A FMRFamide-like neuropeptide FLP-12 signaling regulates head locomotive behaviors in Caenorhabditis elegans

Neuropeptides play a critical role in regulating behaviors across organisms, but the precise mechanisms by which neuropeptides orchestrate complex behavioral programs are not fully understood. Here, we show that the FMRFamide-like neuropeptide FLP-12 signaling from the SMB head motor neurons modulates head locomotive behaviors, including stomatal oscillation in Caenorhabditis elegans. lim-4 mutants, in which the SMB neurons are not properly specified, exhibited various head and body locomotive defects, including stomatal oscillation. Chronic activation or inhibition of neuropeptidergic signaling in the SMB motor neurons resulted in a decrease or increase in stomatal oscillation, respectively. The flp-12 neuropeptide gene is expressed and acts in the SMB neurons to regulate head and body locomotion, including stomatal oscillation. Moreover, the frpr-8 G protein-couple receptor (GPCR) and gpa-7 Gα genes are expressed in the AVD command interneurons to relay the FLP-12 signal to mediate stomatal oscillation. Finally, heterologous expression of FRPR-8 either Xenopus oocytes or HEK293T cells conferred FLP-12 induced responses. Taken together, these results indicate that the C. elegans FMRFamide neuropeptide FLP-12 acts as a modulator of stomatal oscillation via the FRPR-8 GPCR and the GPA-7 G-protein.