COMPARATIVE PHOTOCHEMICAL ANALYSIS OF HIGHLY PURIFIED 124 KILODALTON OAT and RYE PHYTOCHROMES <i>in vitro</i>

Lagarias, J. Clark; Kelly, John M.; Cyr, Karen L.; Smith, William O.

doi:10.1111/j.1751-1097.1987.tb04729.x

Cited by 126 publications

(94 citation statements)

References 21 publications

(21 reference statements)

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“…When the vertical axis of PhyA action spectrum in Fig. SA is re-plotted on linear scale, the resultant spectrum fits quite well with the absorption spectrum of purified PhyA in the Pr form (35)(36)(37). This evidence indicates that the absorption of light by PhyA in the Pr form is the primary action of the response.…”

Section: Discussionsupporting

confidence: 52%

“…The photon fluence required for 50% induction of the PhyA reaction (Fig. 4A) was estimated to convert only 0.01% of Pr to Pfr if calculated on the basis of the extinction coefficient and quantum yield of purified oat PhyA (36,37). Thus, quite a small amount of Pfr appears to be sufficient to trigger the PhyA-dependent germination ofArabidopsis seeds.…”

Section: Discussionmentioning

confidence: 99%

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Action spectra for phytochrome A- and B-specific photoinduction of seed germination in Arabidopsis thaliana.

Shinomura

Nagatani²,

Hanzawa³

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

499

501

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We have examined the seed germination in Arabidopsis thaliana of wild type (wt), and phytochrome A (PhyA)-and B (PhyB)-mutants in terms of incubation time and environmental light effects. Seed germination of the wt and PhyA-null mutant (phyA) was photoreversibly regulated by red and far-red lights of 10-1,000 ,umol m-2 when incubated in darkness for 1-14 hr, but no germination occurred in PhyB-null mutant (phyB). When wt seeds and thephyB mutant seeds were incubated in darkness for 48 hr, they synthesized PhyA during dark incubation and germinated upon exposure to red light of 1-100 nmol m-2 and far-red light of 0.5-10 ,umol m-2, whereas the phyA mutant showed no such response. The results indicate that the seed germination is regulated by PhyA and PhyB but not by other phytochromes, and the effects of PhyA and PhyB are separable in this assay. We determined action spectra separately for PhyA-and PhyB-specific induction of seed germination at Okazaki large spectrograph. Action spectra for the PhyA response show that monochromatic 300-780 nm lights of very low fluence induced the germination, and this induction was not photoreversible in the range examined. Action spectra for the PhyB response show that germination was photoreversibly regulated by alternate irradiations with light of 0.01-1 mmol m-2 at wavelengths of 540-690 nm and 695-780 nm. The present work clearly demonstrated that PhyA photoirreversibly triggers the germination upon irradiations with ultraviolet, visible and farred light of very low fluence, while PhyB controls the photoreversible effects of low fluence.

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Section: Discussionsupporting

confidence: 52%

Section: Discussionmentioning

confidence: 99%

Action spectra for phytochrome A- and B-specific photoinduction of seed germination in Arabidopsis thaliana.

Shinomura

Nagatani²,

Hanzawa³

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

499

501

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“…In the equations, N i is the fluence rate at a specific wavelength, and both Ri and FRi from measurements of phytochromes purified from dark-grown oat and rye seedlings were used (1,21,22). The k d of phyB PfrPr to PrPr was calculated from t 1/2 of yeast expressed phyB (23,24).…”

Section: Methodsmentioning

confidence: 99%

Characterization of the requirements for localization of phytochrome B to nuclear bodies

Meng

Schwab

Chory

2003

Proc. Natl. Acad. Sci. U.S.A.

158

213

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Phytochromes are red-and far-red-sensing photoreceptors that detect the quantity, quality, and duration of light throughout the entire life cycle of plants. Phytochromes accumulate in the cytoplasm in the dark. As one of the earliest responses after light illumination, phytochromes localize to the nucleus where they become associated with discrete nuclear bodies (NBs). Here, we describe the steady-state dynamics of Arabidopsis phytochrome B (phyB) localization in response to different light conditions and define four phyB subnuclear localization patterns: diffuse nuclear localization, small and numerous NBs only, both small and large NBs, and large NBs only. We show that phyB nuclear import is not sufficient for phyB NB formation. Rather, phyB accumulation in NBs is mainly determined by the percentage of the total amount of phyB protein that is in the active phyB conformer, with large NBs always correlating with strong phyB responses. A genetic screen to identify determinants required for subnuclear localization of phyB resulted in several phyB mutants, mutants deficient in phytochrome chromophore biosynthesis, and mutations in at least one previously uninvestigated locus. This study lays the groundwork for future investigations to identify the molecular mechanisms of light-regulated partitioning of plant photoreceptors to discrete subnuclear domains.

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“…Thus, it is the broad band associated with the electronic transitions, in both Pr and Pfr, that accounts for most absorption in vitro. We underline this point as it will be demonstrated below that, with respect to 11 Both measured spectra and the resulting fits are shown.…”

Section: Resultsmentioning

confidence: 85%

“…The phytochrome absorption spectra were taken from the published data of Lagarias et al 11 Spectral decomposition of the Q y absorption region was performed with a minimum number of asymmetric Gaussian sub-bands (four) in order to approximately quantitate the electronic/vibrational band contributions. The software used an Excel solver to perform the minimisation.…”

Section: Methodsmentioning

confidence: 99%

On phytochrome absorption and the phytochrome photoequilibrium in a green leaf: environmental sensitivity and photoequilibrium time

Rivadossi

Garlaschi

Casazza

et al. 2008

Photochem Photobiol Sci

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The average, corrected attenuance spectra for both spectral forms of phytochrome in a mature leaf were calculated. Optical masking by chlorophyll together with the detour effect (optical path lengthening effect) due to multiple light scattering led to large changes in both the Q y band shape and wavelength position and the effective intensity of the weak vibrational bands increases. The Pfr/Pr oscillator-strength-ratio between 400-750 nm (0.93 in vitro), becomes 1.63 in a leaf. Thus the dominant absorption form is Pfr. These two values permit calculation of the phytochrome photoequilibrium under conditions of "daylight" illumination both in vitro and in folia. These values are 0.6 and 0.38 respectively. Previous literature estimates for the situation in vitro, based on the 660/730 nm absorption ratio, yielded values close to 0.6. It is demonstrated that this large decrease in the phytochrome photoequilibrium in a leaf has the effect of translating this parameter to a position on the dose (red/far-red light ratio)-response (Pfr/Ptot) plot towards greater sensitivity to changes in the environmental red/far-red ratio. The increased sensitivity factor is almost five-fold for the "daylight" environment and is even greater for the various "shade-light" environments. The approximate time taken to attain photoequilibrium (1/e lifetime) has also been calculated for phytochrome in a leaf in different light environments. For the "daylight" environment the photoequilibration time is ∼5 s, which increases into the 20-80 s interval under different degrees of "shade light". Thus, despite the strong optical masking by chlorophyll in a mature leaf, the phytochrome photoequilibrium is attained quite rapidly on a physiological time scale.

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COMPARATIVE PHOTOCHEMICAL ANALYSIS OF HIGHLY PURIFIED 124 KILODALTON OAT and RYE PHYTOCHROMES in vitro

Cited by 126 publications

References 21 publications

Action spectra for phytochrome A- and B-specific photoinduction of seed germination in Arabidopsis thaliana.

Action spectra for phytochrome A- and B-specific photoinduction of seed germination in Arabidopsis thaliana.

Characterization of the requirements for localization of phytochrome B to nuclear bodies

On phytochrome absorption and the phytochrome photoequilibrium in a green leaf: environmental sensitivity and photoequilibrium time

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