10         20         30         40         50         60
         |          |          |          |          |          |
MSGSVSGCGS GGCSIVWFRR DLRVEDNPAL AAAVRAGPVI ALFVWAPEEE GHYHPGRVSR - 60
WWLKNSLAQL DSSLRSLGTC LITKRSTDSV ASLLDVVKST GASQIFFNHL YDPLSLVRDH - 120
RAKDVLTAQG IAVRSFNADL LYEPWEVTDE LGRPFSMFAA FWERCLSMPY DPESPLLPPK - 180
KIISGDVSKC VADPLVFEDD SEKGSNALLA RAWSPGWSNG DKALTTFING PLLEYSKNRR - 240
KADSATTSFL SPHLHFGEVS VRKVFHLVRI KQVAWANEGN EAGEESVNLF LKSIGLREYS - 300
RYISFNHPYS HERPLLGHLK FFPWAVDENY FKAWRQGRTG YPLVDAGMRE LWATGWLHDR - 360
IRVVVSSFFV KVLQLPWRWG MKYFWDTLLD ADLESDALGW QYITGTLPDS REFDRIDNPQ - 420
FEGYKFDPNG EYVRRWLPEL SRLPTDWIHH PWNAPESVLQ AAGIELGSNY PLPIVGLDEA - 480
KARLHEALSQ MWQLEAASRA AIENGSEEGL GDSAEVEEAP IEFPRDITME ETEPTRLNPN - 540
RRYEDQMVPS ITSSLIRPEE DEESSLNLRN SVGDSRAEVP RNMVNTNQAQ QRRAEPASNQ - 600
VTAMIPEFNI RIVAESTEDS TAESSSSGRR ERSGGIVPEW SPGYSEQFPS EENRIGGGST - 660
TSSYLQNHHE ILNWRRLSQT G

Blue light has played a particularly important role as a driving force in evolution since it is the only component of the sunlight spectrum to penetrate to significant depths in aquatic environments, such as those in which life began on earth. Five classes of blue-light photoreceptors have been identified in bacteria, fungi, plants, and animals. These include the BLUF-domain proteins (AppA, PAC), PAS-domain proteins (PYP, wc-1), phototropins, UV/blue opsins, and photolyase/cryptochrome family. Of these blue-light photoreceptors, only the latter is shared by all of these diverse organisms. Cryptochromes were initially identified as putative photoreceptors because of their high degree of homology to the blue-light-activated DNA repair enzyme photolyase and the observation that, like photolyase, they contain two chromophores, a photoantenna pigment, folate, and the catalytic chromophore FAD. Photolyases catalyze the lightdependent repair of UV-induced cyclobutane pyrimidine dimers or pyrimidine-pyrimidone photoproducts in DNA, whereas cryptochromes lack DNA repair activity and act as photoreceptors for a variety of growth and adaptive responses, such as circadian rhythms and light-dependent transcriptional regulation. The photocycle of photolyase is well characterized. Photolyase binds UV-damaged DNA independently of light; absorption of a photon by the photoantenna MTHF is followed by resonance energy transfer to the catalytic chromophore FADH-, which splits the photoproduct by nonreductive electron transfer. Mediates blue light-induced gene expression through the inhibition of COP1-mediated degradation of the transcription factor BIT1. Involved in blue light-dependent stomatal opening, CHS gene expression, inhibition of stem growth and increase of root growth.