MOLECULAR EVOLUTION OF THE PHOTOLYASE-BLUE-LIGHT PHOTORECEPTOR FAMILY

The photolyase-blue-light photoreceptor family is composed of cyclobut ane pyrimidine dimer (CPD) photolyases, (6-4) photolyases, and blue-li ght photoreceptors, CPD photolyase and (6-4) photolyase are involved i n photoreactivation for CPD and (6-4) photoproducts, respectively. CPD photolyase is classified into two subclasses, class I and II, based o n amino acid sequence similarity. Blue-light photoreceptors are essent ial light detectors for the early development of plants. The amino aci d sequence of the receptor is similar to those of the photolyases, alt hough the receptor does not show the activity of photoreactivation. To investigate the functional divergence of the family, the amino acid s equences of the proteins were aligned. The alignment suggested that th e recognition mechanisms of the cofactors and the substrate of class I CPD photolyases (class I photolyases) are different from those of cla ss II CPD photolyases (class II photolyases). We reconstructed the phy logenetic trees based on the alignment by the NJ method and the ML met hod. The phylogenetic analysis suggested that the ancestral gene of th e family had encoded CPD photolyase and that the gene duplication of t he ancestral proteins had occurred at least eight times before the div ergence between eubacteria and eukaryotes.