Abstract
In flies, grooming serves several purposes, including protection against pathogens and parasites. Previously, we found Escherichia coli or lipopolysaccharides (LPS) can induce grooming behavior via activation of contact chemoreceptors on Drosophila wing. This suggested that specific taste receptors may contribute to this detection. In this study, we examined the perception of commercially available LPS on Drosophila wing chemoreceptors in grooming reflex. Behavioral tests conducted with bitter, sweet and salty gustation such as caffeine, sucrose and salt, using flies carrying a defect in one of their taste receptors related to the detection of bitter molecules (Gr66a, Gr33a), sugars (Gr5a, Gr64f), or salt (IR76b). LPS and tastants of each category were applied to wing sensilla of these taste defectflies and to wild-type Canton Special (CS) flies. Our results indicate that the grooming reflex induced by LPS requires a wide range of gustatory genes, and the inactivation of any of tested genes expressing cells causes a significant reduction of the behavior. This suggests that, while the grooming reflex is strongly regulated by cues perceived as aversive, other sapid cues traditionally related to sweet and salty tastes are also contributing to this behavior.
Highlights
The induction and modification of behavior in Drosophila is dependent on chemical cues from the environment (Depetris-Chauvin et al, 2015)
Our results indicate that the grooming reflex induced by LPS requires a wide range of gustatory genes, and the inactivation of any of tested genes expressing cells causes a significant reduction of the behavior
We further examined the roles of Gr5a, Gr66a, and IR76b which are assumed to be involved in the detection of sugars, bitter substances and salt, respectively (Jiao et al, 2008; Weiss et al, 2011; Zhang et al, 2013)
Summary
The induction and modification of behavior in Drosophila is dependent on chemical cues from the environment (Depetris-Chauvin et al, 2015). The presence of peptidoglycans (PGN) and of unknown impurities contained in sLPS extracts seem to be responsible for triggering grooming, as the response intensity to sLPS is higher than to PGN (Yanagawa et al, 2017) This behavior is quite efficient against microbes which require a physical contact to infect insects (Vega and Kaya, 2012). In our previous study (Yanagawa et al, 2014), only bitter and microbial substances seemed to be important for inducing hygienic behavior (i.e., the grooming reflex) This hypothesis was confirmed by Soldano et al (2016), who reported that TRPA1 cation channels expressed in taste sensilla expressing Gr66a on labellum, regulate sLPS avoidance in D. melanogaster. It is said that Raman information of chemical compositions such as the C]O stretching of amidIindicates the presence a lymph meniscus, whose structure is important to deliver chemical cues to chemoreceptor cells (Valmalette et al, 2015)
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