Intestinal lipid droplets as novel mediators of host-pathogen interaction in<i>Drosophila</i>

Abstract

Lipid droplets (LDs) are lipid carrying multifunctional organelles, which might also interact with pathogens and influence the host immune response. However, the exact nature of these interactions remains currently unexplored. Here we show that systemic infection of Drosophila adult flies with non-pathogenic E. coli, the extracellular bacterial pathogen P. luminescens or the facultative intracellular pathogen P. asymbiotica results in intestinal steatosis marked by lipid accumulation in the midgut. Accumulation of LDs in the midgut also correlates with increased whole-body lipid levels characterized by increased expression of genes regulating lipogenesis. The lipid enriched midgut further displays reduced expression of enteroendocrine secreted hormone, Tachykinin. The observed lipid accumulation requires the Gram-negative cell wall pattern recognition molecule PGRP-LC, but not PGRP-LE, for the humoral immune response. Altogether, our findings indicate that Drosophila LDs are inducible organelles, which can serve as marker for inflammation and depending on the nature of the challenge they can dictate the outcome of the infection.