Early gene Broad complex plays a key role in regulating the immune response triggered by ecdysone in the Malpighian tubules of Drosophila melanogaster.
In insects, humoral response to injury is accomplished by the production of antimicrobial peptides (AMPs) which are secreted in the hemolymph to eliminate the pathogen. Drosophila Malpighian tubules (MTs), however, are unique immune organs that show constitutive expression of AMPs even in unchallenged conditions and the onset of immune response is developmental stage dependent. Earlier reports have shown ecdysone positively regulates immune response after pathogenic challenge however, a robust response requires prior potentiation by the hormone. Here we provide evidence to show that MTs do not require prior potentiation with ecdysone hormone for expression of AMPs and they respond to ecdysone very fast even without immune challenge, although the different AMPs Diptericin, Cecropin, Attacin, Drosocin show differential expression in response to ecdysone. We show that early gene Broad complex (BR-C) could be regulating the IMD pathway by activating Relish and physically interacting with it to activate AMPs expression. BR-C depletion from Malpighian tubules renders the flies susceptible to infection. We also show that in MTs ecdysone signaling is transduced by EcR-B1 and B2. In the absence of ecdysone signaling the IMD pathway associated genes are down regulated and activation and translocation of transcription factor Relish is also affected.
Cytogenetics Laboratory, Department of Zoology, Banaras Hindu University, Varanasi 221005, Uttar Pradesh, India.
Puja
P
Verma
Cytogenetics Laboratory, Department of Zoology, Banaras Hindu University, Varanasi 221005, Uttar Pradesh, India. Electronic address: madhu@bhu.ac.in.
Madhu G
MG
Tapadia
D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000235:genetics / Q000276:immunology*; D029721:Drosophila Proteins / Q000235:genetics / Q000276:immunology*; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development / Q000276:immunology* / Q000382:microbiology; D004440:Ecdysone / Q000276:immunology* / Q000494:pharmacology; D004926:Escherichia coli / Q000276:immunology; D018507:Gene Expression Regulation, Developmental; D006458:Hemolymph / Q000737:chemistry / Q000276:immunology; D056724:Immunity, Humoral; D007814:Larva / Q000187:drug effects / Q000254:growth & development / Q000276:immunology / Q000382:microbiology; D008317:Malpighian Tubules / Q000737:chemistry / Q000187:drug effects / Q000276:immunology*; D011987:Receptors, Steroid / Q000235:genetics / Q000276:immunology; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000276:immunology*
D023181:Antimicrobial Cationic Peptides; C102117:Br protein, Drosophila; D029721:Drosophila Proteins; D011987:Receptors, Steroid; C101626:Rel protein, Drosophila; D014157:Transcription Factors; C055469:ecdysone receptor; D004440:Ecdysone
Broad complex; Drosophila melanogaster; Ecdysone; Immune response; Malpighian tubules