An entomopathogenic bacterium, Xenorhabdus nematophila, inhibits the expression of an antibacterial peptide, cecropin, of the beet armyworm, Spodoptera exigua

Ji, Dongjin; Kim, Yonggyun

doi:10.1016/j.jinsphys.2004.03.005

Cited by 92 publications

(68 citation statements)

References 26 publications

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“…The cellular response is dampened through the killing of haemocytes within 3 hours of infection, probably by the toxic effects of cytolysin, lipopolysaccharide, toxins and fimbrial subunits 56 . The humoral response can also be suppressed by repressing AMP gene expression through a mechanism that remains to be characterized 57 . In a similar way, Pseudomonas aeruginosa can suppress D. melanogaster defence responses by limiting AMP gene expression when injected into the fly haemolymph 58 , using a mechanism that also remains to be characterized.…”

Section: Box 2 | Insect Immune Responsementioning

confidence: 99%

Bacterial strategies to overcome insect defences

2008

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| Recent genetic and molecular analyses have revealed how several strategies enable bacteria to persist and overcome insect immune defences. Genetic and genomic tools that can be used with Drosophila melanogaster have enabled the characterization of the pathways that are used by insects to detect bacterial invaders and combat infection. Conservation of bacterial virulence factors and insect immune repertoires indicates that there are common strategies of host invasion and pathogen eradication. Long-term interactions of bacteria with insects might ensure efficient dissemination of pathogens to other hosts, including humans. R E V I E W S302 | APRIL 2008 | voLUME 6 www.nature.com/reviews/micro

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Section: Box 2 | Insect Immune Responsementioning

confidence: 99%

Bacterial strategies to overcome insect defences

2008

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“…In nature, X. nematophila forms a mutualistic alliance with the nematode Steinernema carpocapsae, which is the vector that carries the bacterium into insects (23,72). When X. nematophila is experimentally injected into insects in the absence of the nematode, the bacterium evades and modulates insect immunity, and host death typically occurs within 48 h (19,37,54).…”

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confidence: 99%

Xenorhabdus nematophila lrhAIs Necessary for Motility, Lipase Activity, Toxin Expression, and Virulence inManduca sextaInsects

et al. 2008

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The gram-negative insect pathogen Xenorhabdus nematophila possesses potential virulence factors including an assortment of toxins, degradative enzymes, and regulators of these compounds. Here, we describe the lysR-like homolog A (lrhA) gene, a gene required by X. nematophila for full virulence in Manduca sexta insects. In several other gram-negative bacteria, LrhA homologs are transcriptional regulators involved in the expression (typically repression) of virulence factors. Based on phenotypic and genetic evidence, we report that X. nematophila LrhA has a positive effect on transcription and expression of certain potential virulence factors, including a toxin subunit-encoding gene, xptD1. Furthermore, an lrhA mutant lacks in vitro lipase activity and has reduced swimming motility compared to its wild-type parent. Quantitative PCR revealed that transcript levels of flagellar genes, a lipase gene, and xptD1 were significantly lower in the lrhA mutant than in the wild type. In addition, lrhA itself is positively regulated by the global regulator Lrp. This work establishes a role for LrhA as a vital component of a regulatory hierarchy necessary for X. nematophila pathogenesis and expression of surface-localized and secreted factors. Future research is aimed at identifying and characterizing virulence factors within the LrhA regulon.

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“…In contrast, Xenorhabdus phoPQ mutants show only sensitivity against AMPs, but not loss of virulence, suggesting that LPS modification is not required for adaptive resistance (Goodrich-Blair et al, 2007). Interestingly, X. nematophilus suppresses the expression of AMPs by an unknown mechanism (Ji et al, 2004;Park, 2007), which appears to be controlled by the master regulator Lrp (Cowles et al, 2007 Recently, Eleftherianos and co-workers have shown that Photorhabdus produces a small-molecule antibiotic stilbene (ST) that acts as an inhibitor of phenoloxidase (PO) in the insect host M. sexta. Inactivation of the Photorhabdus gene stlA, which encodes an enzyme that produces cinnamic acid, a key precursor for production of ST, eliminates ST production and PO inhibitory activity.…”

Section: Xenorhabdus and Photorhabdusmentioning

confidence: 99%

The Diversity of Insect-bacteria Interactions and its Applications for Disease Control

Sánchez-Contreras

Vlisidou

2008

Biotechnology and Genetic Engineering Reviews

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Prokaryotic microorganisms are widespread in all environments on Earth, establishing diverse interactions with many eukaryotic taxa, including insects. These associations may be symbiotic, pathogenic and vectoring. Independently of the type of interaction, each association starts with the adhesion of the microorganism to the host, entry and "invasion" of the host, then progresses to establishment and dissemination within the host, by avoiding host immune responses, and concludes with transmission back to the environment or to a new host. Advances in genomics and genetics have allowed the dissection of these processes and provided important information on the elements driving the shaping of the members of each association. Furthermore, many mechanisms involved in the establishment of the associations have been scrutinised, along with the development of new methods for the management of insect populations.

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An entomopathogenic bacterium, Xenorhabdus nematophila, inhibits the expression of an antibacterial peptide, cecropin, of the beet armyworm, Spodoptera exigua

Cited by 92 publications

References 26 publications

Bacterial strategies to overcome insect defences

Bacterial strategies to overcome insect defences

Xenorhabdus nematophila lrhAIs Necessary for Motility, Lipase Activity, Toxin Expression, and Virulence inManduca sextaInsects

The Diversity of Insect-bacteria Interactions and its Applications for Disease Control

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