| Step Number | Component/Molecule | Gene Name | Molecular Function | Role in Pathway |
|---|---|---|---|---|
| 1 | Attractive odorant detected in AWC | not uniquely assigned | External chemical cue sensed by olfactory receptor machinery | Initiates AWC olfactory signaling that ultimately drives chemotaxis and adaptation; specific upstream receptors for many AWC odors remain incompletely defined (pqac-00000027, pqac-00000029) |
| 2 | Odor-responsive GPCR system | multiple candidate GPCRs | G protein-coupled receptor activity | Couples odor detection to intracellular signaling in AWC and activates heterotrimeric G-protein signaling upstream of ODR-3 and guanylyl cyclase regulation (pqac-00000027, pqac-00000029) |
| 3 | G-protein alpha subunit | odr-3 | Gα signaling transducer | Acts downstream of odor-sensing GPCRs and upstream of guanylyl cyclase; in AWC models, odor input alters ODR-3 signaling, which suppresses cyclase activity during stimulation and relieves suppression after odor removal (pqac-00000027, pqac-00000029, pqac-00000030) |
| 4 | Receptor guanylyl cyclase complex | odr-1, daf-11 | Membrane guanylyl cyclase that converts GTP to cGMP | Core cyclase step in AWC; ODR-1 and DAF-11 likely function as a heterodimer, with the intracellular cyclase domain providing the essential signaling output rather than the extracellular domain (pqac-00000003, pqac-00000009, pqac-00000029) |
| 5 | cGMP second messenger | cGMP | Diffusible cyclic nucleotide messenger | Transduces cyclase activity into ion channel gating; cGMP levels are dynamically regulated during odor stimulation and recovery, helping encode ON/OFF response properties and adaptation state (pqac-00000027, pqac-00000030) |
| 6 | Cyclic nucleotide-gated channel | tax-2, tax-4 | cGMP-gated cation channel | Opens in response to cGMP and mediates the primary depolarizing sensory current in AWC, linking cyclase activity to electrical and calcium responses (pqac-00000002, pqac-00000027, pqac-00000029) |
| 7 | Calcium influx and amplification | Ca2+ influx; channel complex includes CNG and downstream VGCCs | Ionic signaling / second messenger | CNG channel opening permits calcium entry and membrane depolarization; odor removal triggers a transient calcium rise in AWC, with feedback control shaping response duration and gain (pqac-00000004, pqac-00000027, pqac-00000030) |
| 8 | Voltage-gated calcium channel amplification | unc-2 and other VGCC components | Voltage-gated Ca2+ entry | Acts downstream of the primary cGMP-gated event to amplify sensory depolarization and calcium signaling in olfactory neurons, contributing to full physiological output (pqac-00000012, pqac-00000027) |
| 9 | cGMP-dependent protein kinase adaptation arm | egl-4 | PKG serine/threonine kinase activated by cGMP | Mediates adaptation across timescales: rapidly tunes AWC response thresholds, later acts on cytoplasmic targets, and after prolonged odor exposure translocates to the nucleus; ODR-1 function is required to keep EGL-4 cytoplasmic before prolonged stimulation (pqac-00000019, pqac-00000020, pqac-00000031) |
| 10 | Nuclear feedback on gene expression | hpl-2, odr-1 | Chromatin-mediated transcriptional repression | After prolonged odor exposure, nuclear EGL-4 phosphorylates HPL-2, which represses transcription of odr-1, creating a negative-feedback loop that contributes to long-term olfactory adaptation/plasticity (pqac-00000020, pqac-00000031) |


*Table: This table summarizes the best-supported AWC olfactory signal transduction pathway centered on ODR-1, from odor detection through cGMP signaling and long-term adaptation. It is useful for mapping where ODR-1 acts enzymatically and how its output is integrated into calcium signaling and feedback regulation.*