The Jak/Stat pathway mediates disease tolerance during systemic bacterial infection in Drosophila

Abstract

Disease tolerance describes a host’s ability to maintain health independently of the ability to clear microbe loads. However, we currently know little about the mechanisms that underlie disease tolerance or how known mechanisms of tissue damage signalling and repair may contribute to variation in tolerance. The Jak/Stat pathway plays a pivotal role in Drosophila humoral innate immunity, signalling tissue damage and triggering cellular renewal, making it a potential mechanism underlying the disease tolerance phenotype. Here, we show that disrupting the Jak/Stat pathway in Drosophila melanogaster alters disease tolerance during Pseudomonas entomophila systemic infection. Overall, flies with disrupted Jak/Stat show variation in survival that is not explained by variation in pathogen loads. For instance, mutations disrupting the function of ROS-producing dual oxidase (duox) or the negative regulator of Jak/Stat, Socs36E render males less tolerant to systemic bacterial infection but not females. We also investigated whether the negative regulator of Jak/Stat, G9a - which has previously been associated with tolerance of viral infections – is also implicated in tolerance of bacterial infection. While female flies lacking G9a showed higher mortality and reduced bacterial clearance, disease tolerance did not differ between G9a mutants and the wildtype. This suggests that G9a does not affect tolerance during systemic bacterial infection as it appears to do with viral infection. Overall, our findings highlight that Jak/Stat signalling mediates disease tolerance during systemic bacterial infection and that this response differs between males and females. Our work therefore suggests that differences in Jak/Stat mediated disease tolerance may be a potential source of sexually dimorphic response to infection in Drosophila.