From attraction to avoidance: exploring the role of Painless in thermal sensing in a blood-feeding insect

Heat is a key sensory cue for blood-feeding insects, playing a central role in host-seeking and blood-feeding while allowing the avoidance of potentially harmful conditions. The kissing bug Rhodnius prolixus is highly sensitive to thermal stimuli and can detect both heat and infrared radiation (IR) associated with warm-blooded hosts. However, the molecular mechanisms underlying these responses remain poorly understood. This thesis investigates the role of the gene Painless, a TRPA-type receptor, in thermal stimulus detection in R. prolixus. We hypothesize that Painless mediates thermosensory transduction, across different thermal contexts including aversive heat, IR and host-like temperatures. To test this, we combine RNAi with complementary behavioral paradigms evaluating orientation toward heat and IR, proboscis extension responses (PER) elicited by host-range temperatures, and responses to aversive heat. Three experimental groups will be compared: intact insects, insects injected with control dsRNA, and insects in which Painless expression is reduced by RNA interference (RNAi). Comparing responses among groups will allow us to determine whether Painless participates broadly in thermal sensing or whether its contribution depends on temperature range and behavioral context. By integrating behavioral and molecular data, this project aims to clarify Painless' role in thermal sensing and how it shapes attractive, appetitive, or aversive responses in this blood-feeding insect.