The phytochrome apoprotein family inArabidopsis is encoded by five genes: the sequences and expression ofPHYD andPHYE

Abstract

Two novel Arabidopsis phytochrome genes, PHYD and PHYE, are described and evidence is presented that, together with the previously described PHYA, PHYB and PHYC genes, the primary structures of the complete phytochrome family of this plant are now known. The PHYD- and PHYE-encoded proteins are of similar size to the other phytochrome apoproteins and show sequence similarity along their entire lengths. Hence, red/far-red light sensing in higher plants is mediated by a diverse but structurally conserved group of soluble photoreceptors. The proteins encoded by the PHYD and PHYE genes are more closely related to phytochrome B than to phytochromes A or C, indicating that the evolution of the PHY gene family in Arabidopsis includes an expansion of a PHYB-related subgroup. The PHYB and PHYD phytochromes show greater than 80% amino acid sequence identity but the phenotypes of phyB null mutants demonstrate that these receptor forms are not functionally redundant. The five PHY mRNAs are, in general, expressed constitutively under varying light conditions, in different plant organs, and over the life cycle of the plant. These observations provide the first description of the structure and expression of a complete phytochrome family in a higher plant.

Photo and hormonal control of meristem identity in the Arabidopsis flower mutants apetala2 and apetala1.

“…To explore this hypothesis, we used a genetic approach to test whether phytochrome activity is required for SD axillary flower formation. There are at least five phytochrome genes in Arabidopsis (PHYA to PHYE; Sharrock and Quail, 1989;Clack et al, 1994). The activities of all five genes are strongly suppressed by the hy7 mutation that blocks phytochrome chromophore biosynthesis (Parks and Quail, 1991).…”

Light-Induced Nuclear Translocation of Endogenous Pea Phytochrome A Visualized by Immunocytochemical Procedures

“…Phytochromes are soluble chromoproteins that convert photoreversibly between two spectrally distinct forms when sequentially absorbing red (R) and far-red (FR) light, and this interconversion occurs immediately both in vivo and in vitro (Butler et al, 1959). Phytochromes are encoded by a small gene family (phytochrome genes PHYA to PHYE in Arabidopsis; Sharrock and Quail, 1989;Clack et al, 1994). Studies with mutants deficient in specific phytochromes have shown that phytochrome A (PhyA) and phytochrome B (PhyB) have distinct action spectra for the photoinduction of seed germination (Shinomura et al, 1996) and distinct fluence and wavelength requirements for expression of the chlorophyll a / b binding protein gene ( CAB ) (Hamazato et al, 1997).…”

Lysine 206 inArabidopsisphytochrome A is the major site for ubiquitin-dependent protein degradation

“…Active Pfr form can be converted back to the inactive Pr form by absorption of specific far-red light (9,10). The model plant, Arabidopsis thaliana, contains five genes (PHYA to PHYE) that encode phytochrome apoproteins (11,12). Phytochromes are classified as light labile phytochrome A (phyA) and light stable phytochromes B E (phyB-phyE) (13).…”