摘要：SummaryMost organisms respond to light. Here, we investigate the origin of metazoan phototransduction by comparing well-characterized opsin-based photosystems in neural animals with those in the spongeAmphimedon queenslandica. Although sponges lack neurons and opsins, they can respond rapidly to light. InAmphimedonlarvae, this is guided by the light-sensing posterior pigment ring. We first use cell-type-specific transcriptomes to reveal that genes that characterize eumetazoan Gt- and Go-mediated photosystems are enriched in the pigment ring. We then apply a suite of signaling pathway agonists and antagonists to swimming larvae exposed to directional light. These experiments implicate metabotropic glutamate receptors, phospholipase-C, protein kinase C, and voltage-gated calcium channels in larval phototaxis; the inhibition of phospholipase-C, a key transducer of the Gq-mediated pathway, completely reverses phototactic behavior. Together, these results are consistent with aneural sponges sharing with neural metazoans an ancestral set of photosignaling pathways.Graphical abstractDisplay OmittedHighlights•Amphimedonlarvae are negatively phototactic but lack neurons and opsins•Sponge larval photosensory cells are enriched in conserved phototransduction genes•Conserved photosignaling pathways appear to be controlling larval phototaxis•Phototactic behavior is reversed by the inhibition of phospholipase-CEvolutionary biology; Evolutionary history; Cell biology
