Curated Optogenetic Publication Database

Abstract: Light is a pivotal environmental signal regulating diverse plant developmental and physiological processes, including seed germination, hypocotyl elongation, phototropism, metabolite biosynthesis, stress resistance, temperature response, and circadian rhythms. Multiple signal transduction pathways of ultraviolet, blue light, and red/far-red light as well as related protein interaction networks in plants have been identified. Deciphering the mechanisms of light perception and signal transduction is of great significance to crop breeding and optogenetic manipulation. Structural biology has profoundly advanced the studies of light signal transduction by elucidating high-resolution three-dimensional (3D) structures of photoreceptors and their downstream signaling components. These studies uncover the molecular basis underlying perception and transduction of different light signals by plants. This review summarizes key structural findings of plant light signal transduction, highlighting the architectures and molecular functions of photoreceptors and associated signaling factors. We also outline the mechanisms underlying photoreceptor activation, inhibition, and regulatory interactions within light signaling networks and discuss the challenges in this field.

Abstract: The blue-light receptor cryptochrome (CRY) in plants undergoes oligomerization to transduce blue-light signals after irradiation, but the corresponding molecular mechanism remains poorly understood. Here, we report the cryogenic electron microscopy structure of a blue-light-activated CRY2 tetramer at a resolution of 3.1 Å, which shows how the CRY2 tetramer assembles. Our study provides insights into blue-light-mediated activation of CRY2 and a theoretical basis for developing regulators of CRYs for optogenetic manipulation.

Abstract: Cryptochromes (CRYs) are blue-light receptors in plants that harbor FAD as a cofactor and regulate various physiological responses. Photoactivated CRYs undergo oligomerization, which increases the binding affinity to downstream signaling partners. Despite decades of research on the activation of CRYs, little is known about how they are inactivated. Binding of blue-light inhibitors of cryptochromes (BICs) to CRY2 suppresses its photoactivation, but the underlying mechanism remains unknown. Here, we report crystal structures of CRY2N (CRY2 PHR domain) and the BIC2-CRY2N complex with resolutions of 2.7 and 2.5 Å, respectively. In the BIC2-CRY2N complex, BIC2 exhibits an extremely extended structure that sinuously winds around CRY2N. In this way, BIC2 not only restrains the transfer of electrons and protons from CRY2 to FAD during photoreduction but also interacts with the CRY2 oligomer to return it to the monomer form. Uncovering the mechanism of CRY2 inactivation lays a solid foundation for the investigation of cryptochrome protein function.