultures. Two isolates of Neocallimastix frontalis from a cow and sheep and Neocallimastix patriciarum were grown under the same conditions as our isolate, and the morphology of zoospore, zoosporangium, and melanized sporangium of the four isolates were compared. In broth, the isolates developed in the same manner and formed elongate thalli and melanized sporangia as described for our isolate. There is insufficient justification, based on morphology alone, for separating the four isolates. The importance of basic light microscopy is discussed. Key words: Neocallimastix, development, morphology.
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ESTRADA-GARCIA, M. TERESA, JAMES A. CALLOW, and JONATHAN R. GREEN. "Monoclonal antibodies to the adhesive cell coat secreted by Pythium aphanidermatum zoospores recognise 200x103 Mr glycoproteins stored within large peripheral vesicles." Journal of Cell Science 95, no. 2 (February 1, 1990): 199–206. http://dx.doi.org/10.1242/jcs.95.2.199.
Full textAbstract:
During encystment the motile zoospores of the plant pathogen Pythium aphanidermatum secrete an adhesive cell coat that is involved in their attachment to roots. Previous ultrastructural studies have indicated that the adhesive material is pre-packaged within large peripheral vesicles underlying the zoospore plasma membrane. In the present study, four monoclonal antibodies (MAbs) designated PA3-6, which were raised against zoospores and cysts of P. aphanidermatum, were used to re-examine the formation of the adhesive cell coat and to study its molecular nature. Immunogold labelling of zoospores and cysts shows that all the antibodies recognise material contained within the large peripheral vesicles of zoospores. These structures are morphologically distinct from the microbodies, which also underly the plasma membrane, and the latter are not labelled by the antibodies. During encystment the material recognised by the MAbs is secreted to form a cell coat around the zoospores and cysts and this can be seen to be separated from the cyst plasma membrane by a distinct layer (cyst wall). The MAbs also label material within vesicles that are located towards the centre of the cyst cytoplasm. Western blotting and antigen-modification techniques have shown that all the MAbs bind to carbohydrate epitopes of a set of high molecular weight glycoproteins (> 200xl03Mr). One of the antibodies, PA6, also binds to several lower molecular weight components. Overall, the results show that the adhesive material secreted by P. aphanidermatum zoospores is stored within large peripheral vesicles and is composed of several glycoproteins. The results are discussed in the context of studies on the secretion of adhesive material by zoospores of related oomycete fungi.
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Islam, Md Tofazzal, Andreas von Tiedemann, and Hartmut Laatsch. "Protein Kinase C Is Likely to be Involved in Zoosporogenesis and Maintenance of Flagellar Motility in the Peronosporomycete Zoospores." Molecular Plant-Microbe Interactions® 24, no. 8 (August 2011): 938–47. http://dx.doi.org/10.1094/mpmi-12-10-0280.
Full textAbstract:
The motility of zoospores is critical in the disease cycles of Peronosporomycetes that cause devastating diseases in plants, fishes, vertebrates, and microbes. In the course of screening for secondary metabolites, we found that ethyl acetate extracts of a marine Streptomyces sp. strain B5136 rapidly impaired the motility of zoospores of the grapevine downy mildew pathogen Plasmopara viticola at 0.1 μg/ml. The active principle in the extracts was identified as staurosporine, a known broad-spectrum inhibitor of protein kinases, including protein kinase C (PKC). In the presence of staurosporine (2 nM), zoospores moved very slowly in their axis or spun in tight circles, instead of displaying straight swimming in a helical fashion. Compounds such as K-252a, K-252b, and K-252c structurally related to staurosporine also impaired the motility of zoospores in a similar manner but at varying doses. Among the 22 known kinase inhibitors tested, the PKC inhibitor chelerythrine was the most potent to arrest the motility of zoospores at concentrations starting from 5 nM. Inhibitors that targeted kinase pathways other than PKC pathways did not practically show any activity in impairing zoospore motility. Interestingly, both staurosporine (5 nM) and chelerythrine (10 nM) also inhibited the release of zoospores from the P. viticola sporangia in a dose-dependent manner. In addition, staurosporine completely suppressed downy mildew disease in grapevine leaves at 2 μM, suggesting the potential of small-molecule PKC inhibitors for the control of peronosporomycete phytopathogens. Taken together, these results suggest that PKC is likely to be a key signaling mediator associated with zoosporogenesis and the maintenance of flagellar motility in peronosporomycete zoospores.
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Islam, Tofazzal. "Secondary Metabolites from Nonhost Plants Affect the Motility and Viability of Phytopathogenic Aphanomyces cochlioides Zoospores." Zeitschrift für Naturforschung C 63, no. 3-4 (April 1, 2008): 233–40. http://dx.doi.org/10.1515/znc-2008-3-413.
Full textAbstract:
The motile zoospores of the damping-off pathogen Aphanomyces cochlioides aggregate on host plants (e. g., sugar beet, spinach) guided by the host-specific plant signal cochliophilin A before infection. To assess the potential role of secondary metabolites in nonhost resistance, acetone extracts of 200 nonhost traditional medicinal plants from Chinese and Bangladeshi origins were tested for the motility behaviour of A. cochlioides zoospores using a particle bioassay method. Nearly one third of the tested plant extracts exhibited diverse deleterious activities such as repellent, stimulant, motility halting and lysis against A. cochlioides zoospores. Among these active plants, an extract of the Chinese medicinal plant Dalbergia odorifera displayed potent repellent activity toward zoospores. Chromatographic separation of D. odorifera constituents revealed that the repellent activity was regulated by the cumulative effect of three motility-affecting isoflavonoids, viz. (±)-medicarpin (repellent at 150 μg/ml), (-)-claussequinone (stimulant at 100 μg/ml) and formononetin (stimulant and attractant at 50 μg/ml). A mixture (1:1:1, w/w/w) of these three compounds exhibited only repellent activity toward zoospores at a concentration lower than 50 μg/ml. These results suggest that nonhost plants might possess potential bioactive secondary metabolites to ward off zoosporic phytopathogens
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Kuhajek, Jeanne M., Steven N. Jeffers, Marc Slattery, and David E. Wedge. "A Rapid Microbioassay for Discovery of Novel Fungicides for Phytophthora spp." Phytopathology® 93, no. 1 (January 2003): 46–53. http://dx.doi.org/10.1094/phyto.2003.93.1.46.
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A microbioassay was developed for the discovery of compounds that inhibit Phytophthora spp. This assay uses a 96-well format for high-throughput capability and a standardized method for quantitation of initial zoospore concentrations for maximum reproducibility. Zoospore suspensions were quantifiable between 0.7 and 1.5 × 105 zoospores per ml using percent transmittance (620 nm). Subsequent growth of mycelia was monitored by measuring optical density (620 nm) at 24-h intervals for 96 h. Full- and half-strength preparations of each of three media (V8 broth, Roswell Park Memorial Institute mycological broth [RPMI], and mineral salts medium) and four zoospore concentrations (10, 100, 1,000, and 10,000 zoospores per ml) were evaluated. Both full- and half-strength RPMI were identified as suitable synthetic media for growing P. nicotianae, and 1,000 zoospores per ml was established as the optimum initial concentration. The assay was used to determine effective concentration values for 50% growth reduction (EC50) for seven commercial antifungal compounds (azoxystrobin, fosetyl-aluminum, etridiazole, metalaxyl, pentachloronitrobenzene, pimaricin, and propamocarb). These EC50 values were compared with those obtained by measuring linear growth of mycelia on fungicide-amended medium. The microbioassay proved to be a rapid, reproducible, and efficient method for testing the efficacy of compounds that inhibit spore germination in P. nicotianae and should be effective for other species of Phytophthora as well. The assay requires relatively small amounts of a test compound and is suitable for the evaluation of natural product samples.
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Chibucos, M. Constantine, and Paul F. Morris. "Levels of Polyamines and Kinetic Characterization of Their Uptake in the Soybean Pathogen Phytophthora sojae." Applied and Environmental Microbiology 72, no. 5 (May 2006): 3350–56. http://dx.doi.org/10.1128/aem.72.5.3350-3356.2006.
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ABSTRACT Polyamines are ubiquitous biologically active aliphatic cations that are at least transiently available in the soil from decaying organic matter. Our objectives in this study were to characterize polyamine uptake kinetics in Phytophthora sojae zoospores and to quantify endogenous polyamines in hyphae, zoospores, and soybean roots. Zoospores contained 10 times more free putrescine than spermidine, while hyphae contained only 4 times as much free putrescine as spermidine. Zoospores contained no conjugated putrescine, but conjugated spermidine was present. Hyphae contained both conjugated putrescine and spermidine at levels comparable to the hyphal free putrescine and spermidine levels. In soybean roots, cadaverine was the most abundant polyamine, but only putrescine efflux was detected. The selective efflux of putrescine suggests that the regulation of polyamine availability is part of the overall plant strategy to influence microbial growth in the rhizosphere. In zoospores, uptake experiments with [1,4-14C]putrescine and [1,4-14C]spermidine confirmed the existence of high-affinity polyamine transport for both polyamines. Putrescine uptake was reduced by high levels of exogenous spermidine, but spermidine uptake was not reduced by exogenous putrescine. These observations suggest that P. sojae zoospores express at least two high-affinity polyamine transporters, one that is spermidine specific and a second that is putrescine specific or putrescine preferential. Disruption of polyamine uptake or metabolism has major effects on a wide range of cellular activities in other organisms and has been proposed as a potential control strategy for Phytophthora. Inhibition of polyamine uptake may be a means of reducing the fitness of the zoospore along with subsequent developmental stages that precede infection.
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Zhang, Peikai, David E. Williams, Logan Stephens, Robert Helps, Irene Patricia Shamini Pushparajah, Jadranka Travas-Sejdic, and Marion Wood. "Microfluidic Biosensors for the Detection of Motile Plant Zoospores." Biosensors 15, no. 3 (February 21, 2025): 131. https://doi.org/10.3390/bios15030131.
Full textAbstract:
Plant pathogen zoospores play a vital role in the transmission of several significant plant diseases, with their early detection being important for effective pathogen management. Current methods for pathogen detection involve labour-intensive specimen collection and laboratory testing, lacking real-time feedback capabilities. Methods that can be deployed in the field and remotely addressed are required. In this study, we have developed an innovative zoospore-sensing device by combining a microfluidic sampling system with a microfluidic cytometer and incorporating a chemotactic response as a means to selectively detect motile spores. Spores of Phytophthora cactorum were guided to swim up a detection channel following a gradient of attractant. They were then detected by a transient change in impedance when they passed between a pair of electrodes. Single-zoospore detection was demonstrated with signal-to-noise ratios of ~17 when a carrying flow was used and ~5.9 when the zoospores were induced to swim into the channel following the gradient of the attractants. This work provides an innovative solution for the selective, sensitive and real-time detection of motile zoospores. It has great potential to be further developed into a portable, remotely addressable, low-cost sensing system, offering an important tool for field pathogen real-time detection applications.
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Miller, Charles E., Robert W. Martin, and Daniel P. Dylewski. "The ultrastructure of plasmodia, sporangia, and cystosori of Ligniera verrucosa (Plasmodiophoromycetes)." Canadian Journal of Botany 63, no. 2 (February 1, 1985): 263–73. http://dx.doi.org/10.1139/b85-030.
Full textAbstract:
The ultrastructure of plasmodia, sporangia, and cystosori of Ligniera verrucosa Maire and Tison is described and compared with that of other plasmodiophorids. Sporangiogenic plasmodia cleave into multilobed sporangia. The contents of each sporangial lobe cleaves to form secondary zoospores, which escape the sporangium by swimming through adjacent lobes after walls between lobes break down. Certain peripherally situated lobes do not form zoospores and, after expelling their undifferentiated contents, function as exit tubes during zoospore emergence. Plasmodia contained several large, membrane-bound vacuoles of unknown function. The taxonomy of the genus Ligniera and its species is discussed. Ligniera is a good and valid taxon.
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Rollins, Lucy, Katie Coats, Marianne Elliott, and Gary Chastagner. "Comparison of Five Detection and Quantification Methods for Phytophthora ramorum in Stream and Irrigation Water." Plant Disease 100, no. 6 (June 2016): 1202–11. http://dx.doi.org/10.1094/pdis-11-15-1380-re.
Full textAbstract:
Propagules of Phytophthora ramorum, the causal agent of sudden oak death (SOD) and ramorum blight, can be recovered from infested stream and nursery irrigation runoff using baiting and filtration methods. Five detection methods, including pear and rhododendron leaf baits, Bottle O’ Bait, filtration, and quantitative polymerase chain reaction (qPCR) performed on zoospores trapped on a filter were compared simultaneously in laboratory assays using lab or creek water spiked with known quantities of P. ramorum zoospores. The detection threshold for each method was determined and methods that could be used to quantify zoospore inoculum were identified. Filtration and qPCR were the most sensitive at detecting low levels of zoospores, followed by wounded rhododendron leaves, rhododendron leaf disks, and pear baits. Filtration, qPCR, and leaf disks were able to quantify P. ramorum zoospores ranging from 2 to 451 direct-plate CFU/liter while wounded leaves and pear baits appeared to be better at detection rather than quantification. The ability to detect and quantify P. ramorum inoculum in water will assist scientists, regulatory agencies, and nursery personnel in assessing the risk of spreading P. ramorum in nurseries and landscape sites where untreated infested water is used for irrigation.
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van de Mortel, Judith E., Ha Tran, Francine Govers, and Jos M. Raaijmakers. "Cellular Responses of the Late Blight Pathogen Phytophthora infestans to Cyclic Lipopeptide Surfactants and Their Dependence on G Proteins." Applied and Environmental Microbiology 75, no. 15 (June 5, 2009): 4950–57. http://dx.doi.org/10.1128/aem.00241-09.
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ABSTRACT Oomycete pathogens cause major yield losses for many crop plants, and their control depends heavily on agrochemicals. Cyclic lipopeptides (CLPs) were recently discovered as a new class of natural compounds with strong activities against oomycetes. The CLP massetolide A (Mass A), produced by Pseudomonas fluorescens, has zoosporicidal activity, induces systemic resistance, and reduces late blight in tomato. To gain further insight into the modes of action of CLPs, the effects of Mass A on pore formation, mycelial growth, sporangium formation, and zoospore behavior were investigated, as was the involvement of G proteins in the sensitivity of Phytophthora infestans to Mass A. The results showed that Mass A induced the formation of transmembrane pores with an estimated size of between 1.2 and 1.8 nm. Dose-response experiments revealed that zoospores were the most sensitive to Mass A, followed by mycelium and cysts. Mass A significantly reduced sporangium formation and caused increased branching and swelling of hyphae. At relatively low concentrations, Mass A induced encystment of zoospores. It had no effect on the chemotactic response of zoospores but did adversely affect zoospore autoaggregation. A loss-of-function transformant of P. infestans lacking the G-protein α subunit was more sensitive to Mass A, whereas a gain-of-function transformant required a higher Mass A concentration to interfere with zoospore aggregation. Results indicate that Mass A disturbs various developmental stages in the life cycle of P. infestans and suggest that the cellular responses of P. infestans to this CLP are, in part, dependent on G-protein signaling.
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Maier, Michelle A., and Tawnya D. Peterson. "Enumeration of Parasitic Chytrid Zoospores in the Columbia River via Quantitative PCR." Applied and Environmental Microbiology 82, no. 13 (April 22, 2016): 3857–67. http://dx.doi.org/10.1128/aem.00084-16.
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ABSTRACTThrough lethal infection, fungal parasites of phytoplankton (“chytrids”) repackage organic material from the large, effectively inedible, colonial diatoms they infect into much smaller zoospores, which are easier for zooplankton to consume. However, their small size and lack of distinguishing morphological features render it difficult to distinguish zoospores from other small flagellates in mixed assemblages in the natural environment. In this study, we developed and tested a method to quantify chytrid zoospores in field studies using quantitative PCR (qPCR) targeting the internal transcribed spacer 2 (ITS2) region within the rRNA gene cluster. To achieve accurate quantification, the assay was designed to be highly specific for a parasite (Rhizophydium planktonicum) of the diatomAsterionella formosa; however, the approach is applicable to additional host-parasite systems. Parasitic zoospores were detected and quantified in the freshwater reaches of the lower Columbia River, as well as in the salt-influenced estuary and river plume. The coincidence between zoospore abundances and a prevalence of small zooplankton during blooms of large, colonial diatoms in the spring suggests that Columbia River zooplankton may be poised to benefit nutritionally from chytrid zoospores, thus providing a mechanism to retain organic carbon within the system and reduce losses to downstream export. We estimate that ∼15% of the carbon biomass tied up in blooms of the dominant diatom species is transformed into zoospores through the parasitic shunt during spring.IMPORTANCEThe small size of the parasitic fungi that infect phytoplankton makes it difficult to identify and quantify them in natural systems. We developed and tested a method to quantify these organisms (chytrid zoospores) using a molecular technique that targets the internal transcribed spacer region within the rRNA gene cluster. Using this method, we quantified the abundance of the motile stage of a specific parasite in the freshwater and saltwater-influenced regions of the Columbia River in the U.S. Pacific Northwest. Parasitic chytrid zoospores were found to be present throughout the year and at higher abundances during the spring, when phytoplankton blooms occur. The presence of these organisms indicates not only that they may be responsible for the death of host phytoplankton cells but that they may also provide a readily available food source to small consumers (zooplankton) in the food web of the Columbia River.
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Taylor, Raymond J., Julie S. Pasche, and Neil C. Gudmestad. "Etiology of a Tuber Rot and Foliar Blight of Potato Caused by Phytophthora nicotianae." Plant Disease 99, no. 4 (April 2015): 474–81. http://dx.doi.org/10.1094/pdis-05-14-0519-re.
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Although Phytophthora nicotianae is not normally considered to be an important pathogen of potato (Solanum tuberosum), intermittent outbreaks of a foliar blight and tuber rot have been reported in the United States over the past 75 years. Due to the sporadic nature of these reports, little is known about the etiology of the disease in potato. However, foliar disease and tuber rots caused by this pathogen are usually centered near areas of standing water in the field and along pivot tracks. Moreover, soil particles adhering to the foliage of infected potato plants suggest that water splash is involved in P. nicotianae dissemination and infection. Soil infestation and water splash dissemination studies were conducted under greenhouse conditions to examine the role that zoospores of P. nicotianae may play in disease on potato. In the soil infestation study, inoculum of P. nicotianae was added to soil at four rates (0.0, 1.0 × 103, 5.0 × 103, and 4.0 × 104 zoospores/ml) and three timings (at planting and 7 and 14 days after planting). Direct infection of aboveground plant tissues was achieved via splash dissemination of inoculum onto potato foliage. All soil infestations significantly reduced emergence, with the exception of the 1.0 × 103 zoospores/ml treatment, and no plants emerged from soil infested with 4.0 ×104 zoospores/ml. Significant reductions in stem number were observed with infestations of 1.0 × 103 and 5.0 × 103 zoospores/ml at planting and 5.0 × 103 zoospores/ml at 7 days after planting. Progeny tuber infections were confirmed with infestations at 1.0 × 103 zoospores/ml at planting and 7 days after planting. Lesions developed on leaflets, petioles, leaf axils, and stems in all water splash dissemination treatments within 3 days of inoculation, significant differences in the lesion number were observed, and disease severity generally was proportional to inoculum concentration. Relative area under the disease progress curve of the 5.0 × 103 and 4.0 × 104 zoospores/ml splash dissemination treatments was significantly greater than the 0.0 zoospore and 1.0 × 103 zoospores/ml treatments. Progeny tuber infections were observed with all water splash dissemination treatments but infection rates did not differ significantly among treatments. These studies confirm the hypothesis that water splash dissemination of P. nicotianae inoculum is a likely means by which infections of this pathogen are initiated in potato.
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Shin, Woongghi, Sung Min Boo, and Joyce E. Longcore. "Entophlyctis apiculata, a chytrid parasite of Chlamydomonas sp. (Chlorophyceae)." Canadian Journal of Botany 79, no. 9 (September 1, 2001): 1083–89. http://dx.doi.org/10.1139/b01-086.
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A chytridialean fungus identified as Entophlyctis apiculata (Braun) Fischer parasitized cells of Chlamydomonas sp. that bloomed in an agricultural pond in Hongsung, Korea, during 1999 and 2000. This is one of the species for which Fischer described the genus Entophlyctis in 1892. Since the segregation of the Spizellomycetales from the Chytridiales confusion has existed as to whether Entophlyctis is a spizellomycetalean or a chytridialean genus. We examined the morphology and development of the Korean E. apiculata with light and transmission electron microscopy. The parasite develops exogenously and has a monocentric, inoperculate zoosporangium. Zoospores within the sporangium contain a single lipid globule associated with a microbody, a rumposome, and a nonflagellated centriole that is parallel and attached by fibers to the kinetosome. These features indicate that E. apiculata is a member of the Chytridiales; however, zoospores were still within the zoosporangium and did not provide sufficient characters to determine the zoospore subtype, which is important for identifying clades within this order.Key words: Chytridiales, pond, Spizellomycetales, ultrastructure, zoospore.
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Heungens, K., and J. L. Parke. "Zoospore Homing and Infection Events: Effects of the Biocontrol Bacterium Burkholderia cepacia AMMDR1 on Two Oomycete Pathogens of Pea (Pisum sativum L.)." Applied and Environmental Microbiology 66, no. 12 (December 1, 2000): 5192–200. http://dx.doi.org/10.1128/aem.66.12.5192-5200.2000.
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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 ofB. cepacia AMMDR1 on Pythium aphanidermatum andAphanomyces euteiches zoospore homing events and on infection of pea seeds or roots. In vitro, B. cepaciaAMMDR1 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 Pythiumzoospores 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 ofAphanomyces zoospores or Aphanomyces root rot incidence. These results suggest that B. cepacia AMMDR1 controlsP. aphanidermatum largely through antibiosis, but competition for zoospore-attracting compounds can contribute to the effect. Differences in suppression of Aphanomyces andPythium are discussed in relation to differences in the ecology of the two pathogens.
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Rollins, Lucy, Marianne Elliott, and Gary Chastagner. "Applying Phytophthora ramorum Inoculum to Hosts: A New Method That Simulates Overhead Irrigation." Plant Health Progress 16, no. 2 (January 2015): 100–106. http://dx.doi.org/10.1094/php-rs-15-0008.
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The inoculum threshold for Phytophthora ramorum in irrigation water required for infection of plant material was investigated using a novel pressurized device designed to deliver zoospore inoculum in a way that simulated certain aspects of overhead irrigation. The measured-inoculum spray applicator (MISA) was made from plastic plumbing parts and worked by spraying measured volumes of pressurized zoospore inoculum onto plant material through an adjustable misting nozzle attached to the bottom of the device. Pressurization and spraying of P. ramorum zoospores through the MISA did not significantly affect zoospore viability or infectivity on wounded and non-wounded detached Rhododendron x ‘Nova Zembla’ leaves under controlled laboratory conditions. An inoculum threshold of 51 zoospores/ml was found for infection of Rhododendron leaves by P. ramorum using regression analysis. The MISA can potentially be used to simulate overhead irrigation in research involving pathogenic Phytophthora spp., and the results of the current research may assist nursery managers, property owners, and regulatory agencies in assessing the risk of using P. ramorum infested water for irrigation within nurseries and private landscapes. Accepted for publication 19 June 2015. Published 26 June 2015.
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Longcore, Joyce E. "Morphology and zoospore ultrastructure of Lacustromyces hiemalis gen. et sp.nov. (Chytridiales)." Canadian Journal of Botany 71, no. 3 (March 1, 1993): 414–25. http://dx.doi.org/10.1139/b93-046.
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As part of a baseline study of chytridiomycete fungi in two Maine lakes, a polycentric, chitinophilic, and heretofore undescribed zoosporic fungus was found. The tubular thallus of Lacustromyces hiemalis gen. et sp.nov. has intercalary thin-walled zoosporangia, has thick-walled resistant sporangia, and does not grow at temperatures greater than 23 °C. Transmission electron microscopy revealed that its zoospores are a variant of the chytridialean type. The microbody – lipid globule complex is of a previously undescribed type, lacking a rumposome or other membrane cisterna and consisting of multiple lipid globules enclosed in a microbody that extends towards the kinetosome. Three kinds of microtubule roots arise near the kinetosome, a root leading to the microbody, a ribosomal root, and a microtubule organizing center that gives rise to microtubules that extend singly into the cytoplasm. Key words: Chytridiales, fungus, Lacustromyces, lake, ultrastructure, zoospore.
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Sadowski, Laura A., and Martha J. Powell. "Cytochemical detection of polysaccharides in zoospores of Aphanomyces euteiches." Canadian Journal of Botany 68, no. 6 (June 1, 1990): 1379–88. http://dx.doi.org/10.1139/b90-176.
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Carbohydrates in thin-sectioned zoospores of the pea root pathogen Aphanomyces euteiches were ultrastructurally localized with the silver methenamine technique. The polysaccharide specificity of localization was verified with minus periodic acid or minus silver methenamine controls, with the sulfhydryl blocker iodoacetate, and with the dialdehyde blockers dimedone and sodium bisulfite. Reaction produce was found on the inner and outer surfaces of the plasma membrane and over the membranes of the water expulsion vacuole system. Inclusions within dense-body vacuoles were covered with reaction product, often in distinct zones. The central core region of K2-bodies, comprising an array of fibers, also contained carbohydrates. Little or no silver methenamine reaction product was found in peripheral vesicles or encystment vesicles, two organelles implicated in cell surface modifications during encystment. This study demonstrates that the cell surface of the unwalled zoospore contains carbohydrates and that the K2-body of A. euteiches, like the K2-body of Saprolegnia ferax, compartmentalizes carbohydrates. We conclude that K2-bodies found in zoospores of two different genera of Oomycetes are homologous organelles. Key words: carbohydrates, zoospore, Aphanomyces, K2-bodies, membranes.
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Zheng, X. B., and W. H. Ko. "Continuing variation in successive asexual generations of Phytophthora cinnamomi following sexual reproduction." Canadian Journal of Botany 74, no. 7 (July 1, 1996): 1181–85. http://dx.doi.org/10.1139/b96-140.
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Colony-type stability of asexual progeny of selfed-oospore cultures of Phytophthora cinnamomi was investigated. Progeny were divided into parental type A, types B to E for those different from type A but with a distinct uniform pattern, and type M for those with the overlapping appearance of two different types. Colonies derived from three successive zoospore generations of isolate P630 were of the same parental A type. However, colonies from oospores of the same isolate consisted of types A, B, C, D, E, and M. Some of the oospore cultures of type A or B and all the type M oospore cultures produced zoospores containing more than one type. Oospore cultures of types C, D, or E that were tested produced zoospores with the same colony type as their respective parent. Among the five cultures randomly selected from asexual progeny produced by oospore isolates P630-21 and P630-6, four displayed continuing variation in colony type in the three to five successive zoospore generations tested. Keywords: asexual variation, continuing variation, Phytophthora cinnamomi, sexual reproduction.
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Newell, Steven Y., and Jack W. Fell. "Do halophytophthoras (marine Pythiaceae) rapidly occupy fallen leaves by intraleaf mycelial growth." Canadian Journal of Botany 73, no. 5 (May 1, 1995): 761–65. http://dx.doi.org/10.1139/b95-083.
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Low estimates (2 ∙ L−1) of concentrations of zoospores of Halophytophthora in mangrove water columns seem counterintuitive when compared with rapid rates of occupation of fallen mangrove leaves (100% frequency of occurrence after 24–30 h). One potential explanation is that lateral extension of mycelium within leaves is rapid after establishment of single zoospores. We tested this hypothesis by exposing single leaves in both mangrove and temperate salt-marsh ecosystems, with the upper half of leaves freely exposed to zoospore contact, and the lower half protected behind 8-μm screening. We found no evidence that mycelial growth within leaves was rapid enough to account for the rapid occupation of freely exposed leaves. Of the four Halophytophthora species commonly found (H. kandeliae, H. masteri, H. spinosa var. spinosa, and H. vesicula), only H. masteri appeared to have substantial capability for its zoospores to pass the screening. In temperate salt-marsh waters, H. kandeliae took the place of H. spinosa as co-occupier of leaves with H. vesicula. Two rare species (H. bahamensis and H. epistomium) originally described from subtropical mangrove environs were found in temperate salt-marsh samples. Key words: oomycotes, oomycetes, Halophytophthora, mangrove, salt marsh.
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Peveling, E., and J. König. "Differences in formation of vegetative cells and their walls in Trebouxia and Pseudotrebouxia as further evidence for the classification of these genera." Lichenologist 17, no. 3 (October 1985): 281–87. http://dx.doi.org/10.1017/s0024282985000366.
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AbstractThe formation of vegetative cells from zoospores and the morphogenesis of the multilayered cell walls during this process was observed in some Trebouxia and Pseudotrebouxia species. In Trebouxia species, e.g. Trebouxia erici, the wall of the vegetative cell is formed around the zoospore while in Pseudotrebouxia species, e.g. Pseudotrebouxia corticola, firstly an autosporangium with its wall is formed then the autosporangium further divides.
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Hardham, A. R., and E. Suzaki. "Glycoconjugates on the surface of spores of the pathogenic fungus Phytophthora cinnamomi studied using fluorescence and electron microscopy and flow cytometry." Canadian Journal of Microbiology 36, no. 3 (March 1, 1990): 183–92. http://dx.doi.org/10.1139/m90-032.
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Glycoconjugates on the surface of zoospores and cysts of the pathogenic fungus Phytophthora cinnamomi have been studied using fluorescein isothiocyanate labelled lectins for fluorescence microscopy and flow cytometry, and ferritin- and gold-labelled lectins for ultrastructural analysis. Of the five lectins used, only concanavalin A (ConA) binds to the surface of the zoospores, including the flagella and water expulsion vacuole. This suggests that of accessible saccharides, glucosyl or mannosyl residues predominate on the outer surface of the zoospore plasma membrane. Early in encystment, a system of flat disc-like cisternae, which underlie the zoospore plasma membrane, vesiculate. These and other small peripheral vesicles quickly disappear. After the induction of encystment, ConA is no longer localised close to the plasma membrane but binds to material loosely associated with the cell surface. Quantitative measurements by flow cytometry indicate that the ConA-binding material is gradually lost from the cell surface. The cyst wall is weakly labelled, but the site of germ tube emergence stains intensely. During the first 2 min after the induction of encystment, material that binds soybean agglutinin, Helix pommatia agglutinin, and peanut agglutinin appears on the surface of the fungal cells. The distribution of this material, rich in galactosyl or N-acetyl-D-galactosaminosyl residues, is initially patchy, but by 5 min the material evenly coats most of the cell surface. Labelling of zoospores in which intracellular sites are accessible indicates that the soybean agglutinin binding material is stored in vesicles that lie beneath the plasma membrane. Quantitation of soybean agglutinin labelling shows that maximum binding occurs 2–3 min after the induction of encystment. Key words: cell surface, flow cytometry, lectins, pathogenic fungi, Phytophthora cinnamomi.
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Bauer, Andreas, and Mirjana Minceva. "Examination of Photo-, Mixo-, and Heterotrophic Cultivation Conditions on Haematococcus pluvialis Cyst Cell Germination." Applied Sciences 11, no. 16 (August 4, 2021): 7201. http://dx.doi.org/10.3390/app11167201.
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The microalgae Haematococcus pluvialis is used for the biotechnological production of astaxanthin. The red carotenoid accumulates in the cytoplasm under unfavorable conditions. Astaxanthin synthesis is associated with the transformation of motile vegetative cells into non-motile cyst cells. In the industrial process, after harvesting, the cyst cells are mechanically disrupted, dried, and finally, astaxanthin is extracted with supercritical CO2. The germination of the cyst cells represents an interesting alternative, replacing the mechanical cyst cell wall disruption. When cyst cells are exposed to favorable growth conditions, germination of the cyst cells occurs and zoospores are released after a certain time. These zoospores show a much weaker cell matrix compared to cyst cells. In this study, germination under phototrophic, mixotrophic, and heterotrophic conditions was examined. Glucose was used as the carbon source for mixotrophic and heterotrophic germination. Applying heterotrophic conditions, up to 80% of the cells were in the zoospore stage 49 h after the start of germination, and extraction yields of up to 50% were achieved using the solvent ethyl acetate for the extraction of astaxanthin from the algal broth containing zoospores. An extraction yield of up to 64% could be achieved by doubling the nitrate concentration and combining mixotrophic and heterotrophic cultivation.