The CRY1 Blue Light Photoreceptor of Arabidopsis Interacts with Phytochrome A In Vitro (original) (raw)
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The Plant Journal, 1997
et al., 1995a; Malhotra et al.,1995), and overexpression of USA CRY1 protein in transgenic plants conferred a blue-light hypersensitive phenotype (Lin et al.,1995b), consistent with its role as photoreceptor. Blue-light-dependent phenotypes Summary shown to be under the control of CRY1 include inhibition Blue-light responses in higher plants are mediated by of hypocotyl elongation and anthocyanin production in specific photoreceptors, which are thought to be flavoseedlings (Ahmad et al., 1995; Jackson and Jenkins, 1995; proteins; one such flavin-type blue-light receptor, CRY1 Koornneef et al., 1980). In spite of its striking homology to (for cryptochrome), which mediates inhibition of hypocotyl the DNA photolyases, CRY1 shows no demonstrable DNA elongation and anthocyanin biosynthesis, has recently binding or photoreactivating activity (Lin et al., 1995a; been characterized. Prompted by classical photobiological Malhotra et al., 1995). The structure of CRY1 suggests a studies suggesting possible co-action of the red/far-red mechanism of action involving electron transfer; the reacabsorbing photoreceptor phytochrome with blue-light tion partners and downstream transduction apparatus photoreceptors in certain plant species, the role of phytoremain to be identified. chrome in CRY1 action in Arabidopsis was investigated. A recurring theme in plant blue-light research has been The activity of the CRY1 photoreceptor can be substantially an involvement of the red/far-red-absorbing photoreceptor altered by manipulating the levels of active phytochrome phytochrome in physiological responses to blue-light treat-(Pfr) with red or far-red light pulses subsequent to bluements. Experiments in a number of monocot and dicot light treatments. Furthermore, analysis of severely phytoplant species have shown that blue-light responses such chrome-deficient mutants showed that CRY1-mediated as inhibition of hypocotyl elongation or anthocyanin accublue-light responses were considerably reduced, even mulation can be partially reversed if the blue-light pulses though Western blots confirmed that levels of CRY1 photoare followed by, or given in the presence of, saturating receptor are unaffected in these phytochrome-deficient pulses of far-red light (Casal, 1994; Gaba et al., 1984; mutant backgrounds. It was concluded that CRY1-medi-Mancinelli et al., 1991; Mohr, 1994). Such far-red reversiated inhibition of hypocotyl elongation and anthocyanin bility had been taken as evidence that phytochrome, or the production requires active phytochrome for full expresphytochrome signal transduction pathway, was somehow sion, and that this requirement can be supplied by low implicated in blue-light responses. However, interpretation levels of either phyA or phyB. of these studies has been complicated by the fact that the phytochrome photoreceptor itself directly absorbs blue light. It is therefore difficult to unequivocally distinguish
The Arabidopsis Book The Cryptochrome Blue Light Receptors
Cryptochromes are photolyase-like blue light receptors originally discovered in Arabidopsis but later found in other plants, microbes, and animals. Arabidopsis has two cryptochromes, CRY1 and CRY2, which mediate primarily blue light inhibition of hypocotyl elongation and photoperiodic control of fl oral initiation, respectively. In addition, cryptochromes also regulate over a dozen other light responses, including circadian rhythms, tropic growth, stomata opening, guard cell development, root development, bacterial and viral pathogen responses, abiotic stress responses, cell cycles, programmed cell death, apical dominance, fruit and ovule development, seed dormancy, and magnetoreception. Crypto-chromes have two domains, the N-terminal PHR (Photolyase-Homologous Region) domain that bind the chromophore FAD (fl avin adenine dinucleotide), and the CCE (CRY C-terminal Extension) domain that appears intrinsically unstruc-tured but critical to the function and regulation of cryptochromes. Most cryptochromes accumulate in the nucleus, and they undergo blue light-dependent phosphorylation or ubiquitination. It is hypothesized that photons excite electrons of the fl avin molecule, resulting in redox reaction or circular electron shuttle and conformational changes of the photoreceptors. The photoexcited cryptochrome are phosphorylated to adopt an open conformation, which interacts with signaling partner proteins to alter gene expression at both transcriptional and posttranslational levels and consequently the metabolic and developmental programs of plants.
Cryptochrome 1 Contributes to Blue-Light Sensing in Pea
Plant Physiology, 2005
Cryptochromes are widespread in higher plants but their physiological roles as blue-light photoreceptors have been examined in relatively few species. Screening in a phyA null mutant background has identified several blue-light response mutants in pea (Pisum sativum), including one that carries a substitution of a highly conserved glycine residue in the N-terminal photolyasehomologous domain of the pea CRY1 gene. Analyses of cry1, phyA, and phyB mutants show that all three photoreceptors contribute to seedling photomorphogenesis under high-irradiance blue light, whereas phyA is the main photoreceptor active under low irradiances. Triple phyA phyB cry1 mutants grown under high-irradiance blue light are indistinguishable from darkgrown wild-type plants in length and leaf expansion but show a small residual response to higher-irradiance white light. Monogenic cry1 mutants have little discernable phenotype at the seedling stage, but later in development are more elongated than wild-type plants. In addition, the loss of cry1 moderates the short-internode phenotype of older phyA mutants, suggesting an antagonism between phyA and cry1 under some conditions. Pea cry1 has a small inhibitory effect on flowering under long and short days. However, the phyA cry1 double mutant retains a clear promotion of flowering in response to blue-light photoperiod extensions, indicating a role for one or more additional blue-light photoreceptors in the control of flowering in pea.
Blue Light-Dependent in Vivo and in Vitro Phosphorylation of Arabidopsis Cryptochrome 1
THE PLANT CELL ONLINE, 2003
Arabidopsis cryptochrome 1 (cry1) is the major photoreceptor mediating blue light inhibition of hypocotyl elongation. The initial photochemistry underlying cryptochrome function and regulation remain poorly understood. We report here a study of the blue light-dependent phosphorylation of Arabidopsis cry1. Cry1 is detected primarily as unphosphorylated protein in etiolated seedlings, but it is phosphorylated in plants exposed to blue light. Cry1 phosphorylation increases in response to increased fluence of blue light, whereas the phosphorylated cry1 disappears rapidly when plants are transferred from light to dark. Light-dependent cry1 phosphorylation appears specific to blue light, because little cry1 phosphorylation is detected in seedlings treated with red light or far-red light, and it is largely independent from phytochrome actions, because no phytochrome mutants tested significantly affect cry1 phosphorylation. The Arabidopsis cry1 protein expressed and purified from insect cells is phosphorylated in vitro in a blue light-dependent manner, consistent with cry1 undergoing autophosphorylation. To determine whether cry1 phosphorylation is associated with its function or regulation, we isolated and characterized missense cry1 mutants that express full-length CRY1 apoprotein. Mutant residues are found throughout the CRY1 coding sequence, but none of these inactive cry1 mutant proteins shows blue light-induced phosphorylation. These results demonstrate that blue light-dependent cry1 phosphorylation is closely associated with the function or regulation of the photoreceptor and that the overall structure of cry1 is critical to its phosphorylation. ; fax 310-206-3987. Article, publication date, and citation information can be found at www.plantcell.org/cgi/doi/10.1105/tpc013011.
The Journal of biological chemistry, 2012
Plant photoreceptors transduce environmental light cues to downstream signaling pathways, regulating a wide array of processes during growth and development. Two major plant photoreceptors with critical roles in photomorphogenesis are phytochrome B (phyB), a red/far-red absorbing photoreceptor, and cryptochrome 1 (CRY1), a UV-A/blue photoreceptor. Despite substantial genetic evidence for cross-talk between phyB and CRY1 pathways, a direct interaction between these proteins has not been observed. Here, we report that Arabidopsis phyB interacts directly with CRY1 in a light-dependent interaction. Surprisingly, the interaction is light-dissociated; CRY1 interacts specifically with the dark/far-red (Pr) state of phyB, but not with the red light-activated (Pfr) or the chromophore unconjugated form of the enzyme. The interaction is also regulated by light activation of CRY1; phyB Pr interacts only with the unstimulated form of CRY1 but not with the photostimulated protein. Further studies...
Searching for the mechanism of signalling by plant photoreceptor cryptochrome
FEBS letters, 2015
Even though the plant photoreceptors cryptochromes were discovered more than 20 years ago, the mechanism through which they transduce light signals to their partner molecules such as COP1 (Constitutive Photomorphogenic 1) or SPA1 (Suppressor of Phytochrome A) still remains to be established. We propose that a negative charge induced by light in the vicinity of the flavin chromophore initiates cryptochrome 1 signalling. This negative charge might expel the protein-bound ATP from the binding pocket, thereby pushing off the C-terminus that covers the ATP pocket in the dark state of the protein. This conformational change should allow for phosphorylation of previously inaccessible amino acids. A partially phosphorylated 'ESSSSGRR-VPE' fragment of the C-terminus could mimic the sequence of the transcription factor HY5 that is essential for binding to the negative regulator of photomorphogenesis COP1. HY5 release through competition for the COP1 binding site could represent the lo...
The Plant Cell, 1998
A blue light (cryptochrome) photoreceptor from Arabidopsis, cry1, has been identified recently and shown to mediate a number of blue light-dependent phenotypes. Similar to phytochrome, the cryptochrome photoreceptors are encoded by a gene family of homologous members with considerable amino acid sequence similarity within the N-terminal chromophore binding domain. The two members of the Arabidopsis cryptochrome gene family (CRY1 and CRY2) overlap in function, but their proteins differ in stability: cry2 is rapidly degraded under light fluences (green, blue, and UV) that activate the photoreceptor, but cry1 is not. Here, we demonstrate by overexpression in transgenic plants of cry1 and cry2 fusion constructs that their domains are functionally interchangeable. Hybrid receptor proteins mediate functions similar to cry1 and include inhibition of hypocotyl elongation and blue light-dependent anthocyanin accumulation; differences in activity appear to be correlated with differing protein stability. Because cry2 accumulates to high levels under low-light intensities, it may have greater significance in wild-type plants under conditions when light is limited.