Phytochrome evolution: Phytochrome genes in ferns and mosses

We have isolated phytochrome genes from the moss Physcomitrella , the fern Psilotum and PCR-generated phytochrome sequences from a few other ferns. The phytochrome gene of the moss Physcomitrella turned out not to contain the aberrant C-terminal third of the phytochrome from the moss Ceratodon , but the transmitter module-like sequences found in other phytochromes. A series of different phytochrome genes was detected in Psilotum . Differences between the amino acid sequences derived from them ranged from about 5 to more than 22%. Some of these genes are likely pseudogenes. Analysis by phylogenetic tree constructions revealed that higher and lower plant phytochromes evolved with different velocities. Lower plant phytochromes form a separate family characterized by a high degree of similarity. The amino acid differences between phytochrome types detected in a single species of higher plants are about two-fold higher than the differences between phytochromes of species of lower plants belonging to different divisions ( Physcomitrella and Selaginella ). Future studies on phytochrome sequences may eventually also throw light on the significance of Psilotum in the evolution of vascular plants.