Fig. 6

The four different types of innate immune signalling pathways recognised in I. elegans. Differentially expressed genes/proteins are represented with red colour boxes. a The Toll immune pathway: exposure to bacterial and fungal peptidoglycans trigger the production of insect peptidoglycan recognition proteins (PGRPs), like PGRP-SA, PGRP-SC1 and PGRP-SD, which in co-operation with Gram-negative binding proteins (GNBPs) like GNBP-1 and GNBP-3, activates proteases Spaetzle (a cytokine-like protein); which in turn activates Toll. Activated Toll activates Dorsal and Dif transcription factors, which then enter into the nucleus, bind to NfkB sites and initiate the transcription of antimicrobial peptides that kill Gram-positive bacteria and fungi by degrading their cell walls. b In the Imd pathway, exposure to meso-diaminopimelic acid (DAP) type peptidoglycan produced by Gram-negative bacteria activates PGRP-LE and PGRP-LC, which in turn activates Imd. Activated Imd further activates Fas-associated death domain (FADD) and death related ced-3/nedd2-like caspase (DREDD), which then activates Relish transcription factor. This enters into the nucleus and induce transcription of antimicrobial peptides detrimental for Gram-negative bacteria. c JAK/STAT cytokine receptor activation caused by unpaired ligands released during infection and injury causes phosphorylation of JAK tyrosine kinase Hopscotch (Hop). The phosphorylated Hop phosphorylate stat 92e, which then dissociate from receptor, dimerize, enters into the nucleus and induces transcription of Thiosester-containing protein genes (Teps) and Turandot (Tot) stress genes. d Prophenol-oxidase cascades are triggered upon exposure to bacterial (Lys and DAP peptidoglycan) and fungal (1, 3-beta-D-glucan) cell wall components. Activation of cascade produces PGPRs (PGRP-S, PGRP-LE and PGRP-1), which generate antimicrobial products like melanin and reactive oxygen species for defence. Refer Fig. 3 and Additional file 1: Sheet 8–11 for differential up-regulation components of immune system