The Cryptochromes: Blue Light Photoreceptors in Plants and Animals

Wang

Proc. Natl. Acad. Sci. U.S.A.

et al. 2013

Significance Plants rely on many different types of photoreceptors to control light responses, but the molecular mechanisms underlying the coaction of different photoreceptors that regulate the same light response remains unclear. This study demonstrates a mechanism of the photoreceptor coaction. In Arabidopsis , the blue-light receptor cryptochrome 2 interacts with and activates the transcription factor CRYPTOCHROME-INTERACTING basic helix–loop–helix 1 (CIB1). It was found that CIB1 protein is degraded in the absence of blue light and that the light–oxygen–voltage-domain F-box blue-light receptor ZEITLUPE mediates blue-light suppression of CIB1 degradation.

mentioning

confidence: 99%

Arabidopsis CRY2 and ZTL mediate blue-light regulation of the transcription factor CIB1 by distinct mechanisms

Wang

Proc. Natl. Acad. Sci. U.S.A.

et al. 2013

Physiol Mol Biol Plants

“…Arabidopsis is the sole plant species for which the full set of photoreceptor genes has been characterized (Demarsy and Fankhauser 2009;Inoue et al 2010;Nagatani 2010;Chaves et al 2011). In Solanaceae, photoperception and light signaling have been mainly investigated in tomato, tobacco and potato (Perrotta et al 2000;Weller et al 2001;Fernández et al 2005;Rutitzky et al 2009).…”

Section: Discussionmentioning

confidence: 99%

“…In higher plants, it is perceived by a complex system of photoreceptor molecules: the blue (B) and ultraviolet-A (UV-A) light sensing cryptochromes (cry) (Chaves et al 2011) and phototropins (phot) (Inoue et al 2010) and the red (R)/far red (FR) phytochrome (phy) receptors (Nagatani 2010). More recently, a novel family of B photoreceptors has been described in Arabidopsis thaliana : the Zeitlupe (ZTL)/ Flavin-binding Kelch repeat F-box protein (FKF1)/LOV Kelch Protein (LKP2) family (Demarsy and Fankhauser 2009).…”

Section: Introductionmentioning

confidence: 99%

A reverse genetics approach identifies novel mutants in light responses and anthocyanin metabolism in petunia

Berenschot

Quecini

2013

Flower color and plant architecture are important commercially valuable features for ornamental petunias (Petunia x hybrida Vilm.). Photoperception and light signaling are the major environmental factors controlling anthocyanin and chlorophyll biosynthesis and shadeavoidance responses in higher plants. The genetic regulators of these processes were investigated in petunia by in silico analyses and the sequence information was used to devise a reverse genetics approach to probe mutant populations. Petunia orthologs of photoreceptor, light-signaling components and anthocyanin metabolism genes were identified and investigated for functional conservation by phylogenetic and protein motif analyses. The expression profiles of photoreceptor gene families and of transcription factors regulating anthocyanin biosynthesis were obtained by bioinformatic tools. Two mutant populations, generated by an alkalyting agent and by gamma irradiation, were screened using a phenotype-independent, sequence-based method by high-throughput PCR-based assay. The strategy allowed the identification of novel mutant alleles for anthocyanin biosynthesis (CHALCONE SYNTHASE ) and regulation (PH4), and for light signaling (CONSTANS ) genes.

“…1 Attention has recently focussed on the flavoprotein cryptochrome which has been proposed as the primary sensory molecule by which migratory birds detect the direction of the Earth's magnetic field. [2][3][4][5] Blue-light excitation of the flavin adenine dinucleotide (FAD) chromophore in cryptochrome is thought to trigger intra-protein electron transfers along a triad of tryptophan (Trp) residues to give a stabilised, charge-separated FAD-Trp radical pair.…”

mentioning

confidence: 99%

“…Moving to microscopy-based fluorescence 2 | J. Name., 2012, 00, [1][2][3] This journal is © The Royal Society of Chemistry 2012 measurements will also be crucial for attempts to measure MFEs on single molecules. To determine whether cryptochromes are fit for purpose as biological compass sensors, it will be necessary to characterise their directional responses to weak external magnetic fields.…”

mentioning

confidence: 99%

Fluorescence-detected magnetic field effects on radical pair reactions from femtolitre volumes

et al. 2015

We show that the effects of applied magnetic fields on radical pair reactions can be sensitively measured from sample volumes as low as ~100 femtolitres using total internal reflection fluorescence microscopy. Development of a fluorescence-based microscope method is likely to be a key step in further miniaturisation that will allow detection of magnetic field effects on single molecules.Flavins -tricyclic aza-aromatic compounds -occur widely in Nature and perform a variety of biological functions, many of which involve electron transfer. 1 Attention has recently focussed on the flavoprotein cryptochrome which has been proposed as the primary sensory molecule by which migratory birds detect the direction of the Earth's magnetic field. 2-5 Blue-light excitation of the flavin adenine dinucleotide (FAD) chromophore in cryptochrome is thought to trigger intra-protein electron transfers along a triad of tryptophan (Trp) residues to give a stabilised, charge-separated FAD-Trp radical pair. 6-9 Transient absorption studies 10 have shown that coherent interconversion of the electronic singlet and triplet states of the radical pair gives rise to long lived states of the protein whose quantum yields can be modified by applied magnetic fields via the well-established radical pair mechanism. 11,12 Studies of the magnetic sensitivity of cryptochromes are currently constrained by the relatively high protein concentrations and large sample volumes required for absorption-based spectroscopy and by the photo-degradation caused by the intense laser pulses often needed for such measurements. 13,14 Cryptochromes -in particular the vertebrate proteins -are difficult to express recombinantly in large quantities and tend to aggregate in concentrated solution. Further in vitro studies of their magnetic responses will require a detection method compatible with much smaller quantities of protein, the obvious choice being fluorescence.Fluorescence has been used extensively to monitor magnetic field effects (MFEs) on the photochemistry of small organic radicals. In appropriate, usually non-aqueous, solvents singlet but not triplet radical pairs can often recombine to form an exciplex whose fluorescence provides a convenient and sensitive probe of the magnetic response. [15][16][17][18] Effective though such an approach has proved, it is manifestly inapplicable when the radical pair cannot recombine to form a luminescent state. Many radical pairs, including flavin-Trp, do not form excited molecular complexes and cryptochromes have no other electronically excited states that can be populated from the FAD-Trp radical pair.However, flavins do have fluorescent excited states that can be exploited as MFE probes. For cyclic photochemical reactions under conditions of continuous illumination, the fluorescence intensity reflects the steady state concentration of ground state flavin, which in turn depends on the concentrations of long-lived radical intermediates in the photocycle. If all other species are short lived and thus present in low concentra...