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Ralfudo Ehlers - One of the best experts on this subject based on the ideXlab platform.
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applying inbreeding hybridization and mutagenesis to improve oxidative stress tolerance and longevity of the entomopathogenic nematode Heterorhabditis Bacteriophora
Journal of Invertebrate Pathology, 2017Co-Authors: Nanette Hope Sumaya, Ralfudo Ehlers, Temesgen Addis, Riddhi Gohil, Christopher Okolo, Verena Doerfler, Carlos MolinaAbstract:Abstract Poor shelf-life and sensitivity to environmental stress of entomopathogenic nematodes (EPNs) are traits, which deserve attention for improvement. Recently, a strong positive correlation between oxidative stress tolerance and longevity of Heterorhabditis Bacteriophora dauer juveniles (DJs) has been reported. In this study, the improvement of H. Bacteriophora DJ longevity was achieved by hybridization and mutagenesis. A hybrid pool deriving from two oxidative stress tolerant and long-living parental strains was generated. This hybrid AU1 × HU2 survived 2.6 days and 18 days longer than its best parent under oxidative stress and control conditions, respectively. In addition to the natural genetic variability, an EMS-mutant pool (M-OXI) with high longevity was generated and one of the derived mutagenized inbred lines (MOX-IL6) survived 5.8 days and 28.4 days longer than its donor line (IL3) under oxidative stress and control conditions, respectively. A genetic cross between the mutagenized inbred line and its donor line (MOX-IL × IL3) still survived 2.5 days and 18.5 days longer than the donor line under oxidative stress and control conditions, respectively. Concerning virulence and reproductive potential, trade-off effects were not observed as a result of hybridization and mutagenesis. These results underline the potential of classical genetic approaches for trait improvement in the nematode H. Bacteriophora.
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influence of bacterial density and mating on life history traits of Heterorhabditis Bacteriophora
Nematology, 2016Co-Authors: Temesgen Addis, Ralfudo Ehlers, Shiferaw Demissie, Olaf StrauchAbstract:Heterorhabditis Bacteriophora , associated with Photorhabdus luminescens , is commonly used against insect pests. Dauer juveniles (DJ) develop into self-fertilising hermaphrodites that lay eggs until juveniles hatch inside the uterus and feed on the body content of the mother ( endotokia matricida ). The life history traits of H. Bacteriophora were studied at 2.5 × 10 9 , 5 × 10 9 , 10 × 10 9 and 20 × 10 9 cells ml −1 of P. luminescens at 25°C using a hanging drop technique. The number of offspring produced per hermaphrodite increased from 50 at 2.5 × 10 9 cells ml −1 to 269 at 20 × 10 9 cells ml −1 of P. luminescens . The bacterial density did not influence the beginning of endotokia matricida , hermaphrodite death, DJ release from the maternal carcass and the percentage of juveniles obtained through endotokia matricida . Mating of automictic females could not increase offspring production and survival. Endotokia matricida is an obligatory developmental step in H. Bacteriophora .
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selective breeding for desiccation tolerance in liquid culture provides genetically stable inbred lines of the entomopathogenic nematode Heterorhabditis Bacteriophora
Applied Microbiology and Biotechnology, 2013Co-Authors: Samuel Anbesse, Nanette Hope Sumaya, Olaf Strauch, Anna Verena Dorfler, Ralfudo EhlersAbstract:The entomopathogenic nematode (EPN) Heterorhabditis Bacteriophora is used in biological plant protection to control pest insects. In the past, several attempts targeted at an enhancement of the desiccation tolerance of EPN by genetic selection in order to improve their storage stability. The subsequent loss of improved beneficial traits after release of selection pressure has often been reported. In order to stabilize progress of selective breeding, selection during liquid culturing was tested against propagation in host insects. After release of the selection pressure, the tolerance was monitored over additional reproductive cycles in vivo and in vitro to compare the stability of the trait. Furthermore, it was tested whether the virulence of the selected strains would be impaired. Exposure to desiccation stress prior to propagation, in vivo or in vitro, both resulted in increasing desiccation tolerance. When selection pressure was released, the gained tolerance was lost again during in vivo production, whereas the tolerance was maintained at a high level when EPNs were cultured in liquid culture. In Heterorhabditis sp., liquid culture conditions produce highly homozygous, genetically stable inbred lines. The investigation provides easily applicable methods to improve and stabilize beneficial traits of heterorhabditid EPNs through selective breeding in liquid culture. Compared to nematodes from in vivo propagation, production in liquid media yielded EPN of higher virulence.
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Heat tolerance among different strains of the entomopathogenic nematode Heterorhabditis Bacteriophora
BioControl, 2010Co-Authors: John Mukuka, Olaf Strauch, Lieven Waeyenberge, Nicole Viaene, Maurice Moens, Ralfudo EhlersAbstract:Quality of biological control products based on entomopathogenic nematodes can be severely damaged due to exposure to high temperature surpassing 40°C. The study screened 36 natural populations and 18 hybrid or inbred strains of Heterorhabditis Bacteriophora for their response to high temperature. Nematodes were tested with or without prior adaptation to heat at 35°C for 3 h. Five strains of H. indica and one of H. megidis were also included. Molecular identification using nuclear ribosomal DNA sequences confirmed the designation to the three Heterorhabditis spp. The mean tolerated temperature ranged from 33.3°C to 40.1°C for non-adapted and from 34.8°C to 39.2°C for adapted strain populations. H. indica was the most tolerant, followed by H. Bacteriophora and H. megidis . No correlation was recorded between tolerance assessed with and without adaptation to heat, implying that different genes are involved. Correlation between heat tolerance and mean annual temperature at place of origin of the strains was weak. A high variability in tolerance among strains and the relatively high heritability ( h ² = 0.68) for the adapted heat tolerance recorded for H. Bacteriophora provide an excellent foundation for future selective breeding with the objective to enhance heat tolerance of H. Bacteriophora .
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variability in desiccation tolerance among different strains of the entomopathogenic nematode Heterorhabditis Bacteriophora
Nematology, 2010Co-Authors: John Mukuka, Olaf Strauch, Ralfudo EhlersAbstract:The shelf life of biological control products based on the entomopathogenic nematode Heterorhabditis Bacteriophora is rather short. In order to prolong shelf life, the metabolism of nematodes during storage must be reduced. This can be achieved by means of desiccation of the infective third-stage dauer juveniles (DJ). The tolerance can be increased by an adaptation to moderate desiccation conditions. Previous investigations indicate that the heritability of the desiccation tolerance is high, justifying a genetic selection for enhanced tolerance. This investigation screened the desiccation tolerance of 43 strains of Heterorhabditis spp. and 18 hybrid/inbred strains of H. Bacteriophora . Dehydrating conditions measured as water activity ( a w values) were produced by treating DJ with different concentrations of the non-ionic polymer poly(ethylene glycol) 600. Significant inter-specific variation was recorded between nematode strains and species. The mean tolerated a w value (MW 50 ) ranged from 0.90 to 0.95 for non-adapted and 0.67 to 0.99 for adapted nematode populations. For selective breeding, only the 10% most tolerant individuals would be used. The lowest a w value tolerated by 10% of a population (MW 10 ) ranged from of 0.845 to 0.932 for non-adapted nematode populations and 0.603 to 0.950 for adapted nematode populations. Adaptation significantly increased the desiccation tolerance and a weak correlation was recorded for tolerance with and without adaptations. The most tolerant nematode strains will form the basis for the foundation of a parental stock produced by cross-breeding and following genetic selection for enhanced tolerance. Thus, this investigation is another milestone on the road to domestication of H. Bacteriophora for commercial use in sustainable pest management.
Randy Gaugler - One of the best experts on this subject based on the ideXlab platform.
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A lover and a fighter: the genome sequence of an entomopathogenic nematode Heterorhabditis Bacteriophora.
PLoS ONE, 2013Co-Authors: Xiaodong Bai, Randy Gaugler, Todd A Ciche, Byron J Adams, Paul W Sternberg, Kwi Suk Kim, Sandra W Clifton, John Spieth, Richard K Wilson, Parwinder S GrewalAbstract:Heterorhabditis Bacteriophora are entomopathogenic nematodes that have evolved a mutualism with Photorhabdus luminescens bacteria to function as highly virulent insect pathogens. The nematode provides a safe harbor for intestinal symbionts in soil and delivers the symbiotic bacteria into the insect blood. The symbiont provides virulence and toxins, metabolites essential for nematode reproduction, and antibiotic preservation of the insect cadaver. Approximately half of the 21,250 putative protein coding genes identified in the 77 Mbp high quality draft H. Bacteriophora genome sequence were novel proteins of unknown function lacking homologs in Caenorhabditis elegans or any other sequenced organisms. Similarly, 317 of the 603 predicted secreted proteins are novel with unknown function in addition to 19 putative peptidases, 9 peptidase inhibitors and 7 C-type lectins that may function in interactions with insect hosts or bacterial symbionts. The 134 proteins contained mariner transposase domains, of which there are none in C. elegans, suggesting an invasion and expansion of mariner transposons in H. Bacteriophora. Fewer Kyoto Encyclopedia of Genes and Genomes Orthologies in almost all metabolic categories were detected in the genome compared with 9 other sequenced nematode genomes, which may reflect dependence on the symbiont or insect host for these functions. The H. Bacteriophora genome sequence will greatly facilitate genetics, genomics and evolutionary studies to gain fundamental knowledge of nematode parasitism and mutualism. It also elevates the utility of H. Bacteriophora as a bridge species between vertebrate parasitic nematodes and the C. elegans model.
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transcriptomic analysis of the entomopathogenic nematode Heterorhabditis Bacteriophora tto1
BMC Genomics, 2009Co-Authors: Xiaodong Bai, Randy Gaugler, Todd A Ciche, Saskia A Hogenhout, Byron J Adams, Paul W Sternberg, Sandra W Clifton, John Spieth, Richard K Wilson, Parwinder S GrewalAbstract:The entomopathogenic nematode Heterorhabditis Bacteriophora and its symbiotic bacterium, Photorhabdus luminescens, are important biological control agents of insect pests. This nematode-bacterium-insect association represents an emerging tripartite model for research on mutualistic and parasitic symbioses. Elucidation of mechanisms underlying these biological processes may serve as a foundation for improving the biological control potential of the nematode-bacterium complex. This large-scale expressed sequence tag (EST) analysis effort enables gene discovery and development of microsatellite markers. These ESTs will also aid in the annotation of the upcoming complete genome sequence of H. Bacteriophora. A total of 31,485 high quality ESTs were generated from cDNA libraries of the adult H. Bacteriophora TTO1 strain. Cluster analysis revealed the presence of 3,051 contigs and 7,835 singletons, representing 10,886 distinct EST sequences. About 72% of the distinct EST sequences had significant matches (E value < 1e-5) to proteins in GenBank's non-redundant (nr) and Wormpep190 databases. We have identified 12 ESTs corresponding to 8 genes potentially involved in RNA interference, 22 ESTs corresponding to 14 genes potentially involved in dauer-related processes, and 51 ESTs corresponding to 27 genes potentially involved in defense and stress responses. Comparison to ESTs and proteins of free-living nematodes led to the identification of 554 parasitic nematode-specific ESTs in H. Bacteriophora, among which are those encoding F-box-like/WD-repeat protein theromacin, Bax inhibitor-1-like protein, and PAZ domain containing protein. Gene Ontology terms were assigned to 6,685 of the 10,886 ESTs. A total of 168 microsatellite loci were identified with primers designable for 141 loci. A total of 10,886 distinct EST sequences were identified from adult H. Bacteriophora cDNA libraries. BLAST searches revealed ESTs potentially involved in parasitism, RNA interference, defense responses, stress responses, and dauer-related processes. The putative microsatellite markers identified in H. Bacteriophora ESTs will enable genetic mapping and population genetic studies. These genomic resources provide the material base necessary for genome annotation, microarray development, and in-depth gene functional analysis.
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expressed sequence tag analysis of gene representation in insect parasitic nematode Heterorhabditis Bacteriophora
Journal of Parasitology, 2007Co-Authors: Xiaodong Bai, Randy Gaugler, Todd A Ciche, Parwinder S Grewal, Saskia A Hogenhout, Byron J Adams, Paul W SternbergAbstract:We compared Heterorhabditis Bacteriophora GPS11 expressed sequence tags (ESTs) to the ESTs of animal-parasitic, human-parasitic, plant-parasitic, and free-living nematodes. We identified 127 previously nondescribed ESTs of which 119 had homologs in ESTs and 8 had homologs in proteins of free-living nematodes. These ESTs were assigned putative functions in transcription, signal transduction, cell cycle control, metabolism, information processing, and cellular processes, thereby providing better insight into H. Bacteriophora metabolism, sex determination, and signal transduction. We also identified 36 H. Bacteriophora ESTs that had significant similarities to ESTs of parasitic nematodes, but not to ESTs or proteins of free-living nematodes species. Among these are the ESTs encoding a centrin, an ankyrin-repeat containing protein, and a nuclear hormone receptor. Our analysis also revealed that parasitic nematode-specific ESTs in this H. Bacteriophora data set had more homologs in animal-parasitic nematodes than those parasitizing humans or plants.
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source of trait deterioration in entomopathogenic nematodes Heterorhabditis Bacteriophora and steinernema carpocapsae during in vivo culture
Nematology, 2006Co-Authors: Anwar L Bilgrami, Randy Gaugler, David I Shapiroilan, Byron J AdamsAbstract:The stability of traits important for biological control was studied in the entomopathogenic nematode-bacteria complexes Heterorhabditis Bacteriophora and Steinernema carpocapsae . Five experimental lines of each species were subcultured for 20 serial passages in Galleria mellonella larvae to assess trait stability. Subculturing impaired performance of both H. Bacteriophora and S. carpocapsae . Virulence, heat tolerance and fecundity deteriorated in all H. Bacteriophora experimental lines, and four out of five experimental lines deteriorated in host-finding ability. All S. carpocapsae experimental lines deteriorated in heat tolerance and nictation, and four out of five experimental lines declined for reproductive capacity, whereas virulence declined in two experimental lines. Determination of whether trait deterioration was due to changes in nematode, bacteria, or both symbiotic partners was tested by exchanging nematodes or bacteria from control populations with nematodes or bacteria from the most deteriorated experimental lines and assessing trait recovery. The source of deterioration varied according to trait, but only the bacterial partner played a role in trait reductions for every trait and species, whereas the nematode was the main source only for S. carpocapsae nictation. These results emphasise the important role each symbiotic partner plays in the stability and expression of beneficial traits.
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stabilization of beneficial traits in Heterorhabditis Bacteriophora through creation of inbred lines
Biological Control, 2005Co-Authors: Cheng Bai, Randy Gaugler, David I Shapiroilan, Keith R HopperAbstract:Abstract Serial culturing of organisms used for biological pest suppression often leads to detrimental genetic changes and loss of utility. We established that genetically homozygous inbred lines can deter beneficial trait decline in the entomopathogenic nematode, Heterorhabditis Bacteriophora . Three inbred lines and the foundation population were serially cultured in the insect host, Galleria mellonella . Trait stability was evaluated by comparing serially cultured with non-cultured populations. Laboratory data indicated that serial culture of the foundation population (16 passages) resulted in more than a 30% loss in traits deemed beneficial for biological pest suppression i.e., virulence to an insect host ( Diaprepes abbreviatus ), reproductive capacity, heat tolerance (at 38 °C), and host-seeking ability. In contrast, the three inbred lines were impervious to decline in all beneficial traits. A greenhouse test targeting D. abbreviatus provided additional evidence that the biocontrol efficacy of the inbred lines remained stable during serial culture. Our results indicate that genetic factors played an important role in trait change, and creation of inbred lines may be a useful technique for maintaining beneficial traits.
Todd A Ciche - One of the best experts on this subject based on the ideXlab platform.
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A lover and a fighter: the genome sequence of an entomopathogenic nematode Heterorhabditis Bacteriophora.
PLoS ONE, 2013Co-Authors: Xiaodong Bai, Randy Gaugler, Todd A Ciche, Byron J Adams, Paul W Sternberg, Kwi Suk Kim, Sandra W Clifton, John Spieth, Richard K Wilson, Parwinder S GrewalAbstract:Heterorhabditis Bacteriophora are entomopathogenic nematodes that have evolved a mutualism with Photorhabdus luminescens bacteria to function as highly virulent insect pathogens. The nematode provides a safe harbor for intestinal symbionts in soil and delivers the symbiotic bacteria into the insect blood. The symbiont provides virulence and toxins, metabolites essential for nematode reproduction, and antibiotic preservation of the insect cadaver. Approximately half of the 21,250 putative protein coding genes identified in the 77 Mbp high quality draft H. Bacteriophora genome sequence were novel proteins of unknown function lacking homologs in Caenorhabditis elegans or any other sequenced organisms. Similarly, 317 of the 603 predicted secreted proteins are novel with unknown function in addition to 19 putative peptidases, 9 peptidase inhibitors and 7 C-type lectins that may function in interactions with insect hosts or bacterial symbionts. The 134 proteins contained mariner transposase domains, of which there are none in C. elegans, suggesting an invasion and expansion of mariner transposons in H. Bacteriophora. Fewer Kyoto Encyclopedia of Genes and Genomes Orthologies in almost all metabolic categories were detected in the genome compared with 9 other sequenced nematode genomes, which may reflect dependence on the symbiont or insect host for these functions. The H. Bacteriophora genome sequence will greatly facilitate genetics, genomics and evolutionary studies to gain fundamental knowledge of nematode parasitism and mutualism. It also elevates the utility of H. Bacteriophora as a bridge species between vertebrate parasitic nematodes and the C. elegans model.
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transcriptional profiling of trait deterioration in the insect pathogenic nematode Heterorhabditis Bacteriophora
BMC Genomics, 2009Co-Authors: Bishwo N Adhikari, Todd A Ciche, Xiaodong Bai, Parwinder S Grewal, Chin Yo Lin, Adler R Dillman, John M Chaston, David I ShapiroilanAbstract:Background: The success of a biological control agent depends on key traits, particularly reproductive potential, environmental tolerance, and ability to be cultured. These traits can deteriorate rapidly when the biological control agent is reared in culture. Trait deterioration under laboratory conditions has been widely documented in the entomopathogenic nematode (EPN) Heterorhabditis Bacteriophora (Hb) but the specific mechanisms behind these genetic processes remain unclear. This research investigates the molecular mechanisms of trait deterioration of two experimental lines of Hb, an inbred line (L5M) and its original parental line (OHB). We generated transcriptional profiles of two experimental lines of Hb, identified the differentially expressed genes (DEGs) and validated their differential expression in the deteriorated line. Results: An expression profiling study was performed between experimental lines L5M and OHB of Hb with probes for 15,220 ESTs from the Hb transcriptome. Microarray analysis showed 1,185 DEGs comprising of 469 down- and 716 up-regulated genes in trait deteriorated nematodes. Analysis of the DEGs showed that trait deterioration involves massive changes of the transcripts encoding enzymes involved in metabolism, signal transduction, virulence and longevity. We observed a pattern of reduced expression of enzymes related to primary metabolic processes and induced secondary metabolism. Expression of sixteen DEGs in trait deteriorated nematodes was validated by quantitative reverse transcription-PCR (qRT-PCR) which revealed similar expression kinetics for all the genes tested as shown by microarray. Conclusion: As the most closely related major entomopathogen to C. elegans, Hb provides an attractive near-term application for using a model organism to better understand interspecies interactions and to enhance our understanding of the mechanisms underlying trait deterioration in biological control agents. This information could also be used to improve the beneficial traits of biological control agents and better understand fundamental aspects of nematode parasitism and mutualism.
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transcriptomic analysis of the entomopathogenic nematode Heterorhabditis Bacteriophora tto1
BMC Genomics, 2009Co-Authors: Xiaodong Bai, Randy Gaugler, Todd A Ciche, Saskia A Hogenhout, Byron J Adams, Paul W Sternberg, Sandra W Clifton, John Spieth, Richard K Wilson, Parwinder S GrewalAbstract:The entomopathogenic nematode Heterorhabditis Bacteriophora and its symbiotic bacterium, Photorhabdus luminescens, are important biological control agents of insect pests. This nematode-bacterium-insect association represents an emerging tripartite model for research on mutualistic and parasitic symbioses. Elucidation of mechanisms underlying these biological processes may serve as a foundation for improving the biological control potential of the nematode-bacterium complex. This large-scale expressed sequence tag (EST) analysis effort enables gene discovery and development of microsatellite markers. These ESTs will also aid in the annotation of the upcoming complete genome sequence of H. Bacteriophora. A total of 31,485 high quality ESTs were generated from cDNA libraries of the adult H. Bacteriophora TTO1 strain. Cluster analysis revealed the presence of 3,051 contigs and 7,835 singletons, representing 10,886 distinct EST sequences. About 72% of the distinct EST sequences had significant matches (E value < 1e-5) to proteins in GenBank's non-redundant (nr) and Wormpep190 databases. We have identified 12 ESTs corresponding to 8 genes potentially involved in RNA interference, 22 ESTs corresponding to 14 genes potentially involved in dauer-related processes, and 51 ESTs corresponding to 27 genes potentially involved in defense and stress responses. Comparison to ESTs and proteins of free-living nematodes led to the identification of 554 parasitic nematode-specific ESTs in H. Bacteriophora, among which are those encoding F-box-like/WD-repeat protein theromacin, Bax inhibitor-1-like protein, and PAZ domain containing protein. Gene Ontology terms were assigned to 6,685 of the 10,886 ESTs. A total of 168 microsatellite loci were identified with primers designable for 141 loci. A total of 10,886 distinct EST sequences were identified from adult H. Bacteriophora cDNA libraries. BLAST searches revealed ESTs potentially involved in parasitism, RNA interference, defense responses, stress responses, and dauer-related processes. The putative microsatellite markers identified in H. Bacteriophora ESTs will enable genetic mapping and population genetic studies. These genomic resources provide the material base necessary for genome annotation, microarray development, and in-depth gene functional analysis.
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cell invasion and matricide during photorhabdus luminescens transmission by Heterorhabditis Bacteriophora nematodes
Applied and Environmental Microbiology, 2008Co-Authors: Todd A Ciche, Kwi Suk Kim, Bettina Kaufmanndaszczuk, Ken C Q Nguyen, David H HallAbstract:Many animals and plants have symbiotic relationships with beneficial bacteria. Experimentally tractable models are necessary to understand the processes involved in the selective transmission of symbiotic bacteria. One such model is the transmission of the insect-pathogenic bacterial symbionts Photorhabdus spp. by Heterorhabditis Bacteriophora infective juvenile (IJ)-stage nematodes. By observing egg-laying behavior and IJ development, it was determined that IJs develop exclusively via intrauterine hatching and matricide (i.e., endotokia matricida). By transiently exposing nematodes to fluorescently labeled symbionts, it was determined that symbionts infect the maternal intestine as a biofilm and then invade and breach the rectal gland epithelium, becoming available to the IJ offspring developing in the pseudocoelom. Cell- and stage-specific infection occurs again in the pre-IJ pharyngeal intestinal valve cells, which helps symbionts to persist as IJs develop and move to a new host. Synchronous with nematode development are changes in symbiont and host behavior (e.g., adherence versus invasion). Thus, Photorhabdus symbionts are maternally transmitted by an elaborate infectious process involving multiple selective steps in order to achieve symbiont-specific transmission.
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expressed sequence tag analysis of gene representation in insect parasitic nematode Heterorhabditis Bacteriophora
Journal of Parasitology, 2007Co-Authors: Xiaodong Bai, Randy Gaugler, Todd A Ciche, Parwinder S Grewal, Saskia A Hogenhout, Byron J Adams, Paul W SternbergAbstract:We compared Heterorhabditis Bacteriophora GPS11 expressed sequence tags (ESTs) to the ESTs of animal-parasitic, human-parasitic, plant-parasitic, and free-living nematodes. We identified 127 previously nondescribed ESTs of which 119 had homologs in ESTs and 8 had homologs in proteins of free-living nematodes. These ESTs were assigned putative functions in transcription, signal transduction, cell cycle control, metabolism, information processing, and cellular processes, thereby providing better insight into H. Bacteriophora metabolism, sex determination, and signal transduction. We also identified 36 H. Bacteriophora ESTs that had significant similarities to ESTs of parasitic nematodes, but not to ESTs or proteins of free-living nematodes species. Among these are the ESTs encoding a centrin, an ankyrin-repeat containing protein, and a nuclear hormone receptor. Our analysis also revealed that parasitic nematode-specific ESTs in this H. Bacteriophora data set had more homologs in animal-parasitic nematodes than those parasitizing humans or plants.
Parwinder S Grewal - One of the best experts on this subject based on the ideXlab platform.
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effect of soil management on Heterorhabditis Bacteriophora gps11 persistence and biological control in a vegetable production system
Biological Control, 2014Co-Authors: Harit K Bal, Parwinder S Grewal, Nuris M Acosta, Zhiqiang Cheng, Hannah Whitehead, Casey W HoyAbstract:Abstract Soil habitat conditions that promote abundance and persistence of entomopathogenic nematodes (EPNs) might be encouraged by reduced tillage and compost amendments. We hypothesized that altered soil management with reduced tillage, cover crops (clover and barley), and compost (100 kg of N/ha), would increase survival and biocontrol services of EPNs, compared with conventional management. Field trials were conducted at the Ohio Agricultural Research and Development Center Muck Crops Research Station, Huron County, OH in 2010 and 2011. Plots were planted with carrots. EPNs, Heterorhabditis Bacteriophora GPS11, were released and their survival was compared between the two soil management regimes by sampling over a period of 8 weeks using in situ bait traps containing Galleria mellonella. Repeated measures analysis of variance did not show significant differences between the two soil management regimes in the pattern of H. Bacteriophora survival over time or during any evaluation in either year, except 2 weeks after cadaver application in 2010 when the EPN population was significantly greater in the conventional than in the alternative soil management regime. Although treatment effects were generally not significant, statistically significant increase in nematode population densities between the 2 years of the study, despite generally poor weather conditions following EPN release in the second year, provide encouraging evidence that populations of these biological control agents could increase in vegetable production fields. However, longer periods may be required for clearly distinguishable increase in EPN population density, persistence, and biological control services in the alternative soil management treatments.
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A lover and a fighter: the genome sequence of an entomopathogenic nematode Heterorhabditis Bacteriophora.
PLoS ONE, 2013Co-Authors: Xiaodong Bai, Randy Gaugler, Todd A Ciche, Byron J Adams, Paul W Sternberg, Kwi Suk Kim, Sandra W Clifton, John Spieth, Richard K Wilson, Parwinder S GrewalAbstract:Heterorhabditis Bacteriophora are entomopathogenic nematodes that have evolved a mutualism with Photorhabdus luminescens bacteria to function as highly virulent insect pathogens. The nematode provides a safe harbor for intestinal symbionts in soil and delivers the symbiotic bacteria into the insect blood. The symbiont provides virulence and toxins, metabolites essential for nematode reproduction, and antibiotic preservation of the insect cadaver. Approximately half of the 21,250 putative protein coding genes identified in the 77 Mbp high quality draft H. Bacteriophora genome sequence were novel proteins of unknown function lacking homologs in Caenorhabditis elegans or any other sequenced organisms. Similarly, 317 of the 603 predicted secreted proteins are novel with unknown function in addition to 19 putative peptidases, 9 peptidase inhibitors and 7 C-type lectins that may function in interactions with insect hosts or bacterial symbionts. The 134 proteins contained mariner transposase domains, of which there are none in C. elegans, suggesting an invasion and expansion of mariner transposons in H. Bacteriophora. Fewer Kyoto Encyclopedia of Genes and Genomes Orthologies in almost all metabolic categories were detected in the genome compared with 9 other sequenced nematode genomes, which may reflect dependence on the symbiont or insect host for these functions. The H. Bacteriophora genome sequence will greatly facilitate genetics, genomics and evolutionary studies to gain fundamental knowledge of nematode parasitism and mutualism. It also elevates the utility of H. Bacteriophora as a bridge species between vertebrate parasitic nematodes and the C. elegans model.
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purl gene expression affects biofilm formation and symbiotic persistence of photorhabdus temperata in the nematode Heterorhabditis Bacteriophora
Microbiology, 2011Co-Authors: Parwinder S GrewalAbstract:Extensive studies of the well-known legume and rhizobium symbiosis model system suggest that the purine metabolic pathway plays a key role in microbe–plant interactions, although the exact mechanism is unknown. Here, we report the impact of a key purine metabolic gene, purL, on the symbiotic interaction between the bacterium Photorhabdus temperata and its nematode partner Heterorhabditis Bacteriophora. Real-time PCR assays showed that the purL gene was upregulated in P. temperata in the nematode infective juvenile compared with artificial media. Mutation of the purL gene by in-frame deletion dramatically decreased the capacity of the bacterium to persist in infective juveniles and its ability to form biofilm in vitro. It was further demonstrated that purL gene expression was positively related to bacterial biofilm formation and the symbiotic persistence of the bacterium in nematode infective juveniles. A ΔpurL mutant lost the ability to support infective juvenile formation in the media which weakly supported biofilm formation, suggesting that a critical level of biofilm formation is required by the bacteria to support infective juvenile formation and thus establish their partnership. In addition, the defects in both biofilm formation and symbiotic ability due to the disruption of the purL gene could be partially restored by the addition of 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), an intermediate of the purine biosynthesis pathway. Overall, these data indicate that the purine metabolic pathway is important in microbe–animal symbioses, and that it may influence symbiotic interactions at the level of biofilm formation.
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transcriptional profiling of trait deterioration in the insect pathogenic nematode Heterorhabditis Bacteriophora
BMC Genomics, 2009Co-Authors: Bishwo N Adhikari, Todd A Ciche, Xiaodong Bai, Parwinder S Grewal, Chin Yo Lin, Adler R Dillman, John M Chaston, David I ShapiroilanAbstract:Background: The success of a biological control agent depends on key traits, particularly reproductive potential, environmental tolerance, and ability to be cultured. These traits can deteriorate rapidly when the biological control agent is reared in culture. Trait deterioration under laboratory conditions has been widely documented in the entomopathogenic nematode (EPN) Heterorhabditis Bacteriophora (Hb) but the specific mechanisms behind these genetic processes remain unclear. This research investigates the molecular mechanisms of trait deterioration of two experimental lines of Hb, an inbred line (L5M) and its original parental line (OHB). We generated transcriptional profiles of two experimental lines of Hb, identified the differentially expressed genes (DEGs) and validated their differential expression in the deteriorated line. Results: An expression profiling study was performed between experimental lines L5M and OHB of Hb with probes for 15,220 ESTs from the Hb transcriptome. Microarray analysis showed 1,185 DEGs comprising of 469 down- and 716 up-regulated genes in trait deteriorated nematodes. Analysis of the DEGs showed that trait deterioration involves massive changes of the transcripts encoding enzymes involved in metabolism, signal transduction, virulence and longevity. We observed a pattern of reduced expression of enzymes related to primary metabolic processes and induced secondary metabolism. Expression of sixteen DEGs in trait deteriorated nematodes was validated by quantitative reverse transcription-PCR (qRT-PCR) which revealed similar expression kinetics for all the genes tested as shown by microarray. Conclusion: As the most closely related major entomopathogen to C. elegans, Hb provides an attractive near-term application for using a model organism to better understand interspecies interactions and to enhance our understanding of the mechanisms underlying trait deterioration in biological control agents. This information could also be used to improve the beneficial traits of biological control agents and better understand fundamental aspects of nematode parasitism and mutualism.
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transcriptomic analysis of the entomopathogenic nematode Heterorhabditis Bacteriophora tto1
BMC Genomics, 2009Co-Authors: Xiaodong Bai, Randy Gaugler, Todd A Ciche, Saskia A Hogenhout, Byron J Adams, Paul W Sternberg, Sandra W Clifton, John Spieth, Richard K Wilson, Parwinder S GrewalAbstract:The entomopathogenic nematode Heterorhabditis Bacteriophora and its symbiotic bacterium, Photorhabdus luminescens, are important biological control agents of insect pests. This nematode-bacterium-insect association represents an emerging tripartite model for research on mutualistic and parasitic symbioses. Elucidation of mechanisms underlying these biological processes may serve as a foundation for improving the biological control potential of the nematode-bacterium complex. This large-scale expressed sequence tag (EST) analysis effort enables gene discovery and development of microsatellite markers. These ESTs will also aid in the annotation of the upcoming complete genome sequence of H. Bacteriophora. A total of 31,485 high quality ESTs were generated from cDNA libraries of the adult H. Bacteriophora TTO1 strain. Cluster analysis revealed the presence of 3,051 contigs and 7,835 singletons, representing 10,886 distinct EST sequences. About 72% of the distinct EST sequences had significant matches (E value < 1e-5) to proteins in GenBank's non-redundant (nr) and Wormpep190 databases. We have identified 12 ESTs corresponding to 8 genes potentially involved in RNA interference, 22 ESTs corresponding to 14 genes potentially involved in dauer-related processes, and 51 ESTs corresponding to 27 genes potentially involved in defense and stress responses. Comparison to ESTs and proteins of free-living nematodes led to the identification of 554 parasitic nematode-specific ESTs in H. Bacteriophora, among which are those encoding F-box-like/WD-repeat protein theromacin, Bax inhibitor-1-like protein, and PAZ domain containing protein. Gene Ontology terms were assigned to 6,685 of the 10,886 ESTs. A total of 168 microsatellite loci were identified with primers designable for 141 loci. A total of 10,886 distinct EST sequences were identified from adult H. Bacteriophora cDNA libraries. BLAST searches revealed ESTs potentially involved in parasitism, RNA interference, defense responses, stress responses, and dauer-related processes. The putative microsatellite markers identified in H. Bacteriophora ESTs will enable genetic mapping and population genetic studies. These genomic resources provide the material base necessary for genome annotation, microarray development, and in-depth gene functional analysis.
David I Shapiroilan - One of the best experts on this subject based on the ideXlab platform.
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transcriptional profiling of trait deterioration in the insect pathogenic nematode Heterorhabditis Bacteriophora
BMC Genomics, 2009Co-Authors: Bishwo N Adhikari, Todd A Ciche, Xiaodong Bai, Parwinder S Grewal, Chin Yo Lin, Adler R Dillman, John M Chaston, David I ShapiroilanAbstract:Background: The success of a biological control agent depends on key traits, particularly reproductive potential, environmental tolerance, and ability to be cultured. These traits can deteriorate rapidly when the biological control agent is reared in culture. Trait deterioration under laboratory conditions has been widely documented in the entomopathogenic nematode (EPN) Heterorhabditis Bacteriophora (Hb) but the specific mechanisms behind these genetic processes remain unclear. This research investigates the molecular mechanisms of trait deterioration of two experimental lines of Hb, an inbred line (L5M) and its original parental line (OHB). We generated transcriptional profiles of two experimental lines of Hb, identified the differentially expressed genes (DEGs) and validated their differential expression in the deteriorated line. Results: An expression profiling study was performed between experimental lines L5M and OHB of Hb with probes for 15,220 ESTs from the Hb transcriptome. Microarray analysis showed 1,185 DEGs comprising of 469 down- and 716 up-regulated genes in trait deteriorated nematodes. Analysis of the DEGs showed that trait deterioration involves massive changes of the transcripts encoding enzymes involved in metabolism, signal transduction, virulence and longevity. We observed a pattern of reduced expression of enzymes related to primary metabolic processes and induced secondary metabolism. Expression of sixteen DEGs in trait deteriorated nematodes was validated by quantitative reverse transcription-PCR (qRT-PCR) which revealed similar expression kinetics for all the genes tested as shown by microarray. Conclusion: As the most closely related major entomopathogen to C. elegans, Hb provides an attractive near-term application for using a model organism to better understand interspecies interactions and to enhance our understanding of the mechanisms underlying trait deterioration in biological control agents. This information could also be used to improve the beneficial traits of biological control agents and better understand fundamental aspects of nematode parasitism and mutualism.
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source of trait deterioration in entomopathogenic nematodes Heterorhabditis Bacteriophora and steinernema carpocapsae during in vivo culture
Nematology, 2006Co-Authors: Anwar L Bilgrami, Randy Gaugler, David I Shapiroilan, Byron J AdamsAbstract:The stability of traits important for biological control was studied in the entomopathogenic nematode-bacteria complexes Heterorhabditis Bacteriophora and Steinernema carpocapsae . Five experimental lines of each species were subcultured for 20 serial passages in Galleria mellonella larvae to assess trait stability. Subculturing impaired performance of both H. Bacteriophora and S. carpocapsae . Virulence, heat tolerance and fecundity deteriorated in all H. Bacteriophora experimental lines, and four out of five experimental lines deteriorated in host-finding ability. All S. carpocapsae experimental lines deteriorated in heat tolerance and nictation, and four out of five experimental lines declined for reproductive capacity, whereas virulence declined in two experimental lines. Determination of whether trait deterioration was due to changes in nematode, bacteria, or both symbiotic partners was tested by exchanging nematodes or bacteria from control populations with nematodes or bacteria from the most deteriorated experimental lines and assessing trait recovery. The source of deterioration varied according to trait, but only the bacterial partner played a role in trait reductions for every trait and species, whereas the nematode was the main source only for S. carpocapsae nictation. These results emphasise the important role each symbiotic partner plays in the stability and expression of beneficial traits.
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stabilization of beneficial traits in Heterorhabditis Bacteriophora through creation of inbred lines
Biological Control, 2005Co-Authors: Cheng Bai, Randy Gaugler, David I Shapiroilan, Keith R HopperAbstract:Abstract Serial culturing of organisms used for biological pest suppression often leads to detrimental genetic changes and loss of utility. We established that genetically homozygous inbred lines can deter beneficial trait decline in the entomopathogenic nematode, Heterorhabditis Bacteriophora . Three inbred lines and the foundation population were serially cultured in the insect host, Galleria mellonella . Trait stability was evaluated by comparing serially cultured with non-cultured populations. Laboratory data indicated that serial culture of the foundation population (16 passages) resulted in more than a 30% loss in traits deemed beneficial for biological pest suppression i.e., virulence to an insect host ( Diaprepes abbreviatus ), reproductive capacity, heat tolerance (at 38 °C), and host-seeking ability. In contrast, the three inbred lines were impervious to decline in all beneficial traits. A greenhouse test targeting D. abbreviatus provided additional evidence that the biocontrol efficacy of the inbred lines remained stable during serial culture. Our results indicate that genetic factors played an important role in trait change, and creation of inbred lines may be a useful technique for maintaining beneficial traits.