title: Pathogen-induced Caenorhabditis elegans developmental plasticity has a hormetic effect on the resistance to biotic and abiotic stresses.
abstract: BACKGROUND
  Phenotypic plasticity, i.e. the capacity to change the phenotype in response to changes in the environment without alteration of the genotype, is important for coping with unstable environments. In spite of the ample evidence that microorganisms are a major environmental component playing a significant role in eukaryotic organisms health and disease, there is not much information about the effect of microorganism-induced developmental phenotypic plasticity on adult animals' stress resistance and longevity.
  
  
  RESULTS
  We examined the consequences of development of Caenorhabditis elegans larvae fed with different bacterial strains on stress resistance and lifespan of adult nematodes. Bacterial strains used in this study were either pathogenic or innocuous to nematodes. Exposure to the pathogen during development did not affect larval survival. However, the development of nematodes on the pathogenic bacterial strains increased lifespan of adult nematodes exposed to the same or a different pathogen. A longer nematode lifespan, developed on pathogens and exposed to pathogens as adults, did not result from an enhanced capacity to kill bacteria, but is likely due to an increased tolerance to the damage inflicted by the pathogenic bacteria. We observed that adult nematodes developed on a pathogen induce higher level of expression of the hsp-16.2 gene and have higher resistance to heat shock than nematodes developed on an innocuous strain. Therefore, the increased resistance to pathogens could be, at least partially, due to the early induction of the heat shock response in nematodes developed on pathogens. The lifespan increase is controlled by the DBL-1 transforming growth factor beta-like, DAF-2/DAF-16 insulin-like, and p38 MAP kinase pathways. Therefore, the observed modulation of adult nematode lifespans by developmental exposure to a pathogen is likely a genetically controlled response.
  
  
  CONCLUSIONS
  Our study shows that development on pathogens has a hormetic effect on adult nematodes, as it results in increased resistance to different pathogens and to heat shock. Such developmental plasticity of C. elegans nematodes, which are self-fertilizing homozygous animals producing offspring with negligible genetic variation, could increase the probability of survival in changing environments.
authors.affiliation: Laboratory of Evolutive, Medical and Molecular Genetics, Inserm U1001, Université Paris Descartes, Sorbonne Paris Cité, 156 rue de Vaugirard, Paris, 75730 cedex 15, France.
authors.forename: Magali
authors.initials: M
authors.lastname: Leroy
authors.forename: Thomas
authors.initials: T
authors.lastname: Mosser
authors.forename: Xavier
authors.initials: X
authors.lastname: Manière
authors.forename: Diana Fernández
authors.initials: DF
authors.lastname: Alvarez
authors.forename: Ivan
authors.initials: I
authors.lastname: Matic
mesh_terms: D000818:Animals; D001419:Bacteria / Q000472:pathogenicity*; D017173:Caenorhabditis elegans / Q000235:genetics / Q000382:microbiology* / Q000502:physiology*; D018869:Heat-Shock Response; D059165:Hormesis; D007814:Larva / Q000382:microbiology / Q000502:physiology; D008136:Longevity / Q000502:physiology; D010641:Phenotype; D015398:Signal Transduction / Q000502:physiology*; D013312:Stress, Physiological