How did plants develop photosynthesis? The story is really nothing more than a tale of biological thievery. More than a billion years ago, hungry, single-celled eukaryotes gobbled up photosynthetic cyanobacteria, integrating the bacteria’s light-feeding properties into their own biology.

That moment in evolutionary history is important to Distinguished Professor J. Clark Lagarias, Department of Molecular and Cellular Biology, and his colleagues in the College of Biological Sciences, as it marked the origin of chloroplasts, the cellular structures in plants responsible for photosynthesis.

As every high school biology student learns, photosynthesis is the conversion of light energy into chemical energy. The Lagarias Lab studies phytochromes, sensors outside of the chloroplasts which regulate the amount of light harvested for photosynthesis. These light sensors protect the chloroplasts from absorbing too much energy, which can kill the cell.

To understand how light harvesting is controlled in the alga Chlamydomonas reinhardtii, an aquatic relative of plants which lack phytochromes, Lagarias focused on the pigments responsible for the blue-green color of cyanobacteria, which enable phytochromes in plants to sense light.

Publishing in The Plant Cell, Lagarias and his colleagues found that a pigment called biliverdin is essential to light-induced chlorophyll production in the alga. This discovery is helping scientists understand why diverse algae retain these pigments, although many lack phytochromes.