In plants, cryptochromes mediate phototropism, or directional growth towards a light source, in response to blue light. This response is now known to have its own set of photoreceptors, the phototropins. Unlike phytochromes and phototropins, cryptochromes are not kinases. Their flavin chromophore is reduced by light and transported into the cell nucleus, where it affects the turgor pressure and causes subsequent stem elongation. Specifically, Cry2 is responsible for blue-light mediated cotyledon and leaf expansion. Cry2 overexpression in transgenic plants increases blue light-stimulated cotyledon expansion, which results in many broad leaves and no flowers, rather than a few primary leaves with a flower. A double loss-of-function mutation in Arabidopsis thaliana Early Flowering 3 (elf3) and Cry2 genes delays flowering under continuous light was shown to accelerates it during long and short days, which suggests that Arabidopsis CRY2 may play a role in accelerating flowering time during continuous light.
Studies in animals and plants suggest that cryptochromes play a pivotal role in the generation and maintenance of circadian rhythms. In Drosophila, cryptochrome functions as a blue light photoreceptor. Exposure to blue light induces a conformation similar to that of the always active CRY mutant with a C-terminal deletion (CRY?). Cryptochrome is one of the four groups of mammalian clock genes/proteins that generate a transcription-translation negative-feedback loop (TTFL), along with Period (PER), CLOCK, and BMAL1. Cryptochromes in the photoreceptor neurons of birds' eyes are involved in magnetic orientation during migration. Cryptochromes are also essential for the light-dependent ability of Drosophila to sense magnetic fields.
http://en.wikipedia.org/wiki/Cryptochrom…