A Go-type opsin mediates the shadow reflex in the annelid Platynereis dumerilii

• Published in: BMC biology Vol. 16; no. 1; p. 41
• Main Authors: Ayers, Thomas, Tsukamoto, Hisao, Gühmann, Martin, Veedin Rajan, Vinoth Babu, Tessmar-Raible, Kristin
• Format: Journal Article
• Language: English
• Published: London BioMed Central Ltd 18.04.2018; BioMed Central; BMC
• Subjects: annelid; Annelids; behaviour; Gene expression; Genetic aspects; marine; non-visual; Opsins; Photoreceptors; Physiological aspects; Platynereis dumerilii
• ISSN: 1741-7007; 1741-7007
• DOI: 10.1186/s12915-018-0505-8

The presence of photoreceptive molecules outside the eye is widespread among animals, yet their functions in the periphery are less well understood. Marine organisms, such as annelid worms, exhibit a 'shadow reflex', a defensive withdrawal behaviour triggered by a decrease in illumination. Herein, we examine the cellular and molecular underpinnings of this response, identifying a role for a photoreceptor molecule of the G.sub.o-opsin class in the shadow response of the marine bristle worm Platynereis dumerilii. We found Pdu-Go-opsin1 expression in single specialised cells located in adult Platynereis head and trunk appendages, known as cirri. Using gene knock-out technology and ablation approaches, we show that the presence of Go-opsin1 and the cirri is necessary for the shadow reflex. Consistently, quantification of the shadow reflex reveals a chromatic dependence upon light of approximately 500 nm in wavelength, matching the photoexcitation characteristics of the Platynereis Go-opsin1. However, the loss of Go-opsin1 does not abolish the shadow reflex completely, suggesting the existence of a compensatory mechanism, possibly acting through a ciliary-type opsin, Pdu-c-opsin2, with a Lambda.sub.max of approximately 490 nm. We show that a Go-opsin is necessary for the shadow reflex in a marine annelid, describing a functional example for a peripherally expressed photoreceptor, and suggesting that, in different species, distinct opsins contribute to varying degrees to the shadow reflex.