Abstract
Cryptochromes are flavoprotein photoreceptors with multiple signaling roles during plant de-etiolation and development. Arabidopsis cryptochromes (cry1 and cry2) absorb light through an oxidized flavin (FADox) cofactor which undergoes reduction to both FADH° and FADH− redox states. Since the FADH° redox state has been linked to biological activity, it is important to estimate its concentration formed upon illumination in vivo. Here we model the photocycle of isolated cry1 and cry2 proteins with a three-state kinetic model. Our model fits the experimental data for flavin photoconversion in vitro for both cry1 and cry2, providing calculated quantum yields which are significantly lower in cry1 than for cry2. The model was applied to the cryptochrome photocycle in vivo using biological activity in plants as a readout for FADH° concentration. The fit to the in vivo data provided quantum yields for cry1 and cry2 flavin reduction similar to those obtained in vitro, with decreased cry1 quantum yield as compared to cry2. These results validate our assumption that FADH° concentration correlates with biological activity. This is the first reported attempt at kinetic modeling of the cryptochrome photocycle in relation to macroscopic signaling events in vivo, and thereby provides a theoretical framework to the components of the photocycle that are necessary for cryptochrome response to environmental signals.
Highlights
Plants adapt to their light environment by means of multiple photoreceptors which optimally absorb at different wavelengths of light throughout the visible spectrum
The goal of this study is to apply a simple kinetic model to the cryptochrome photocycle (Figure 1) that can accurately predict the effects of illumination on redox state interconversion in vitro and relate this model to observations on biological activation in vivo
We first apply the model in vitro, to samples of purified isolated cryptochrome which were photoreduced under defined illumination conditions
Summary
Plants adapt to their light environment by means of multiple photoreceptors which optimally absorb at different wavelengths of light throughout the visible spectrum. These include specific photoreceptors absorbing in the blue—UV/A such as cryptochromes (Chaves et al, 2011; Wang et al, 2014) and phototropins (Christie et al, 2015), red/far red light absorbing phytochromes (Burgie and Vierstra, 2014; Xu et al, 2015) and UV-B specific receptors (Jenkins, 2014). The pigments absorb photons at specific wavelengths of light to initiate a primary photochemical reaction These reactions, in turn, trigger changes within the photoreceptor apoprotein leading to the initiation of biological signaling.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
