A light-regulated pool of phytochrome and rudimentary high-irradiance responses under far-red light in Pinus elliottii and Pseudotsuga menziesii

Abstract

In angiosperms, each subunit of these dimeric cytoplasmic photoreceptors consists of an apoprotein of 120‐130 kDa The presence of a phytochrome pool down-regulated and a covalently attached linear tetrapyrrol chromophore by light and the occurrence of high-irradiance (Quail et al., 1995). Phytochromes possess two photoresponses to far-red light are well documented in interconvertible forms: the R-absorbing form (Pr) and angiosperms but not in gymnosperms. A pool of the FR-absorbing form (Pfr). In Arabidopsis thaliana the phytochrome was identified in Pinus elliottii and phytochrome apoprotein gene family includes five memPseudotsuga menziesii seedlings grown in darkness bers, denoted PHYA through PHYE (Clack et al., 1994). with a monoclonal antibody developed against oat Five phytochrome genes, PHYA, PHYB1, PHYB2, phytochrome A. This pool was barely detectable in PHYE, and PHYF, are present in tomato (Pratt et al., light-grown tissues. Dark-grown conifer seedlings 1997). Phytochrome genes found in flowering plants transferred to continuous red light showed a gradual belong to one of the three most divergent lineages, PHYA, decrease of the levels of immunodetectable phytoPHYB/D/E and PHYC/F. identified by the presence or chrome. This decrease was significantly slower in gymabsence of specific introns in the analysis of full-length nosperms than in angiosperms. Dark-grown seedlings