Phytochrome evolution: Phytochrome genes in ferns and mosses

Abstract

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.

A phytochrome from the fern Adiantum with features of the putative photoreceptor NPH1

“…This region is conserved in all phytochromes previously isolated and therefore is a useful probe to screen for phytochrome genes and͞or cDNAs (26,27 Fig. 1 A and B).…”

The Moss Physcomitrella patens, Now and Then

“…P. patens phytochrome (Schneider-Poetsch et al, 1994) and cryptochrome genes (Imaizumi et al, 1999) have been characterized. Besides the well-known effect of increasing photon flux and directional growth responses to light (phototropism), mosses and ferns display a photopolarotropic response; in this case, tip growth localization, orientation of the plane of cell division as well as organelle movement can be modulated by the orientation of the plane of the electrical vector of linearly polarized light (Jenkins and Cove, 1983;Kadota et al, 2000).…”

Phytochrome gene diversity

“…Their N-tennini are homologous with other phytochrotnes and share 89% of their amino acids; however, the C-terminus of PhyCer is unrelated to CpPHY2 and to all other phytochromes. Additional evidence of diversity in a single taxon comprises reports of multiple phytochromes in Psilotum (Schneider-Poetsch et al 1994), and Anemia (Maucher, Scheuerlein & Schraudolf 1992). However, this diversity may result from taxon-specific diversification; in Psilotum, it may reflect a highly duplicated genome.…”