LIGHT PROMOTION OF SEED GERMINATION IN <i>Datura ferox</i> IS MEDIATED BY A HIGHLY STABLE POOL OF PHYTOCHROME

Casal, Jorge J.; Sánchez, Rodolfo A.; Benedetto, Adalberto Di; Miguel, Lucila C. de

doi:10.1111/j.1751-1097.1991.tb03930.x

Cited by 47 publications

(32 citation statements)

References 19 publications

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“…Phytochrome photoequilibria, calculated as described by Casal et al (1991), were 87 and 10%, respectively. In glasshouse experiments the R/FR ratio was measured with a Skye meter (SKR 100, remote probe SKR 110, Skye Instruments, Llandrindod Wells, Powys, UK).…”

Section: Methodsmentioning

confidence: 99%

High-irradiance responses induced by far-red light in grass seedlings of the wild type or overexpressing phytochrome A

Casal

Clough

Vierstra

1996

Planta

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Abstract. The occurrence of phytochrome-mediated highirradiance responses (HIR), previously characterised largely in dicotyledonous plants, was investigated in Triticum aestivum L., Zea mays L., Lolium muhiflorumLam. and in both wild-type Oryza sativa L. and in transgenic plants overexpressing oat phytochrome A under the control of a 35S promoter. Coleoptile growth was promoted (maize, ryegrass) or inhibited (wild-type rice) by continuous far-red light (FRc). However, at equal fluences, hourly pulses of far-red light (FRp) were equally effective, indicating that the growth responses to FRc were not true HIR. In contrast, in maize and rice, FRc increased anthocyanin content in the coleoptile in a fluence-rate dependent manner. This response was a true HIR as FRp had reduced effects. In maize, anthocyanin levels were significantly higher under FRc than under continuous red light. In rice, overexpression of phytochrome A increased the inhibition of coleoptile growth and the levels of anthocyanin under FRc but not under FRp or under continuous red light. The effect of FRc was fluence-rate dependent. In light-grown rice, overexpression of phytochrome A reduced leaf-sheath length, impaired the response to supplementary far-red light, but did not affect the response to canopy shade-light. In grasses, typical HIR, i.e. fluence-rate dependent responses showing reciprocity failure, can be induced by FRc. Under FRc, overexpressed phytochrome A operates through this action mode in transgenic rice.

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Section: Methodsmentioning

confidence: 99%

High-irradiance responses induced by far-red light in grass seedlings of the wild type or overexpressing phytochrome A

Casal

Clough

Vierstra

1996

Planta

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“…The proportion of Pfr relative to total phytochrome was calculated as described (Casal et al, 1991). Hypocotyl length was measured to the nearest 0.5 mm with a ruler in the 10 longest seedlings of each box.…”

Section: Hypocotyl Length and Cotyledon Anglementioning

confidence: 99%

GIGANTEA Regulates Phytochrome A-Mediated Photomorphogenesis Independently of Its Role in the Circadian Clock

et al. 2007

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(R.M., J.P.)GIGANTEA (GI) is a nuclear protein involved in the promotion of flowering by long days, in light input to the circadian clock, and in seedling photomorphogenesis under continuous red light but not far-red light (FR). Here, we report that in Arabidopsis (Arabidopsis thaliana) different alleles of gi have defects in the hypocotyl-growth and cotyledon-unfolding responses to hourly pulses of FR, a treatment perceived by phytochrome A (phyA). This phenotype is rescued by overexpression of GI. The verylow-fluence response of seed germination was also reduced in gi. Since the circadian clock modulates many light responses, we investigated whether these gi phenotypes were due to alterations in the circadian system or light signaling per se. In experiments where FR pulses were given to dark-incubated seeds or seedlings at different times of the day, gi showed reduced seed germination, cotyledon unfolding, and activity of a luciferase reporter fused to the promoter of a chlorophyll a/b-binding protein gene; however, rhythmic sensitivity was normal in these plants. We conclude that while GI does not affect the highirradiance responses of phyA, it does affect phyA-mediated very-low-fluence responses via mechanisms that do not obviously involve its circadian functions.

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“…For EOD or daytime light pulses the seedlings were transferred to the corresponding light cabinet and, after irradiation, were incubated in darkness in a common cabinet (25~ without exposure to green safe-light. Details of construction, fluence rates and spectra of the R/FR sources used for EOD light pulses (10-20 rain to saturate photoconversion) were as described by Casal et al (1991). Blue light (101amolphotons.…”

Section: Methodsmentioning

confidence: 99%

Is the far-red-absorbing form of Avena phytochrome A that is present at the end of the day able to sustain stem-growth inhibition during the night in transgenic tobacco and tomato seedlings?

Casal

Sánchez

Boylan

et al. 1995

Planta

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Abstract. Arena phytochrome A (phyA) overexpressed in tobacco (Nicotiana tabacum L.) and tomato (Lycopersicon sculentum Mill) was functionally characterised by comparing wild-type (WT) and transgenic seedlings. Different proportions of phytochrome in its far-red-absorbing form (Pfr/P) were provided by end-of-day (EOD) light pulses. Stem-length responses occurred largely in the range of low Pfr/P (3-61%) for WT seedlings and in the range of high Pfr/P (61-87%) for transgenic seedlings. A similar shift was observed when the photoperiod was interrupted by short light pulses providing different Pfr/P ratios and followed by 1 h dark incubation. In other experiments, Arena phyA was allowed to re-accumulate in darkness and subsequently phototransformed to Pfr but no extra inhibition of stem extension growth was observed. In transgenic tomato seedlings the response to EOD far-red light was faster and the response to a far-red light pulse delayed into darkness was larger than in the WT. Arena phyA Pfr remaining at the end of the photoperiod appears intrinsically unable to sustain growth inhibition in subsequent darkness. Arena phyA modifies the sensitivity and the kinetics of EOD responses mediated by native phytochrome.

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LIGHT PROMOTION OF SEED GERMINATION IN Datura ferox IS MEDIATED BY A HIGHLY STABLE POOL OF PHYTOCHROME

Cited by 47 publications

References 19 publications

High-irradiance responses induced by far-red light in grass seedlings of the wild type or overexpressing phytochrome A

High-irradiance responses induced by far-red light in grass seedlings of the wild type or overexpressing phytochrome A

GIGANTEA Regulates Phytochrome A-Mediated Photomorphogenesis Independently of Its Role in the Circadian Clock

Is the far-red-absorbing form of Avena phytochrome A that is present at the end of the day able to sustain stem-growth inhibition during the night in transgenic tobacco and tomato seedlings?

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