title: Genome-wide gene expression in response to parasitoid attack in Drosophila.
abstract: BACKGROUND
  Parasitoids are insect parasites whose larvae develop in the bodies of other insects. The main immune defense against parasitoids is encapsulation of the foreign body by blood cells, which subsequently often melanize. The capsule sequesters and kills the parasite. The molecular processes involved are still poorly understood, especially compared with insect humoral immunity.
  
  
  RESULTS
  We explored the transcriptional response to parasitoid attack in Drosophila larvae at nine time points following parasitism, hybridizing five biologic replicates per time point to whole-genome microarrays for both parasitized and control larvae. We found significantly different expression profiles for 159 probe sets (representing genes), and we classified them into 16 clusters based on patterns of co-expression. A series of functional annotations were nonrandomly associated with different clusters, including several involving immunity and related functions. We also identified nonrandom associations of transcription factor binding sites for three main regulators of innate immune responses (GATA/srp-like, NF-kappaB/Rel-like and Stat), as well as a novel putative binding site for an unknown transcription factor. The appearance or absence of candidate genes previously associated with insect immunity in our differentially expressed gene set was surveyed.
  
  
  CONCLUSIONS
  Most genes that exhibited altered expression following parasitoid attack differed from those induced during antimicrobial immune responses, and had not previously been associated with defense. Applying bioinformatic techniques contributed toward a description of the encapsulation response as an integrated system, identifying putative regulators of co-expressed and functionally related genes. Genome-wide studies such as ours are a powerful first approach to investigating novel genes involved in invertebrate immunity.
authors.affiliation: Centre for Evolutionary Genomics, Department of Biology, University College London, London WC1E 6BT, UK. b.wertheim@ucl.ac.uk
authors.forename: Bregje
authors.initials: B
authors.lastname: Wertheim
authors.forename: Alex R
authors.initials: AR
authors.lastname: Kraaijeveld
authors.forename: Eugene
authors.initials: E
authors.lastname: Schuster
authors.forename: Eric
authors.initials: E
authors.lastname: Blanc
authors.forename: Meirion
authors.initials: M
authors.lastname: Hopkins
authors.forename: Scott D
authors.initials: SD
authors.lastname: Pletcher
authors.forename: Michael R
authors.initials: MR
authors.lastname: Strand
authors.forename: Linda
authors.initials: L
authors.lastname: Partridge
authors.forename: H Charles J
authors.initials: HC
authors.lastname: Godfray
mesh_terms: D000818:Animals; D016000:Cluster Analysis; D019295:Computational Biology; D004330:Drosophila / Q000033:anatomy & histology / Q000235:genetics* / Q000469:parasitology*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D049750:Genome, Insect; D007113:Immunity, Innate / Q000502:physiology; D007814:Larva / Q000033:anatomy & histology / Q000235:genetics / Q000469:parasitology; D020411:Oligonucleotide Array Sequence Analysis; D010271:Parasites / Q000502:physiology; D012045:Regulatory Sequences, Nucleic Acid