title: Immunity and other defenses in pea aphids, Acyrthosiphon pisum.
abstract: BACKGROUND
  Recent genomic analyses of arthropod defense mechanisms suggest conservation of key elements underlying responses to pathogens, parasites and stresses. At the center of pathogen-induced immune responses are signaling pathways triggered by the recognition of fungal, bacterial and viral signatures. These pathways result in the production of response molecules, such as antimicrobial peptides and lysozymes, which degrade or destroy invaders. Using the recently sequenced genome of the pea aphid (Acyrthosiphon pisum), we conducted the first extensive annotation of the immune and stress gene repertoire of a hemipterous insect, which is phylogenetically distantly related to previously characterized insects models.
  
  
  RESULTS
  Strikingly, pea aphids appear to be missing genes present in insect genomes characterized to date and thought critical for recognition, signaling and killing of microbes. In line with results of gene annotation, experimental analyses designed to characterize immune response through the isolation of RNA transcripts and proteins from immune-challenged pea aphids uncovered few immune-related products. Gene expression studies, however, indicated some expression of immune and stress-related genes.
  
  
  CONCLUSIONS
  The absence of genes suspected to be essential for the insect immune response suggests that the traditional view of insect immunity may not be as broadly applicable as once thought. The limitations of the aphid immune system may be representative of a broad range of insects, or may be aphid specific. We suggest that several aspects of the aphid life style, such as their association with microbial symbionts, could facilitate survival without strong immune protection.
authors.affiliation: Department of Biology, Emory University, O Wayne Rollins Research Center, 1510 E, Clifton Road NE, Atlanta, GA 30322, USA. nicole.gerardo@emory.edu
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Gerardo
authors.forename: Boran
authors.initials: B
authors.lastname: Altincicek
authors.forename: Caroline
authors.initials: C
authors.lastname: Anselme
authors.forename: Hagop
authors.initials: H
authors.lastname: Atamian
authors.forename: Seth M
authors.initials: SM
authors.lastname: Barribeau
authors.forename: Martin
authors.initials: M
authors.lastname: de Vos
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Duncan
authors.forename: Jay D
authors.initials: JD
authors.lastname: Evans
authors.forename: Toni
authors.initials: T
authors.lastname: Gabaldón
authors.forename: Murad
authors.initials: M
authors.lastname: Ghanim
authors.forename: Adelaziz
authors.initials: A
authors.lastname: Heddi
authors.forename: Isgouhi
authors.initials: I
authors.lastname: Kaloshian
authors.forename: Amparo
authors.initials: A
authors.lastname: Latorre
authors.forename: Andres
authors.initials: A
authors.lastname: Moya
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nakabachi
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Parker
authors.forename: Vincente
authors.initials: V
authors.lastname: Pérez-Brocal
authors.forename: Miguel
authors.initials: M
authors.lastname: Pignatelli
authors.forename: Yvan
authors.initials: Y
authors.lastname: Rahbé
authors.forename: John S
authors.initials: JS
authors.lastname: Ramsey
authors.forename: Chelsea J
authors.initials: CJ
authors.lastname: Spragg
authors.forename: Javier
authors.initials: J
authors.lastname: Tamames
authors.forename: Daniel
authors.initials: D
authors.lastname: Tamarit
authors.forename: Cecilia
authors.initials: C
authors.lastname: Tamborindeguy
authors.forename: Caroline
authors.initials: C
authors.lastname: Vincent-Monegat
authors.forename: Andreas
authors.initials: A
authors.lastname: Vilcinskas
mesh_terms: D000818:Animals; D001042:Aphids / Q000235:genetics* / Q000276:immunology* / Q000382:microbiology; D020869:Gene Expression Profiling; D017344:Genes, Insect; D054884:Host-Pathogen Interactions / Q000276:immunology*; D013312:Stress, Physiological / Q000235:genetics; D013559:Symbiosis / Q000276:immunology