Disease relevance of CRY1

• It is demonstrated that overexpression of CRY1 resulted in hypersensitivity to blue, UV-A, and green light for the inhibition of hypocotyl elongation response [1].
• That is, CRY1 and CRY2 genes may originate from an endosymbiotic ancestor of modern-day alpha-proteobacteria, while the CRY3 gene may originate from an endosymbiotic ancestor of modern-day cyanobacteria [2].
• Here we demonstrate that substitution of two conserved tryptophans that are constituents of the flavin-reducing electron transfer chain in Escherichia coli photolyase impairs light-induced electron transfer in the Arabidopsis cryptochrome-1 photoreceptor in vitro [3].
• DNA binding was also demonstrated for the Synechocystis cryptochrome, indicating that both photoreceptors could have similar modes of action [2].
• Human cry1 expressed in baculovirus likewise shows ATP binding and autophosphorylation activity, suggesting this novel enzymatic activity may be important to the mechanism of action of both plant and animal cryptochromes [4].

High impact information on CRY1

• Humans and mice have two cryptochrome genes, CRY1 and CRY2, that are differentially expressed in the retina relative to the opsin-based visual photoreceptors [5].
• This constitutive photomorphogenic (COP) phenotype was not observed for mutants of cct1 corresponding to previously described cry1 alleles [6].
• Cryptochrome blue light photoreceptors share sequence similarity to photolyases, flavoproteins that mediate light-dependent DNA repair [6].
• For example, although most photoreceptors are known to undergo light-dependent protein modification such as phosphorylation, no blue-light dependent phosphorylation has been reported for a cryptochrome [7].
• Both yeast two-hybrid and in vitro binding studies show that there is a physical interaction between ADO1 and the photoreceptors CRY1 and phyB [8].

Biological context of CRY1

• Blue light regulates plant growth and development, and three photoreceptors, CRY1, CRY2, and NPH1, have been identified [9].
• Transgenic plants overexpressing CRY1 also exhibited a dwarf phenotype with reduced size in almost every organ [1].
• It is concluded that CRY1 is a photoreceptor mediating blue light-dependent regulation of gene expression in addition to its affect on plant growth [1].
• We conclude that cryptochrome is one of the photoreceptors mediating phototropism in plants [10].
• Photoreceptor loss-of-function mutants and dominant gain-of-function overexpression transgenes were both used to analyze the influences of the three photoreceptors, phyA, phyB, and CRY1, on the light-regulated subcellular localization of COP1 [11].

Anatomical context of CRY1

• Here we report that mutant plants lacking both the CRY1 and the CRY2 blue-light photoreceptors are deficient in the phototropic response [10].
• In Arabidopsis thaliana the participation of phytochromes A and B (phyA and phyB) in the early phase of cry1 action was investigated by determining the effects of phyA, phyB and hy1 mutations on a cry1-dependent membrane depolarization, which is caused by the activation of plasma-membrane anion channels within seconds of blue light treatment [12].
• Interaction of cryptochrome 1, phytochrome, and ion fluxes in blue-light-induced shrinking of Arabidopsis hypocotyl protoplasts [13].
• An Arabidopsis protein closely related to Synechocystis cryptochrome is targeted to organelles [2].
• Functional properties and regulatory complexity of a minimal RBCS light-responsive unit activated by phytochrome, cryptochrome, and plastid signals [14].

Associations of CRY1 with chemical compounds

• Cryptochrome 1 (CRY1) is a flavin-type blue type receptor of Arabidopsis thaliana which mediates inhibition of hypocotyl elongation [1].
• In this work we explore the relationship between cryptochrome and cytokinin signalling pathways in the promotion of photomorphogenesis [15].
• Primary root elongation in blue light may thereby involve interaction between cryptochrome and auxin signaling pathways [16].
• A blue light (cryptochrome) photoreceptor from Arabidopsis, cry1, has been identified recently and shown to mediate a number of blue light-dependent phenotypes [17].
• These data support the possibility that light-induced flavin reduction via the tryptophan chain is the primary step in the signaling pathway of plant cryptochrome [3].

Regulatory relationships of CRY1

• Our data also support an interdependency between CRY1 and the phytochromes in mediating the light-regulated subcellular localization of COP1 and thus seedling development [11].
• This result indicates that BL-activation of phototropin influences cryptochrome signaling leading to growth inhibition [18].
• Interactions within a network of phytochrome, cryptochrome and UV-B phototransduction pathways regulate chalcone synthase gene expression in Arabidopsis leaf tissue [19].

Other interactions of CRY1

• The signaling mechanism of Arabidopsis CRY1 involves direct interaction with COP1 [20].
• HY5 is a point of convergence between cryptochrome and cytokinin signalling pathways in Arabidopsis thaliana [15].
• A null mutation in PHYA impaired the membrane depolarization and prevented the early cry1-dependent phase of growth inhibition as effectively and with the same time course as mutations in CRY1 [12].
• In addition, stomata of the phot1 phot2 double mutant responded to blue light, but those of the cry1 cry2 phot1 phot2 quadruple mutant hardly responded [21].
• Therefore, cry1/cry2/phyA-mediated blue light activation of the psbD light-responsive promoter in 21-day-old Arabidopsis plants does not involve hy5, a transcription factor that mediates other phyA and blue light-induced responses [22].

Analytical, diagnostic and therapeutic context of CRY1

• Yeast two-hybrid assay, in vitro binding, in vivo chemical cross-linking, gel filtration, and coimmunoprecipitation studies indicate that CRY1 homodimerizes in a light-independent manner [23].
• Furthermore, analysis of severely phytochrome-deficient mutants showed that CRY1-mediated blue-light responses were considerably reduced, even though Western blots confirmed that levels of CRY1 photoreceptor are unaffected in these phytochrome-deficient mutant backgrounds [24].
• Stomata of the cry1 cry2 double mutant showed reduced blue light response, whereas those of the CRY1-overexpressing plants showed hypersensitive response to blue light [21].
• We investigated the full-length CRY1 protein by Fourier transform infrared (FTIR) and UV/vis difference spectroscopy [25].
• Apex dissection indicated that in phyB cry1 double mutants internode elongation anticipated the transition from the vegetative to the reproductive stage [26].

References