Sweet neurons inhibit texture discrimination by signaling TMC-expressing mechanosensitive neurons in <i>Drosophila</i>.

Abstract

Integration of stimuli of different modalities is an important but incompletely understood process during decision making. Here, we show that <i>Drosophila</i> are capable of integrating mechanosensory and chemosensory information of choice options when deciding where to deposit their eggs. Specifically, females switch from preferring the softer option for egg-laying when both options are sugar free to being indifferent between them when both contain sucrose. Such sucrose-induced indifference between options of different hardness requires functional sweet neurons, and, curiously, the Transmembrane Channel-like (TMC)-expressing mechanosensitive neurons that have been previously shown to promote discrimination of substrate hardness during feeding. Further, axons of sweet neurons directly contact axons of TMC-expressing neurons in the brain and stimulation of sweet neurons increases Ca²⁺ influx into axons of TMC-expressing neurons. These results uncover one mechanism by which <i>Drosophila</i> integrate taste and tactile information when deciding where to deposit their eggs and reveal that TMC-expressing neurons play opposing roles in hardness discrimination in two different decisions.