Gene loss and relaxed selection of in vertebrates adapted to low-light environments.

Gene loss is an important mechanism for evolution in low-light or cave environments where visual adaptations often involve a reduction or loss of eyesight. The gene family encodes phospholipases essential for the degradation of organelles in the lens of the eye. These phospholipases translocate to damaged organelle membranes, inducing them to rupture. This rupture is required for lens transparency and is essential for developing a functioning eye. is thought to be responsible for this role in mammals, while is thought to be responsible in other vertebrates. We used a macroevolutionary approach and comparative genomics to examine the origin, loss, synteny and selection of across bony fishes and tetrapods. We showed that (probably ancestral to all bony fish + tetrapods) has been lost in squamates and is significantly degraded in lineages of low-visual-acuity and blind mammals and fishes. Our findings suggest that is important for visual acuity across bony vertebrates, and that its loss through relaxed selection and pseudogenization may have played a role in the repeated evolution of visual systems in low-light environments. Our study sheds light on the importance of gene-loss in trait evolution and provides insights into the mechanisms underlying visual acuity in low-light environments.