Modern agriculture relies on crops that have been carefully tailored for environments by selective breeding. Phytochromes are attractive targets for crop improvement efforts aimed to enhance seed germination, seedling establishment, plant architecture and flowering time. The overall goal of this research is to understand the structural basis of both photosensory and regulatory functions of phytochromes from cyanobacteria to plants. Such basic knowledge will be leveraged for development of new strategies to alter the light responsiveness of agriculturally significant plant species. For example, our discovery of dominant photochemically uncoupled phytochrome alleles holds significant promise for crop improvement. Such plant-derived reagents may overcome environmental concerns while addressing the pressing need for increased food production on a finite amount of arable land needed to nourish the growing world population.