title: Coupling of phytochrome B to the control of hypocotyl growth in Arabidopsis.
abstract: Etiolated seedlings of the wild-type (WT) and of the phyB-1 mutant of Arabidopsis thaliana (L.) Heynh. were exposed to red-light (R) and far-red light (FR) treatments to characterize the action of phytochrome B on hypocotyl extension growth. A single R or FR pulse had no detectable effects on hypocotyl growth. After 24-h pre-treatment with continuous FR (FRc) a single R, compared to FR pulse inhibited (more than 70%) subsequent hypocotyl growth in the WT but not in the phyB-1 mutant. This effect of FRc was fluence-rate dependent and more efficient than continuous R (Rc) or hourly FR pulses of equal total fluence. Hypocotyl growth inhibition by Rc was larger in WT than phyB-1 seedlings when chlorophyll screening was reduced either by using broad-band Rc (maximum emission 610 nm) or by using narrow-band Rc (658 nm) over short periods (24 h) or with seedlings bleached with Norflurazon. Hourly R or R+FR pulses had similar effects in WT and phyB-1 mutant etiolated seedlings. It is concluded that phytochrome B is not the only photoreceptor of Rc and that the action of phytochrome B is enhanced by a FRc high-irradiance reaction. Complementary experiments with the phyA-201 mutant indicate that this promotion of a phytochrome B-mediated response occurs via co-action with phytochrome A.
authors.affiliation: Departamento de Ecología, Facultad de Agronomía, Universidad de Buenos Aires, Argentina.
authors.forename: J J
authors.initials: JJ
authors.lastname: Casal
mesh_terms: D017360:Arabidopsis / Q000254:growth & development* / Q000528:radiation effects; D029681:Arabidopsis Proteins; D018546:Hypocotyl / Q000254:growth & development* / Q000528:radiation effects; D008027:Light; D009154:Mutation; D010786:Photoreceptor Cells; D010834:Phytochrome / Q000378:metabolism* / Q000528:radiation effects; D051942:Phytochrome A; D051939:Phytochrome B; D063245:Plant Development; D010944:Plants / Q000528:radiation effects; D013997:Time Factors; D014157:Transcription Factors
chemical_list: D029681:Arabidopsis Proteins; C497973:PHYA protein, Arabidopsis; C497952:PHYB protein, Arabidopsis; D051942:Phytochrome A; D014157:Transcription Factors; D010834:Phytochrome; D051939:Phytochrome B