All immune genes identified in A. vulgare are involved in canonical immune pathways (Table 4 and Figure 3): i) pathogen detection including recognition molecules such as the lectins and peroxinectins (PXN) that are able to PND-1186 datasheet distinguish between self and non-self particles and signal transducers; ii) immune cellular responses including opsonization molecules (e.g., PXN and masquerade-like

proteins) inducing phagocytosis and AZD0530 mw cellular encapsulation; iii) immune humoral responses involving clotting and coagulation reactions, production of AMPs, generation of reactive oxygen species, detoxification processes, and the proPhenoloxidase (proPO) cascade; and iv) other pathways connected to immune responses such as antiviral immunity (RNA interference), programmed cell death (apoptosis and autophagy), and cell differentiation such as hematopoiesis [49, 50, HSP inhibitor 59, 60]. Although 40 new genes all involved in immune pathways have been identified, several key genes were lacking (Figure 3). This can be explained by three non-exclusive hypotheses: The relatively low depth of the sequencing effort, the weak annotation (44%) due to divergence between isopods and the other Arthropoda clades, and the absence of some immune genes in isopods. For example, genes encoding important innate immune receptors, such as GNBPs or Toll, and their signal transducers Imd, Dorsal,

Cactus, Relish were known in different crustacean species [47, 49, 61, 62] but were not identified in A. vulgare. PO activity is detected in crustaceans, but isopods such why as chelicerates seem to lack PO enzyme and the corresponding gene [11, 58, 63, 64]. In the same way, the PGRP genes have never been identified in crustacean EST libraries nor in the brine shrimp genome [47], which suggests that these genes could be absent in this clade. A growing number of studies showed that the immune system of Wolbachia-infected animals

is modulated at the molecular level [17, 18, 22]. In A. vulgare, it has recently been shown that Wolbachia impact immune cellular processes [10, 11, 65]. We show here that Wolbachia symbiosis leads to a down-regulation of some A. vulgare immune genes. Indeed, among the candidate genes tested, 72% are down-regulated in whole females, 75% in ovaries and 19% in immune tissues. Among the 46 genes analyzed, no significant differential expression was detected in the immune tissues, whereas the expression of 16 of them was significantly disturbed when Wolbachia were present in whole animals and ovaries. The impacted genes are involved in biological functions such as stress response and detoxification, autophagy, AMP synthesis, pathogen recognition, and proteolytic cascades. Several impacted genes are involved in oxidative stress response. The production of reactive oxygen species (ROS) is one of the first lines of defence against invading microbes.