A role of phytochrome in photoperiodic induction: Two‐phytochrome‐pool theory

Takimoto, Atsushi; Saji, Hikaru

doi:10.1111/j.1399-3054.1984.tb05190.x

Cited by 34 publications

(19 citation statements)

References 86 publications

(69 reference statements)

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“…In SDP physiological experiments have suggested that two phytochrome pools might play roles in regulating flowering time (Saji et al, 1982;Takimoto and Saji, 1984). The results of our flowering time experiments suggest that this is also true in Arubidopsis, a LDP.…”

Section: Dlscusslonsupporting

confidence: 66%

Phytochrome A and Phytochrome B Have Overlapping but Distinct Functions in Arabidopsis Development

et al. 1994

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Plant responses to red and far-red light are mediated by a family of photoreceptors called phytochromes. In Arabidopsis thaliana, there are genes encoding at least five phytochromes, and it is of interest to learn if the different phytochromes have overlapping or distinct functions. To address this question for two of the phytochromes in Arabidopsis, we have compared light responses of the wild type with those of a phyA null mutant, a phyB null mutant, and a phyA phyB double mutant. We have found that both phyA and phyB mutants have a deficiency in germination, the phyA mutant in far-red light and the phyB mutant in the dark. Furthermore, the germination defect caused by the phyA mutation in farred light could be suppressed by a phyB mutation, suggesting that phytochrome B (PHYB) can have an inhibitory as well as a stimulatory effect on germination. In red light, the phyA phyB double mutant, but neither single mutant, had poorly developed cotyledons, as well as reduced red-light induction of CAB gene expression and potentiation of chlorophyll induction. The phyA mutant was deficient in sensing a flowering response indudive photoperiod, suggesting that PHYA participates in sensing daylength. In contrast, the phyB mutant flowered earlier than the wild type (and the phyA mutant) under all photoperiods tested, but responded to an inductive photoperiod. Thus, PHYA and PHYB appear to have complementary fundions in controlling germination, seedling development, and flowering. We discuss the implications of these results for possible mechanisms of PHYA and PHYB signal transduction.

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Section: Dlscusslonsupporting

confidence: 66%

Phytochrome A and Phytochrome B Have Overlapping but Distinct Functions in Arabidopsis Development

et al. 1994

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“…Pfr of type II phytochrome, including PhyB and probably other phytochromes, is stable in the dark for long periods, for years in dry seeds, and then induces responses. In contrast, Pfr of Type I phytochrome, which corresponds to PhyA, is unstable and disappears rapidly after irradiation with R light in the subsequent dark period (Takimoto and Saji, 1984). However, the time course of disappearance of the effectiveness of each FR light pulse in the present study (Fig.…”

Section: Phya Signal For Hir Is Short-livedcontrasting

confidence: 49%

Elementary Processes of Photoperception by Phytochrome A for High-Irradiance Response of Hypocotyl Elongation in Arabidopsis,

2000

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“…Several phytochrome actions are known to be involved in photoperiod sensing, and these separate actions may be mediated by phytochromes other than PhyB (Takimoto and Saji, 1984;Halliday et al, 1994;Johnson et al, 1994). PHYA and PHYC may also be involved in photoperiod sensitivity.…”

Section: Discussionmentioning

confidence: 99%

The Sorghum Photoperiod Sensitivity Gene, Ma3, Encodes a Phytochrome B

et al. 1997

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The Ma, gene is one of six genes that regulate the photoperiodic sensitivity of flowering in sorghum (Sorghum bicolor [L.] Moench).The masR mutation of this gene causes a phenotype that is similar to plants that are known to lack phytochrome B, and masR sorghum lacks a 123-kD phytochrome that predominates in light-grown plants and that is present in non-magR plants. A population segregating for Ma, and masR was created and used to identify two randomly amplified polymorphic DNA markers linked to Ma,. These two markers were cloned and mapped in a recombinant inbred population as restriction fragment length polymorphisms. cDNA clones of PHYA and PHYC were cloned and sequenced from a cDNA library prepared from green sorghum leaves. Using a genome-walking technique, a 7941 -bp partia1 sequence of PHYB was determined from genomic DNA from masR sorghum. PHYA, PHYB, and P H Y C all mapped to the same linkage group. The Ma,-linked markers mapped with PHYB more than 121 centimorgans from PHYA and PHYC. A frameshift mutation resulting in a premature stop codon was found in the PHYB sequence from magR sorghum. Therefore, we conclude that the Ma, locus in sorghum is a PHYB gene that encodes a 123-kD phytochrome.The transition from vegetative to reproductive growth is the result of the activation of genes responsible for inflorescence and floral organ formation. These genes, which control apex identity and floral organ morphogenesis, are strictly regulated, since their improper expression results in abnormal flowers and inflorescences (Okamuro et al., 1993;Veit et al., 1993). The initial activation of these genes is usually the result of environmental cues that indicate an appropriate time to flower. The mechanisms by which environmental factors activate inflorescence and floral organ production are complex and many genes are known to be involved in the transduction of environmental signals that regulate flowering (Bernier et al., 1993; Coupland, 1995).Of all of the environmental factors that are sensed by plants, daylength is probably the most important in inducing flowering. The phenomenon whereby daylength regulates flowering is referred to as photoperiodism. An understanding of the effect of daylength on reproductive development has agronomic importance because the ability to alter flowering time allows the cultivation of a species in environments that differ greatly from the one in which it originally evolved. Our understanding of photoperiodism has historically relied upon a physiological examination of the phenomenon. Recently, genetic analysis of floral induction has provided new insights into this process. In the LD plant Arabidopsis thaliana a series of genes has been recognized that influences flowering time, and these genes have been categorized into six phenotypic groups based on earliness or lateness in flowering in response to short days, long days, and vernalization; (Coupland, 1995). The existence of these separate phenotypic classes suggests the existence of severa1 pathways that regulate photoperiod sens...

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A role of phytochrome in photoperiodic induction: Two‐phytochrome‐pool theory

Cited by 34 publications

References 86 publications

Phytochrome A and Phytochrome B Have Overlapping but Distinct Functions in Arabidopsis Development

Phytochrome A and Phytochrome B Have Overlapping but Distinct Functions in Arabidopsis Development

Elementary Processes of Photoperception by Phytochrome A for High-Irradiance Response of Hypocotyl Elongation in Arabidopsis,

The Sorghum Photoperiod Sensitivity Gene, Ma3, Encodes a Phytochrome B

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