Cry1), a Plant Protein Involved in Blue Light Response*

Cryptochromes are proteins that act as photoreceptors regulating development and the circadian clock in plants. It has been shown that mutations in cryptochromes, specifically AtCry1, alter the functionality of the proteins. These flavoprotein photoreceptors mediate growth, leaf expansion, and floral initiation. They act through blue-light dependent photoreduction of flavin adenine dinucleotide (FAD) via an electron transport chain. In the dark state, the flavin is oxidized and when stimulated with blue light, it is semi-reduced and in the active state which arguably causes protein conformational change and signal transduction. This photoreduction of FAD can be tracked using visible light absorption as the spectra of the oxidized and semi-reduced forms differ. Specifically, the oxidized FAD has a absorption at 450nm and once semi-reduced, the 450nm peak decreases and there is an increase in absorption at 550nm. Mutants studied show significant difference in appearance and plant growth in blue light when compared to native plants. Differences in absorption between mutant and native proteins were used to analyze potential differences in the photochemistry involved in plant growth.