Genomic Blueprints of Vision: A Comparative History of Rhodopsin Evolution and Phototransduction

Department of Zoology, Dyal Singh College, University of Delhi, Delhi, India This email address is being protected from spambots. You need JavaScript enabled to view it. , This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Light is the fundamental signal for living entities as life on Earth is ultimately sustained by light energy. Many animals have evolved complex sensory mechanisms to utilize light cues for regulating homeostatic systems such as eyesight and the circadian clock. Organisms adapt to diverse lighting by modifying visual-pigment subtypes and their spectral tuning. These changes affect both color perception and dim-light vision. Through the lens of Comparative Genomics, evolution of opsins acts as a bridge between molecular genetics and ecological adaptation. Opsins are a diverse family of G-protein coupled receptors (GPCRs) that serve as the fundamental molecular interface between light and biological signaling. Rhodopsin is the 7-helical G-coupled receptor transmembrane protein. It also contains 11-cis-retinal, bound to the opsin protein, primarily absorbs light and responsible for scotopic vision in dim light conditions. This study compared Rhodopsin gene at gene sequence level, coding region and protein level among the twenty -six selected organisms from diverse groups including a set of model organisms such as Drosophila melanogaster, Danio rerio, Xenopus laevis, Rattus norvegicus, Gallus gallus, Macaca mulatta, Pan troglodyte and Homo sapiens. The sequence alignment studies show percentage similarities across the genomes and derive different functional annotations that exhibit a diverse role for Rhodopsin. Further the phylogenetic analysis shows how they evolved over the time. The comparative genomic analysis of rhodopsin across diverse organisms effectively demonstrates how evolutionary pressures shape genetic architecture to meet specific environmental demands. Rhodopsin plays a vital role in studying GPCRs vividly, mutations in rhodopsin lead to diseases like Retinitis Pigmentosa and Congenital Stationary Night Blindness which disrupts normal vision and also affect the circadian rhythm, dysregulation causing sleeping disorders. They serve as valuable biomarkers for the early retinal degeneration and detection of neurodegenerative diseases such as Alzheimer’s and Parkinson’s.