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1.
The red/far-red reversible phytochromes play a central role in regulating the development of plants in relation to their
light environment. Studies on the roles of different members of the phytochrome family have mainly focused on light-labile,
phytochrome A and light-stable, phytochrome B. Although these two phytochromes often regulate identical responses, they appear
to have discrete photosensory functions. Thus, phytochrome A predominantly mediates responses to prolonged far-red light,
as well as acting in a non-red/far-red-reversible manner in controlling responses to light pulses. In contrast, phytochrome
B mediates responses to prolonged red light and acts photoreversibly under light-pulse conditions. However, it has been reported
that rice (Oryza sativa L.) phytochrome A operates in a classical red/far-red reversible fashion following its expression in transgenic tobacco plants.
Thus, it was of interest to determine whether transgenic rice phytochrome A could substitute for loss of phytochrome B in
phyB mutants of Arabidopsis thaliana (L.) Heynh. We have observed that ectopic expression of rice phytochrome A can correct the reduced sensitivity of phyB hypocotyls to red light and restore their response to end-of-day far-red treatments. The latter is widely regarded as a hallmark
of phytochrome B action. However, although transgenic rice phytochrome A can correct other aspects of elongation growth in
the phyB mutant it does not restore other responses to end-of-day far-red treatments nor does it restore responses to low red:far-red
ratio. Furthermore, transgenic rice phytochrome A does not correct the early-flowering phenotype of phyB seedlings.
Received: 12 July 1998 / Accepted: 13 August 1998 相似文献
2.
The presence of a phytochrome pool down-regulated by light and the
occurrence of high-irradiance responses to far-red light are well
documented in angiosperms but not in gymnosperms. A pool of phytochrome was
identified in Pinus elliottii and
Pseudotsuga menziesii seedlings grown in darkness with
a monoclonal antibody developed against oat phytochrome A. This pool was
barely detectable in light-grown tissues. Dark-grown conifer seedlings
transferred to continuous red light showed a gradual decrease of the levels
of immunodetectable phytochrome. This decrease was significantly slower in
gymnosperms than in angiosperms. Dark-grown seedlings of P.
elliottii and P. menziesii showed enhanced
growth of the cotyledonary whorl and increased anthocyanin pigmentation of
the hypocotyl, but no hypocotyl-growth inhibition in response to continuous
far-red light. Hourly pulses were significantly less effective than
continuos far-red light. The response to far-red light was not observed in
seedlings pretreated with red light to reduce the levels of
immunodetectable phytochrome. Rudiments of phytochrome A-like function and
kinetics are present in P. elliottii and P.
menziesii. 相似文献
3.
Protonemata of Onoclea sensibilis and Diyopteris filix-mas elongate in response to both red and far-red light. The promotion caused by far-red is larger than that caused by red light. This phenomenon differs from a typical response to phytochrome, the photoreceptor pigment immediately suggested by the activity of red and far-red light. The phenomenon has been explained by two different hypotheses, one of which holds that phytochrome is solely responsible for the response, whereas the other postulates an interaction between phytochrome and P580, a yellow-green light absorbing pigment, to account for the response. The hypothesis that phytochrome is the sole photoreceptor leads to some specific predictions concerning the shapes of the dose-response curves for light-induced protonema elongation. These predictions were tested with both continuous and short-term irradiation. In all instances saturating far-red light caused greater elongation than did saturating red light, and no dose of red light duplicated the activity of saturating far-red light. Other experiments tested the interactions of red and far-red light and the effects of different doses of yellow-green light on protonema elongation. The results of many of the experiments were not in agreement with the hypothesis that phytochrome is the sole photoreceptor, whereas they were in agreement with the assumption that filament elongation is controlled by both phytochrome and P580. 相似文献
4.
Buds of Pinus sylvestris L. and Picea abies (L.) Karst. were pierced with optical fibres allowing natural light to the vicinity of apical domes. Induction of female strobiles was achieved. Since bud scales absorb more red than far-red light, the treatment may have increased the far-red light absorbing form of phytochrome.Abbreviations Pfr
far-red light absorbing form of phytochrome 相似文献
5.
Janet R. Hilton 《Planta》1982,155(6):524-528
Seeds ofBromus sterilis L. germinated between 80–100% in darkness at 15° C but were inhibited by exposure to white or red light for 8 h per day. Exposure to far-red light resulted in germination similar to, or less than, that of seeds maintained in darkness. Germination is not permanently inhibited by light as seeds attain maximal germination when transferred back to darkness. Germination can be markedly delayed by exposure to a single pulse of red light following 4 h inhibition in darkness. The effect of the red light can be reversed by a single pulse of far-red light indicating that the photoreversible pigment phytochrome is involved in the response. The response ofB. sterilis seeds to light appears to be unique; the far-red-absorbing form of phytochrome (Pfr) actually inhibiting germination.Abbreviations Pr
red absorbing form of phytochrome
- Pfr
far-red absorbing form of phytochrome 相似文献
6.
The occurrence of phytochrome-mediated highirradiance responses (HIR), previously characterised largely in dicotyledonous plants, was investigated in Triticum aestivum L., Zea mays L., Lolium multiflorum Lam. 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.Abbreviations FR
far-red light
- FRc
continuous far-red light
- FRp
pulses of far-red light
- HIR
high-irradiance responses
- LFR
low-fluence responses
- OPHYA
transgenic rice overexpressing oat phytochrome A
- Pfr
far-red light-absorbing form of phytochrome
- phyA
phytochrome A
- R
red light
- Rc
continuous red light
- VLFR
very low-fluence responses
- WT
wildtype
We thank Marcelo J. Yanovsky for his help with the photographs and Professor Rodolfo A. Sanchez for providing a reprint of the paper by P.J.A.L. de Lint. This work was supported by grants from UBA (AG041) and Fundacion Antorchas (A-13218/1-15) to J.J.C. 相似文献
7.
Light-induced changes in the photoresponses of plant stems the loss of a high irradiance response to far-red light 总被引:1,自引:1,他引:0
De-etiolation results in phytochrome destruction, greening, and the loss of the far-red high irradiance responses (HIR). Evidence is presented against the hypothesis that the loss of the far-red HIR is a direct consequence of phytochrome destruction. Loss of the far-red HIR for the inhibition of elongation in hypocotyls of Raphanus sativus involves two different, but linked, actions of phytochrome. An induction reaction requires the far-red absorbing form of phytochrome for about 20 min after which accumulation of its product depends only on time. A second reaction requires continuous light or frequent short irradiations and involves cycling of the phytochrome system. This acts on the product of the induction reaction. It is proposed that in green plants an important mode of operation of phytochrome in the light depends on pigment cycling, and that during de-etiolation this system is established under phytochrome control.Abbreviations HIR
high irradiance response
- R
red
- FR
farred light
- Ptot
phytochrome, Pr its red absorbing form, Pfr its far-red absorbing form
A.M. Jose was the holder of Ministry of Agriculture, Fisheries and Food award AE 6819 相似文献
8.
Chloroplast orientation in the green alga Mougeotia has been induced by unidirectional red or blue light, given continuously during one hour. In addition, part of the preparations obtained scattered strong far-red light simultaneously with the orienting light. This far-red light completely abolished the response to red light, consistent with phytochrome as the sensor pigment for orientation in Mougeotia. In blue light, however, the response was completely insensitive to far-red light, thus pointing to a different sensor pigment in the shortwavelength region.Abbreviation Pfr
far-red-absorbing form of phytochrome 相似文献
9.
Phytochrome Control of Longitudinal Growth and Phytochrome Synthesis in Maize Seedlings 总被引:2,自引:0,他引:2
The active, far-red light absorbing, form of phytochrome was found to inhibit growth and phytochrome levels in the mesocotyl and coleoptile of 4- to 5.5-day-old seedlings of Zea mays L. Short, low-irradiance red or far-red light treatments were used to produce different proportions of active phytochrome at the end of highdirradiance white-light periods, which left different levels of total phytochrome in the plants. After light treatments which left relatively high levels of spectrophotometrically assayable phytochrome in the seedlings, apparent phytochrome synthesis in the subsequent dark period was low regardless of the proportions of each form of the pigment present at the beginning of the dark period. In light treatments producing relatively low levels of assayable phytochrome, levels of apparent phytochrome synthesis in both red and far-red treatments and differences between apparent synthesis in red and far-red treatments were maximal. No simple correlation was found between growth and apparent phytochrome synthesis. However, growth and total phytochrome levels were positively correlated in both organs. Using a subtractive method of correlation, in which only phytochrome effects were plotted, strong linear relationships between phytochrome levels or longitudinal growth and Pfr levels were found in those light treatments leaving greater than 8% of dark control levels of phytochrome in the tissues. Using this technique non-linear, inverse relationships between Pfr and apparent phytochrome synthesis was found, indicating that modes of phytochrome control over phytochrome synthesis and growth differ. Our results are consistent with the view that in vivo assays of “bulk’ phytochrome reflect levels and states of the physiologically active phytochrome fraction under our experimental conditions in maize. 相似文献
10.
The kinetics of type 1 phytochrome were investigated in green, light-grown wheat. Phytochrome was measured by a quantitative sandwich enzyme-linked immunosorbent assay using monoclonal antibodies. The assay was capable of detecting down to 150 pg of phytochrome. In red light, rapid first-order destruction of the far-red-light-absorbing form of phytochrome (Pfr) with a half-life of 15 min was observed. Following white light terminated by red, phytochrome synthesis was delayed in darkness by about 15 h compared to plants given a terminal far-red treatment. Synthesis of the red-light-absorbing form of phytochrome (Pr) was zero-order in these experiments. Phytochrome synthesis in far-red light was approximately equal to synthesis in darkness in wheat although net destruction occurred in light-grown Avena sativa tissues in continuous far-red light, as has been reported for other monocotyledons. In wheat, destruction of Pfr apparently did not occur below a certain threshold level of Pfr or Pfr/total phytochrome. These results are consistent with an involvement of type 1 phytochrome in the photoperiodic control of flowering in wheat and other long-day plants.Abbreviations ELISA
enzyme-linked immunosorbent assay
- FR
far-red light
- HIR
high-irradiance response
- Pfr
farred-light-absorbing form of phytochrome
- Pr
red-light-absorbing form of phytochrome
- Ptot
total phytochrome (Pr + Pfr)
- R
red light
The authors wish to thank Prof. Daphne Vince-Prue (University of Reading) for many helpful discussions regarding this work. Hugh Carr-Smith was supported by a Science and Engineering Research Council studentship and Chris Plumpton by an Agricultural and Food Research Council (AFRC) studentship. B. Thomas and G. Butcher were supported by the AFRC. 相似文献
11.
The profile-to-face chloroplast movement in the green alga Mougeotia has been induced by strong blue and near-ultraviolet light pulses (6 J m-2). Simultaneously, strong red or far-red light (10 W m-2) was applied perpendicularly to the inducing beam. The response was measured photometrically. Against the far-red background the reciprocity law was found to hold for pulse durations varying two orders of magnitude. The action spectrum exhibited a maximum near 450 nm and a distinct increase in near-ultraviolet. The time-course and the spectral dependence of pulse responses of chloroplasts in Mougeotia were similar to those recorded for other plants which are sensitive only to blue. This points to an alternative sensor system active in the short-wavelength region in addition to the phytochrome system.Abbreviations FR
far-red light
- Pr
red absorbing form of phytochrome
- Pfr
far-red absorbing form of phytochrome
- R
red light
This paper is dedicated to the memory of Professor Jan Zurzycki 相似文献
12.
Chicory root explants (Cichorium intybus L. var. foliosum) of two cultivars, taken before and after hydroponic forcing, were cultured in vitro in complete darkness supplemented with red and far-red light treatments. Using 5 min red light per day, the strong stem elongation occurring in complete darkness was converted to rosette formation. This reaction was reversed to stem elongation (accompanied by leaf formation) adding 15 min far-red light after the red light. Fifteen min far-red light per day alone caused the same reaction as 5 min red/15 min far-red light. Far-red light followed by red light caused rosette formation. In stems, formed under complete darkness in vitro, the presence of phytochrome was shown. No phytochrome was detected in the root fragment itself.Abbreviations R
red light
- FR
far-red light
- GA
gibberellinic acid
- A
absorbance
- FW
fresh weight 相似文献
13.
The intracellular localisation of phytochrome in oat (Avena sativa L. cv. Garry Oat) coleoptiles was analysed by electron microscopy. Serial ultrathin sections of resin-embedded material were indirectly immunolabeled with polyclonal antibodies against phytochrome together with a gold-coupled second antibody. The limits of detectability of sequestered areas of phytochrome (SAPs) were analysed as a function of light pretreatments and amounts of the far-red absorbing form of phytochrome (Pfr) established. In 5-d-old dark-grownAvena coleoptiles SAPs were not detectable if less than 13 units of Pfr — compared with 100 units total phytochrome of 5-d-old dark-grown seedlings — were established by a red light pulse. In other sets of experiments, seedlings were preirradiated either with a non-saturating red light pulse to allow destruction to occur or with a saturating red followed by a far-red light pulse to induce first SAP formation and then its disaggregation. These preirradiations resulted in an increase of the limit of detectability of SAP formation after a second red light pulse to 38–41 and 19–23 units Pfr, respectively. We conclude that with respect to Pfr-induced SAP formation an adaptation process exists and that our data indicate that SAP formation is not a simple self-aggregation of newly formed Pfr.Abbreviations FR
far-red light
- Pfr, Pr
far-red-absorbing and red-absorbing forms of phytochrome, respectively
- Plot
total phytochrome (Pfr + Pr)
- R
red light
- SAP
sequestered areas of phytochrome
This work was supported by Deutsche Forschungsgemeinschaft (SFB 206). The competent technical assistance of Karin Fischer is gratefully acknowledged. 相似文献
14.
An amino-terminal deletion of rice phytochrome A results in a dominant negative suppression of tobacco phytochrome A activity in transgenic tobacco seedlings 总被引:19,自引:0,他引:19
Overexpression of phytochrome A results in an increased inhibition of hypocotyl elongation under red and far-red light. We used this approach to assay for the function of N-terminal mutations of rice (Oryza sativa L.) phytochrome A. Transgenic tobacco seedlings that express the wild-type rice phytochrome A (RW), a rice phytochrome A lacking the first 80 amino acids (NTD) or a rice phytochrome A with a conversion of the first 10 serines into alanine residues (S/A) were compared with untransformed wild-type tobacco (Nicotiana tabacum L. cv. Xanthi) seedlings. Experiments under different fluence rates showed that RW and, even more strongly, S/A increased the response under both red and far-red light, whereas NTD decreased the response under far-red light but hardly altered the response under red light. These results indicate that NTD not only lacks residues essential for an increased response under red light but also distorts the wild-type response under far-red light. Wild-type rice phytochrome A and, even more so, S/A mediate an enhanced phytochrome A as well as phytochrome B function, whereas NTD interferes with the function of endogenous tobacco phytochrome A as well as that of rice phytochrome A when co-expressed in a single host. Experiments with seedlings of different ages and various times of irradiation under far-red light demonstrated that the effect of NTD is dependent on the stage of development. Our results suggest that the lack of the first 80 amino acids still allows a rice phytochrome A to interact with the phytochrome transduction pathway, albeit nonproductively in tobacco seedlings.Abbreviations HIR
high-irradiance response
- NTD
N-terminal deletion mutant of rice phytochrome A
- Pfr
far-red-absorbing form of phytochrome
- Pr
red-absorbing form of phytochrome
- RW
rice wild-type phytochrome A
- S/A
serine-to-alanine mu-tant of rice phytochrome A
- wNTD
weakly expressing NTD line
- XAN
wild-type tobacco cv. Xanthi
We thank Masaki Furuya (Adv. Research Laboratory, Hitachi, Saitama, Japan) and Akira Nagatani (RIKEN Institute, Saitama, Japan) for providing the monoclonal antibodies mAP5 and mAR14. The work was supported by a grant from the Human Frontier Science Program. K.E. was a recipient of a Landesgraduiertenförderung fellowship. 相似文献
15.
Phytochrome in the far-red light absorbing form (Pfr) was observed to disappear in vivo more rapidly from the non-cation-requiring pelletable phytochrome population than from the supernantant phytochrome population of oat seedlings given an increasing dark incubation after red irradiation. The amount of pelletable phytochrome in the red light absorbing form (Pr) remained relatively stable while supernatant Pr was lost. These observations indicated that supernant Pfr was subject to loss during the incubation, while pelletable Pfr was subject to both dark reversion and loss.During the incubation, the ability of far-red irradiation to reverse the red-induced increase in phytochrome pelletability was lost, with kinetics similar to those of the loss of pelletable Pfr.Far-red reversibility of the red-induced increase in coleoptile elongation correlated with the change intotal Pfr in both supernatant and pelletable phytochrome populations, but with the change in the ratio of Pfr to total phytochrome only in the pelletable phytochrome population.The possible significance of these results is discussed with reference to the action of phytochrome in the photocontrol of physiological growth responses.Abbreviations Pfr
phytochrome in the far-red light absorbing form
- Pr
phytochrome in the red absorbing form
- Ptot
total phytochrome 相似文献
16.
In background white light, supplementary far-red (max 700 nm) is an order of magnitude less effective than supplementary far-red (max 739 nm) in the stimulation of stem extension in Sinapis alba. The relationship between phytochrome photoequilibrium and extension rate increase for the two supplementary far-red treatments is, however, very similar. This evidence indicates that phytochrome cycling is not involved in the phytochrome control of stem extension in light-grown Sinapis alba and that the response to supplementary far-red light is not fluence rate (irradiance) dependent.Abbreviations Pfr
far-red absorbing form of phytochrome
-
the phytochrome photoequilibrium (Pfr/Ptotal) 相似文献
17.
General characteristics of light sensitivity of Impatients wallerana seeds were investigated. Germination was absolutely dependent on light, irrespective of temperature. High percentages of germination were obtained by exposure to long periods of illumination or, alternatively, to several repeated short irradiations with red light. In this case, responsiveness to light was not altered by increasing either the initial incubation period in darkness or the dark intervals between short exposures. Effects of red light were reversed by far-red light, thus demonstrating the involvement of phytochrome. Evidence was presented for an interactive effect, of unknown physiological nature between red and far-red light on the germination of the seeds.Abbreviations Pr
phytochrome, red light absorbing form
- Pfr
phytochrome far-red absorbing form 相似文献
18.
Induction of flowering of etiolated Lemna paucicostata Hegelm. T-101, a short-day plant, was inhibited by far-red (FR) or blue light (BL) applied at the beginning of a 72-h inductive dark period which was followed by two short days. In either case the inhibition was reversed by a subsequent exposure of the plants to near-ultraviolet radiation (NUV), with a peak of effectiveness near 380 nm. Inhibition by BL or FR and its reversion by NUV are repeatable, i.e., NUV is acting in these photoresponses like red light although with much lower effectiveness. Thus, it is considered that NUV acts through phytochrome and no specific BL and NUV photoreceptor is involved in photocontrol of floral induction on this plant.Abbreviations BL
blue light
- FR
far-red light
- NUV
near ultraviolet radiation
- P
red-absorbing form of phytochrome
- Pfr
far-red absorbing form of phytochrome
- R
red light 相似文献
19.
A short period (15–30 min) at 30° C promotes germination of seeds of Lactuca sativa L. cv. Repolhuda in darkness. Far-red light reverses this stimulation, and the escape curves for phytochrome and high-temperature action are quite similar, indicating that the two factors act at a common point in the chain of events leading to germination. It is suggested that high temperature acts by decreasing the threshold of the active, far-red absorbing, form of phytochrome (Pfr) needed to promote germination.Abbreviations FR
far-red light
- Pfr
far-red-absorbing form of phytochrome
- R
red light 相似文献
20.
Phytochrome mediated induction of nitrate reductase activity in etiolated maize leaves 总被引:1,自引:0,他引:1
L. VIJAYA MOHAN RAO NEERAJ DATTA SUDHIR K. SOPORY SIPRA GUHA-MUKHERJEE 《Physiologia plantarum》1980,50(2):208-212
The effects of red and far-red light on the enhancement of in vitro nitrate reductase activity and on nitrate accumulation in etiolated excised maize leaves were examined. Illumination for 5 min with red light followed by a 4-h dark period caused a marked increase in nitrate reductase activity, whereas a 5-min illumination with far-red light had no effect on the enzyme activity. The effect of red light was completely reversed by a subsequent illumination with the same period of far-red light. Continuous far-red light also enhanced nitrate reductase activity. Both photoreversibility by red and far-red light and the operation of high intensity reaction under continuous far-red light indicated that the induction of nitrate reductase was mediated by phytochrome. Though nitrate accumulation was slightly enhanced by red and continuous far-red light treatments by 17% and 26% respectively, this is unlikely to account for the entire increase of nitrate reductase activity. The far-red light treatments given in water, to leaves preincubated in nitrate, enhanced nitrate reductase activity considerably over the dark control. The presence of a lag phase and inhibition of increase in enzyme activity under continuous far-red light-by tungstate and inhibitors of RNA synthesis and protein synthesis-rules out the possibility of activation of nitrate reductase and suggests de novo synthesis of the enzyme affected by phytochrome. 相似文献