Cryptochrome expression

WADE, H.K., BIBIKOVA, T.N., VALENTINE, W.J., JENKINS, G.I., Interactions within a network of phytochrome, cryptochrome and UV-B phototransduction pathways regulate chalcone synthase gene expression in Arabidopsis leaf tissue, Plant J., 2001, 25, 675-685. 

Kay That was a good experiment that Margaret Ahmad did. She over-expressed cryptochrome and then used levels of light that are much lower and which don t initiate a response in the wild-type but do in the over-expressor. This is how she was able to determine a CRYl-specific action spectrum. 

Foster Tony Cashmore has consistently argued that we simply can t know what the absorption spectra of the cryptochromes will be. Others have argued differently. The empirical evidence of a comparison between a flavin absorption spectrum and that of the new CRYl over-expression by Ahmad and colleagues suggests that there is a close correlation. 

Ketinal-degenerate mice lacking cryptochromes show markedly decreasedphotic sensitivity for behaviour and photic induction of SCNgene expression... 

Sargent ML, Briggs WR, Woodward DO 1966 Circadian nature of a rhythm expressed by an invertaseless strain of Neurospora crassa. Plant Physiol 41 1343—1349 Selby CP, Thompson C, Schmitz TM, Van Gelder RN, Sancar A 2000 Functional redundancy of cryptochromes and classical photoreceptors for nonvisual ocular photoreception in mice. Proc Natl Acad Sci USA 97 14697-14702... 

Somers DE, Devlin PF, Kay SA 1998 Phytochromes and cryptochromes in the entrainment of th Arabidopsis circadian clock. Science 282 1488-1490 Stanewsky R, Kaneko M, Emery P et al 1998 The cryb mutation identifies cryptochrome as a circadian photoreceptor in Drosophila. Cell 95 681-692 Wang ZY, Tobin EM 1998 Constitutive expression of the CIRCADIAN CLOCK ASSOCIATED 1 CCAl gene disrupts circadian rhythms and suppresses its own expression. Cell 93 1207-1217... 

Kay It is external coincidence. Both are required. If you activate phytochrome A (phjA) and cryptochrome 2 cry 2) in wild-type plants at the end of the day in short days this has no effect on flowering because the phase of CO expression is such that it is at too low a level. It really seems to be entrainment regulating CO waveform. This is where Bunning in the 1940s was brilliant in proposing how this could work. This story will get even prettier when we fulfil the prediction that this light is leading to some post-translational modulation of CO protein or potentially a CO partner. 

Egan ES, Franklin TM, Hilderbrand-Chae MJ et al 1999 An extraretinally expressed insect cryptochrome with similarity to the blue light photoreceptors of mammals and plants. J Neurosci 19 3665-3673... 

Most cryptochromes contain 20-200-amino acid G-terminal extensions beyond the photolyase homology region. Interestingly, it has been found that expression of this G-terminal domain of Arabidopsis cryptochromes confers a constitutive light-on phenotype (Yang et al, 2001). Thus, it appears that the G terminus acts as the effector function that is somewhat repressed by the photolyase-like region in the dark and relieved in the light. 

T6th, R., Kevei, E., Hall, A., Millar, A.J., Nagy.E, and Kozma-Bogndr, L., Circadian clock-regulated expression of phytochrome and cryptochrome genes in Arabidopsis, Plant Physiol, 127,1607,2001. 

Lin, C. et al.. Expression of an Arabidopsis cryptochrome gene in transgenic tobacco results in hypersensitivity to blue, UV-A, and green light, Proc. Natl Acad. Scl USA, 92, 8423, 1995. 

Guo, H. et al.. Regulation of flowering time hy Arabidopsis photoreceptors. Science, 279,1360,1998. Imaizumi, X, Kanegae, X, and Wada, M., Cryptochrome nucleocytoplasmatic distribution and gene expression are regulated by light quality in the fern Adiantum capillus-veneris. Plant Cell, 12, 81, 2000. 

Surprisingly, cryptochrome was not found solely in the retina. In addition to low levels found in all tissues, Cryl was also expressed in the SCN, and Cryl mRNA oscillated with circadian rhythmicity, which indicated an additional role for cryptochrome in circadian clock function. Based on the mRNA expression pattern, we postulated a role for Cry2 in circadian photoreception in the retina as well as a hght-independent role for Cryl in the circadian clock mechanism in the SCN. 

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