The first fireflies glowed green

The common ancestor of modern fireflies lived some 100 million years ago, setting the evolutionary course that resulted in the more than 2,000 species alive today. These insects glow different shades of yellow, green, and orange, depending on the version of the luciferase enzyme they express. This enzyme produces light when it reacts with a small organic molecule called luciferin. A team led by researchers at Chubu University and Nagahama Institute of Bio-Science and Technology has reconstructed the genetic sequence of the luciferase enzyme expressed by the common ancestor of today’s fireflies, using the evolutionary relationships of different firefly species to infer the ancestral sequence. When the researchers made the ancestral protein in the lab, it glowed green (Sci. Adv. 2020, DOI: 10.1126/sciadv.abc5705). The researchers’ analysis of the sequence suggests that the early luciferase came from fatty acyl coenzyme A synthetase, an enzyme involved in fatty acid biosynthesis. As the enzyme acquired mutations that made it glow, it lost its role in synthesizing fatty acids. The researchers believe that luciferase’s first function was to emit light in the larval stage as a warning to potential predators, something some firefly species still do. Later, it played a role in adult insects: attracting potential mates using various colors of light.