May be involved in strigolactone signaling pathway (By similarity). Essential for plant responses to karrikins, a class of butenolide compounds, structurally similar to strigolactones, released from burning vegetation that stimulate seed germination and enhance seedling photomorphogenesis. Mediates a specific perception of karrikin. Required for the establishment of symbiosis with the arbuscular mycorrhizal fungi (AMF) Rhizophagus irregularis and Gigaspora rosea (PubMed:26680197). Karrikin binding induces a conformational change (By similarity). Component of an intracellular receptor complex involved in the detection of the smoke compound karrikin. Expressed constitutively in all organs (e.g. roots, stems, leaves, panicles and embryos). Loss of responsiveness to and symbiosis with the arbuscular mycorrhizal fungi (AMF) Rhizophagus irregularis and Gigaspora rosea characterized by the absence of physical contact and of characteristic transcriptional responses to fungal signals. Belongs to the AB hydrolase superfamily.