title: Flowering responses to altered expression of phytochrome in mutants and transgenic lines of Arabidopsis thaliana (L.) Heynh.
abstract: The long-day plant Arabidopsis thaliana (L.) Heynh. flowers early in response to brief end-of-day (EOD) exposures to far-red light (FR) following a fluorescent short day of 8 h. FR promotion of flowering was nullified by subsequent brief red light (R) EOD exposure, indicating phytochrome involvement. The EOD response to R or FR is a robust measure of phytochrome action. Along with their wild-type (WT) parents, mutants deficient in either phytochrome A or B responded similarly to the EOD treatments. Thus, neither phytochrome A nor B exclusively regulated flowering, although phytochrome B controlled hypocotyl elongation. Perhaps a third phytochrome species is important for the EOD responses of the mutants and/or their flowering is regulated by the amount of the FR-absorbing form of phytochrome, irrespective of the phytochrome species. Overexpression of phytochrome A or phytochrome B resulted in differing photoperiod and EOD responses among the genotypes. The day-neutral overexpressor of phytochrome A had an EOD response similar to all of the mutants and WTs, whereas R EOD exposure promoted flowering in the overexpressor of phytochrome B and FR EOD exposure inhibited this promotion. The comparisons between relative flowering times and leaf numbers at flowering of the over-expressors and their WTs were not consistent across photoperiods and light treatments, although both phytochromes A and B contributed to regulating flowering of the transgenic plants.
authors.affiliation: Commonwealth Scientific and Industrial Research Organization, Division of Plant Industry, Canberra, Australia.
authors.forename: D J
authors.initials: DJ
authors.lastname: Bagnall
authors.forename: R W
authors.initials: RW
authors.lastname: King
authors.forename: G C
authors.initials: GC
authors.lastname: Whitelam
authors.forename: M T
authors.initials: MT
authors.lastname: Boylan
authors.forename: D
authors.initials: D
authors.lastname: Wagner
authors.forename: P H
authors.initials: PH
authors.lastname: Quail
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development* / Q000528:radiation effects; D029681:Arabidopsis Proteins; D018546:Hypocotyl / Q000254:growth & development; D008027:Light; D009024:Morphogenesis / Q000235:genetics / Q000528:radiation effects; D009154:Mutation; D017440:Photoperiod; D010786:Photoreceptor Cells; D010834:Phytochrome / Q000096:biosynthesis / Q000235:genetics*; D051942:Phytochrome A; D051939:Phytochrome B; D018515:Plant Leaves / Q000254:growth & development; D030821:Plants, Genetically Modified; D012098:Reproduction / Q000235:genetics / Q000528:radiation effects; 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