Dataset Information

ROS production during symbiotic infection suppresses pathogenesis-related gene expression.

ABSTRACT: Leguminous plants have exclusive ability to form symbiotic relationship with soil bacteria of the genus Rhizobium. Symbiosis is a complex process that involves multiple molecular signaling activities, such as calcium fluxes, production of reactive oxygen species (ROS) and synthesis of nodulation genes. We analyzed the role of ROS in defense gene expression in Medicago truncatula during symbiosis and pathogenesis. Studies in Arabidopsis thaliana showed that the induction of pathogenesis-related (PR) genes during systemic acquired resistance (SAR) is regulated by NPR1 protein, which resides in the cytoplasm as an oligomer. After oxidative burst and return of reducing conditions, the NPR1 undergoes monomerization and becomes translocated to the nucleus, where it functions in PR genes induction. We show that ROS production is both stronger and longer during symbiotic interactions than during interactions with pathogenic, nonhost or common nonpathogenic soil bacteria. Moreover, root cells inoculated with Sinorhizobium meliloti accumulated ROS in the cytosol but not in vacuoles, as opposed to Pseudomonas putida inoculation or salt stress treatment. Furthermore, increased ROS accumulation by addition of H₂O₂ reduced the PR gene expression, while catalase had an opposite effect, establishing that the PR gene expression is opposite to the level of cytoplasmic ROS. In addition, we show that salicylic acid pretreatment significantly reduced ROS production in root cells during symbiotic interaction.

SUBMITTER: Peleg-Grossman S

PROVIDER: S-EPMC3443923 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:BackgroundParasitic infections can increase susceptibility to bacterial co-infections. This may be true for urogenital schistosomiasis and bacterial urinary tract co-infections (UTI). We previously reported that this co-infection is facilitated by S. haematobium eggs triggering interleukin-4 (IL-4) production and sought to dissect the underlying mechanisms. The interleukin-4-inducing principle from Schistosoma mansoni eggs (IPSE) is one of the most abundant schistosome egg-secreted proteins and binds to IgE on the surface of basophils and mast cells to trigger IL-4 release. IPSE can also translocate into host nuclei using a nuclear localization sequence (NLS) to modulate host transcription. We hypothesized that IPSE is the factor responsible for the ability of S. haematobium eggs to worsen UTI pathogenesis.MethodsMice were intravenously administered a single 25 μg dose of recombinant S. haematobium-derived IPSE, an NLS mutant of IPSE or PBS. Following IPSE exposure, mice were serially weighed and organs analyzed by histology to assess for toxicity. Twenty-four hours after IPSE administration, mice were challenged with the uropathogenic E. coli strain UTI89 by urethral catheterization. Bacterial CFU were measured using urine. Bladders were examined histologically for UTI-triggered pathogenesis and by PCR for antimicrobial peptide and pattern recognition receptor expression.ResultsUnexpectedly, IPSE administration did not result in significant differences in urine bacterial CFU. However, IPSE administration did lead to a significant reduction in UTI-induced bladder pathogenesis and the expression of anti-microbial peptides in the bladder. Despite the profound effect of IPSE on UTI-triggered bladder pathogenesis and anti-microbial peptide production, mice did not demonstrate systemic ill effects from IPSE exposure.ConclusionsOur data show that IPSE may play a major role in S. haematobium-associated urinary tract co-infection, albeit in an unexpected fashion. These findings also indicate that IPSE either works in concert with other IL-4-inducing factors to increase susceptibility of S. haematobium-infected hosts to bacterial co-infection or does not contribute to enhancing vulnerability to this co-infection.

Project description:Aspergillus flavus is a soil-borne saprophyte and an opportunistic pathogen of both humans and plants. This fungus not only causes disease in important food and feed crops such as maize, peanut, cottonseed, and tree nuts but also produces the toxic and carcinogenic secondary metabolites (SMs) known as aflatoxins. Polyamines (PAs) are ubiquitous polycations that influence normal growth, development, and stress responses in living organisms and have been shown to play a significant role in fungal pathogenesis. Biosynthesis of spermidine (Spd) is critical for cell growth as it is required for hypusination-mediated activation of eukaryotic translation initiation factor 5A (eIF5A), and other biochemical functions. The tri-amine Spd is synthesized from the diamine putrescine (Put) by the enzyme spermidine synthase (Spds). Inactivation of spds resulted in a total loss of growth and sporulation in vitro which could be partially restored by addition of exogenous Spd. Complementation of the Δspds mutant with a wild type (WT) A. flavus spds gene restored the WT phenotype. In WT A. flavus, exogenous supply of Spd (in vitro) significantly increased the production of sclerotia and SMs. Infection of maize kernels with the Δspds mutant resulted in a significant reduction in fungal growth, sporulation, and aflatoxin production compared to controls. Quantitative PCR of Δspds mutant infected seeds showed down-regulation of aflatoxin biosynthetic genes in the mutant compared to WT A. flavus infected seeds. Expression analyses of PA metabolism/transport genes during A. flavus-maize interaction showed significant increase in the expression of arginine decarboxylase (Adc) and S-adenosylmethionine decarboxylase (Samdc) genes in the maize host and PA uptake transporters in the fungus. The results presented here demonstrate that Spd biosynthesis is critical for normal development and pathogenesis of A. flavus and pre-treatment of a Δspds mutant with Spd or Spd uptake from the host plant, are insufficient to restore WT levels of pathogenesis and aflatoxin production during seed infection. The data presented here suggest that future studies targeting spermidine biosynthesis in A. flavus, using RNA interference-based host-induced gene silencing approaches, may be an effective strategy to reduce aflatoxin contamination in maize and possibly in other susceptible crops.

Project description:Species of Xenorhabdus and Photorhabdus bacteria form mutualistic associations with Steinernema and Heterorhabditis nematodes, respectively and serve as model systems for studying microbe-animal symbioses. Here, we profiled gene expression of Xenorhabdus koppenhoeferi during their symbiotic persistence in the newly formed infective juveniles of the host nematode Steinernema scarabaei through the selective capture of transcribed sequences (SCOTS). The obtained gene expression profile was then compared with other nematode-bacteria partnerships represented by Steinernema carpocapsae-Xenorhabdus nematophila and Heterorhabditis bacteriophora-Photorhabdus temperata. A total of 29 distinct genes were identified to be up-regulated and 53 were down-regulated in X. koppenhoeferi while in S. scarabaei infective juveniles. Of the identified genes, 8 of the up-regulated and 14 of the down-regulated genes were similarly expressed in X. nematophila during persistence in its host nematode S. carpocapsae. However, only one from each of these up- and down-regulated genes was common to the mutualistic partnership between the bacterium P. temperata and the nematode H. bacteriophora. Interactive network analysis of the shared genes between X. koppenhoeferi and X. nematophila demonstrated that the up-regulated genes were mainly involved in bacterial survival and the down-regulated genes were more related to bacterial virulence and active growth. Disruption of two selected genes pta (coding phosphotransacetylase) and acnB (coding aconitate hydratase) in X. nematophila with shared expression signature with X. koppenhoeferi confirmed that these genes are important for bacterial persistence in the nematode host. The results of our comparative analyses show that the two Xenorhabdus species share a little more than a quarter of the transcriptional mechanisms during persistence in their nematode hosts but these features are quite different from those used by P. temperata bacteria in their nematode host H. bacteriophora.

Dataset Information

ROS production during symbiotic infection suppresses pathogenesis-related gene expression.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets