FLP-15 functions through the GPCR NPR-3 to regulate local and global search behaviours in Caenorhabditis elegans

Foraging is essential for sustenance and well-being of all organisms. The transition from well-fed to food-deprived conditions in C. elegans triggers a localized exploration of the environment characterized by frequent reorientations. However, over time the cumulative frequency of these reorientations decreases, facilitating the transition to global search behaviour. To investigate the genetic regulation of foraging in C. elegans, we conducted a screen of neuropeptide mutants and identified several candidates involved in modulating this behaviour. Among these, neuropeptide FLP-15 emerged as a key regulator of both local and global search behaviours. Our observations revealed that FLP-15 regulates the frequency and duration of reversals during foraging. Further investigation indicated that FLP-15 is expressed in and functions through the I2 pharyngeal neuron via the G-protein coupled receptor NPR-3. Mutants lacking either flp-15 or npr-3 displayed a significant decrease in reversal frequency during local search behaviours. Interestingly, unlike wild-type animals, the reversal frequency in flp-15 and npr-3 mutants did not decrease over time. This study also describes the expression pattern of NPR-3, in a subset of head neurons, predominantly comprising of dopaminergic neurons. This expression pattern highlights a potential link between neuropeptide signalling and dopaminergic modulation of behaviour. Finally, exogenous dopamine supplementation assays revealed that FLP-15 may regulate foraging by modulating dopamine transmission, highlighting a novel neuropeptide-dopamine interaction involved in the control of foraging behaviours.