Phytochromes

Phytochromes consist of a protein, covalently linked to a bilin chromophore. There is two types of them which divides into A and B. They both have PAs domain and GAF domain. The difference is that phytochrome A is etiolated, displays far red and labile light. B is just red. Phytochromes interact heavily with PIFs. PIFs are a subset of transcription factors that negatively regulate photomorphogenesis. COP1 forms a complex in the nuclues, functioning as an E3 ubiquitin ligase, making positive regulators of photomorphogenesis for degradation. There are many processes in this complex for an example, cryptochromes. Haven't learned much of cryptochromes yet though.