Malformations in maxillary incisors: case report of radicular palatal groove

This report describes malformations of anterior teeth and a case of a palatal radicular groove in an upper lateral incisor with periodontal complications. The patient was first diagnosed with an endodontic problem. Endodontic treatment alone failed to resolve the pain. Therefore, after the palatal groove had been properly diagnosed, a palatal flap procedure was carried out including removal of the granulation tissue and careful scaling and root planing of the area with the groove. No odontoplasty was done. Endodontic therapy of the tooth was completed and periapical healing was evident. The treatment effectively reduced the gingival probing depth and led to an asymptomatic tooth.

Effect of transcutaneous electrical nerve stimulation on pain perception threshold of human teeth: a double-blind, placebo-controlled study

In this double-blind, placebo-controlled study, we studied the effect of three different transcutaneous electrical nerve stimulation (TENS) devices with extra- and intraoral electrodes on the pain perception thresholds of 234 unrestored, caries-free human teeth of 66 healthy individuals subjected to stimulation with an electric pulp tester. A placebo control collective of 64 healthy subjects received no electrical stimulation, since an inactive TENS device was used. In all tooth types tested (maxillary and mandibular incisors and premolars), the use of the active TENS devices resulted in an increase of 16.3-32.5% versus baseline in the pain perception threshold. The differences between active TENS and baseline were statistically significant for both TENS devices using extraoral electrodes (P < 0.05). No statistically significant differences were found between the different devices tested (P > 0.05). In the placebo collective, the increase in the pain perception threshold ranged between 6.4% and 10.3% versus baseline. There were no significant differences between placebo TENS and baseline on the one hand and between placebo TENS and the active TENS devices on the other hand (P > 0.05). The findings suggest that, as an alternative to local anesthetics, TENS seems not to be useful in the case of painful dental interventions, since it offered only minor advantages over a placebo.

A new type of mutation in the plant photoreceptor phytochrome B causes loss of photoreversibility and an extremely enhanced light sensitivity

Photoreversibility, reversion of the inductive effect of a brief red light pulse by a subsequent far-red light pulse, is a property of photoresponses regulated by the plant photoreceptor phytochrome B (phyB). We screened for mutants with impaired photoreversibility to gain better insight into the phyB-specific signalling cascade. The phenotype of the mutant described is caused by a single amino acid exchange in a phyB subdomain that is highly conserved in all phytochromes but whose functional significance was unknown. The mutated phyB showed a slower dark reversion but no major alterations in its spectral properties. In addition to its loss of photoreversibility, the mutant also exhibited a hypersensitivity towards continuous red-light irradiation and an altered phenotype of adult plants under short-day conditions.

Photocontrol of subcellular partitioning of phytochrome-B:GFP fusion protein in tobacco seedlings

Photomorphogenesis of higher plants is regulated by photoreceptors including the red/far-red light-absorbing phytochromes, blue-UV/A sensing cryptochromes and as yet uncharacterized UV/B receptors. Specific phototransduction pathways that are controlled by either individual or interacting photoreceptors mediate regulation. Phytochrome B (phyB) is the major red light-sensing photoreceptor. Phototransduction mediated by this light sensor has been shown to include light-dependent nuclear import and interaction of phyB with transcription factor-like proteins in the nucleus. Here we report that nuclear import of phyB and physiological responses regulated by this photoreceptor exhibit very similar wavelength- and fluence rate-dependence. Nuclear import of phyB is insensitive to single red, blue and far-red light pulses. It is induced by continuous red light and to a lesser extent by continuous blue light, whereas far-red light is completely ineffective. The data presented indicate that light-dependent partitioning of phyB exhibits features characteristic of blue light responsiveness amplification, a phenomenon that is thought to be mediated by interaction of phyB with CRY1.

eid1: a new Arabidopsis mutant hypersensitive in phytochrome A-dependent high-irradiance responses

To identify specific mutants for components of phytochrome A (phyA) signaling in Arabidopsis, we established a light program consisting of multiple treatments with alternating red and far-red light. In wild-type seedlings, irradiation with multiple red light pulses can reduce the amount of phyA, which in turn decreases the high-irradiance responses (HIRs) mediated by the subsequent treatments with far-red light. Our mutants were able to avoid this red light-dependent reduction of the HIR. Here, we describe eid1, a new recessive mutant with increased sensitivity to far-red light. The eid1 mutation maps to the top of chromosome 4. The mutants showed no change in phenotype in darkness or under continuous white light, but they exhibited an increased sensitivity to red light and an increased persistence of HIR during prolonged dark phases after multiple short pulses of far-red light. The eid1 seedlings accumulated normal amounts of phytochrome and showed no alterations in the degradation or de novo synthesis of phyA. The expression of the Eid1 phenotype requires the presence of phyA. Our data provide evidence that EID1 is a negatively acting component in the phyA-dependent HIR-signaling pathway.

Light-induced nuclear import of phytochrome-A:GFP fusion proteins is differentially regulated in transgenic tobacco and Arabidopsis

Phytochromes (phy) are a family of photoreceptors that control various aspects of light-dependent plant development. Phytochrome A (phyA) is responsible for the very low fluence response (VLFR) under inductive light conditions and for the high irradiance response (HIR) under continuous far-red light. We have recently shown that nuclear import of rice phyA:GFP is regulated by VLFR in transgenic tobacco. The import is preceded by very fast, light-induced formation of sequestered areas of phyA:GFP in the cytosol. Here we report that expression of the Arabidopsis phyA:GFP fusion protein in phyA-deficient Arabidopsis plants complements the mutant phenotype. In these transgenic Arabidopsis lines, both light-dependent cytosolic formation of sequestered areas of the phyA:GFP as well as VLFR or HIR-mediated nuclear import of the fusion protein was observed. By contrast, light-dependent nuclear import of the same fusion protein was induced only by continuous far-red light (HIR) but not by pulses of far-red light (VLFR) in transgenic tobacco. These results demonstrate that photoregulation of intracellular partitioning of the Arabidopsis phyA:GFP differs significantly in different genetic backgrounds.

Arabidopsis phytochromes C and E have different spectral characteristics from those of phytochromes A and B

The red/far-red light absorbing phytochromes play a major role as sensor proteins in photomorphogenesis of plants. In Arabidopsis the phytochromes belong to a small gene family of five members, phytochrome A (phyA) to E (phyE). Knowledge of the dynamic properties of the phytochrome molecules is the basis of phytochrome signal transduction research. Beside photoconversion and destruction, dark reversion is a molecular property of some phytochromes. A possible role of dark reversion is the termination of signal transduction. Since Arabidopsis is a model plant for biological and genetic research, we focussed on spectroscopic characterization of Arabidopsis phytochromes, expressed in yeast. For the first time, we were able to determine the relative absorption maxima and minima for a phytochrome C (phyC) as 661/725 nm and for a phyE as 670/724 nm. The spectral characteristics of phyC and E are strictly different from those of phyA and B. Furthermore, we show that both phyC and phyE apoprotein chromophore adducts undergo a strong dark reversion. Difference spectra, monitored with phycocyanobilin and phytochromobilin as the apoprotein's chromophore, and in vivo dark reversion of the Arabidopsis phytochrome apoprotein phycocyanobilin adducts are discussed with respect to their physiological function.

Phosphorylation of the parsley bZIP transcription factor CPRF2 is regulated by light

The analysis of the complex network of signal transduction chains has demonstrated the importance of transcription factor activities for the control of gene expression. To understand how transcription factor activities in plants are regulated in response to light, we analyzed the common plant regulatory factor 2 (CPRF2) from parsley (Petroselinum crispum L.) that interacts with promoter elements of light-regulated genes. Here, we demonstrate that CPRF2 is a phosphoprotein in vivo and that its phosphorylation state is rapidly increased in response to light. Phosphorylation in vitro as well as in vivo occurs primarily within the C-terminal half of the factor, and is caused by a cytosolic 40-kDa protein serine kinase. In contrast to other plant basic leucine-zipper motif factors, phosphorylation of CPRF2 does not alter its DNA binding activity. Therefore, we discuss alternative functions of the light-dependent phosphorylation of CPRF2 including the regulation of its nucleocytoplasmic partitioning.

Dynamic properties of endogenous phytochrome A in Arabidopsis seedlings

The dynamic behavior of phytochrome A (phyA) in seedlings of the model plant Arabidopsis was examined by in vivo spectroscopy and by western and northern blotting. Rapid accumulation of phyA was observed, reaching a steady state after 3 d. Both red and far-red light initiated a rapid destruction of the far-red-light-absorbing form of phytochrome (Pfr); the apparent half-life was only 4-fold longer in far-red than in red light. Furthermore, the Pfr-induced destruction of the red-light-absorbing form of phytochrome (Pr) of phyA occurred in darkness with a rate identical to that of Pfr destruction. A 2-fold decrease in mRNA abundance was observed after irradiation, irrespective of the applied light quality. However, reaccumulation occurred rapidly after far-red but slowly after red irradiation, indicating different modes of regulation of phytochrome expression after light-dark transitions depending on the light quality of the preceding irradiation. The wavelength dependency of the destruction rates was distinct from that of mustard, a close relative of Arabidopsis, and was explained on the basis of Pfr-induced Pr destruction and a simple kinetic two-step model. No dark reversion was detectable in the destruction kinetics after a red pulse. From these data we conclude that Arabidopsis phyA differs significantly in several aspects from other dicot phytochromes.

Antimicrobial effect of camphorated chloroxylenol (ED 84) in the treatment of infected root canals

During and after chemomechanical preparation, particularly before the definitive filling of an infected root canal, a temporary intracanal dressing with an antimicrobial activity is generally indicated. Therefore, the aim of this study was to investigate the antimicrobial effect of ED 84, a liquid root canal disinfectant containing chloroxylenol (10%) and camphor (15%), against selected test organisms (Staphylococcus aureus, Streptococcus faecalis, Escherichia coli, and Candida albicans) both in vitro and under clinical conditions, using extracted teeth. With a contact time of 180 min between undiluted ED 84 and the four bacterial suspensions in the canal, there was a 2 to 3 log reduction in the number of organisms. Under in vitro conditions, the reduction was even greater than 3 logs. When using a liquid medication as a temporary root canal dressing for a duration of approximately 2 days, ED 84 can definitely be used.

[Validation of a diagnostic scoring system (Ohmann score) in acute appendicitis]

A diagnostic scoring system, recently published by Ohmann et al. in this journal, was validated by analyzing the clinicopathological data of a consecutive series of 2,359 patients, admitted for suspicion of acute appendicitis. The results of the scoring system were compared to the results of clinical evaluation by junior (provisional) and senior surgeons (final clinical diagnosis). To assess the diagnostic ability of the score, the accuracy and positive predictive value were defined as the major diagnostic performance parameters; the rate of theoretical negative laparotomies and that of diagnostic errors served as the major procedural performance parameters. Of 2,359 patients admitted for suspected acute appendicitis, 662 were proven to have acute appendicitis by histology, for a prevalence of 28%. The overall sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the provisional clinical diagnosis were 0.50, 0.94, 0.77, 0.83, and 0.82; 0.93, for the score 0.63, 0.93, 0.77, 0.86 and 0.84, and for the final clinical diagnosis 0.90, 0.94, 0.85, 0.96, and 0.93, respectively. Of the main diagnostic performance parameter, the accuracy of the score was significantly better than that of provisional clinical diagnosis (P < 0.05, chi 2 test). The score yielded a rate of negative appendecomies and laparotomies of 14.3 and 12.3%. With respect to the rate of overlooked cases of acute apendicitis, the score demonstrated a superior performance, with only 6 cases missed (0.9%). However, the number of patients with acute appendicitis, including those with perforated disease, who were not identified by the score, was almost four times that of the final clinical diagnosis (245 vs 63). With regard to the main procedural performance parameter, the score resulted in a significantly smaller number of diagnostic errors than the provisional clinical investigator (P < 0.05, chi 2 test). The results of this study indicate that the diagnostic scoring system might be helpful when experienced investigators or additional diagnostic modalities such as ultrasonography are not available. It may therefore be of value in the preclinical evaluation of patients with suspected acute appendicitis and may be instrumental as a quality control tool and in clinical guidelines.

Comparison of cutting efficiency and instrumentation of curved canals with nickel-titanium and stainless-steel instruments

The cutting efficiency and the effects of instrumentation on curved canal shape of both stainless-steel and nickel-titanium nonstandardized ProFile Series 29 hand instruments and stainless-steel Flexoreamer were investigated under standardized conditions. Concerning cutting efficiency in rotary motion, the Flexoreamer had significantly (p < 0.01) greater cutting efficiency than stainless-steel ProFiles and nickel-titanium ProFiles. Changes in the canal shape differed significantly between the different instruments at all measuring points (p < 0.001). After instrumentation with Flexoreamers with inclusion of two half-sizes (#17 and #22), there were fewer undesirable changes in canal shape compared with both stainless-steel and nickel-titanium ProFile Series 29 instruments. In this study, it seemed that flexible stainless-steel instruments with noncutting tips were superior to the nonstandardized ProFile Series 29 instruments with regard to cutting efficiency and instrumentation of curved canals.

[Can diagnostic scoring systems help decision making in primary care of patients with suspected acute appendicitis?]

BACKGROUND AND OBJECTIVE

To assess two recently developed scoring systems with respect to making or excluding the diagnosis of acute appendicitis.

PATIENTS AND METHODS

Data on 2359 patients with typical signs of acute appendicitis (AA) were analysed, the results of two diagnostic scoring systems being compared with the diagnosis made by an experienced surgeon.

RESULTS

AA was confirmed in 662 of the 22,359 patients (prevalence 28%). Sensitivity, specificity, positive and negative predictive values and overall accuracy for diagnosis with the Ohmann scoring system were 0.63, 0.93, 0.77, 0.86 and 0.84; with the Eskelinen score the values were 0.79, 0.85, 0.68, 0.81 and 0.835; and by the surgeon they were 0.90, 0.94, 0.85, 0.96 und 0.93. The negative appendectomy or laparotomy rate was 14.3 an 12.3 respectively with the Ohmann score, 29.5 and 26.6 with the Eskelinen score. The numbers of potential and of nondiagnosed perforations were 41% and 37% respectively with the Ohman score and 26.6% and 16.3% with the Eskelinen score. The number of missed cases of AA was lowest with the Ohman scoring system, compared with 1.8% for the surgeon. After excluding AA, both scoring systems had a specificity of -0.99, with a positive probability rate of at least 27 (Eskelinen score) up to 87 (Ohman score).

CONCLUSION

Both diagnostic scoring systems are better for excluding than correctly diagnosing AA; the decision to exclude could be made with a high degree of accuracy. Either scoring system may therefore be used in primary care of patients suspected of AA to help decide on referral to hospital.

Control of hypocotyl elongation in Arabidopsis thaliana by photoreceptor interaction

In order to test the interaction of different phytochromes and blue-light receptors, etiolated seedlings of wild-type Arabidopsis thaliana (L.) Heynh., a phytochrome (phy) B-overexpressor line (ABO), and the photoreceptor mutants phyA-201, phyB-5, hy4-2.23n, fha-1, phyA-201/phyB-5, and phyA-201/hy4-2.23n were exposed to red and far-red light pulses after various preirradiations. The responsiveness to the inductive red pulses is primarily mediated by phyB which is rather stable in its far-red-absorbing form as demonstrated by a very slow loss of reversibility. Without preirradiation the red pulses had an impact on hypocotyl elongation only in PHYA mutants but not in the wild type. This indicates a suppression of phyB function by the presence of phyA. Preirradiation with either far-red or blue light resulted in an inhibition of hypocotyl elongation by red pulses in the wild type. Responsiveness amplification by far-red light is mediated by phyA and disappears slowly in the dark. The extent of responsiveness amplification by blue light was identical in the wild type and in the absence of phyA, or the cryptochromes cryl (hy4-2.23n) or cry2 (fha-1). Therefore, we conclude that stimulation of phyB by blue light preirradiation is either mediated by an additional still-unidentified blue-light-absorbing pigment or that phyA, cry1 and cry2 substitute for each other completely. Both blue and red preirradiation established responsiveness to red pulses in phyA-201/phyB-5 double mutants. These results demonstrate that inhibition of hypocotyl elongation by red pulses is not only mediated by phyB but also by a phytochrome(s) other than phyA and phyB.

Nuclear import of the parsley bZIP transcription factor CPRF2 is regulated by phytochrome photoreceptors

In plants, light perception by photoreceptors leads to differential expression of an enormous number of genes. An important step for differential gene expression is the regulation of transcription factor activities. To understand these processes in light signal transduction we analyzed the three well-known members of the common plant regulatory factor (CPRF) family from parsley (Petroselinum crispum). Here, we demonstrate that these CPRFs, which belong to the basic- region leucine-zipper (bZIP) domain-containing transcription factors, are differentially distributed within parsley cells, indicating different regulatory functions within the regulatory networks of the plant cell. In particular, we show by cell fractionation and immunolocalization approaches that CPRF2 is transported from the cytosol into the nucleus upon irradiation due to action of phytochrome photoreceptors. Two NH2-terminal domains responsible for cytoplasmic localization of CPRF2 in the dark were characterized by deletion analysis using a set of CPRF2-green fluorescent protein (GFP) gene fusion constructs transiently expressed in parsley protoplasts. We suggest that light-induced nuclear import of CPRF2 is an essential step in phytochrome signal transduction.

In vivo characterization of chimeric phytochromes in yeast

Phytochromes are plant photoreceptors that play a major role in photomorphogenesis. Two members of the phytochrome family have been characterized in some detail. Phytochrome A, which controls very low fluence and high irradiance responses, is rapidly degraded in the light, forms sequestered areas of phytochrome (SAPs), and does not exhibit dark reversion in monocotyledonous seedlings. Phytochrome B mediates red/far-red reversible responses, is stable in the light, and does not form SAPs. We report on the behavior in yeast of the phytochrome apoproteins of rice PHYA, tobacco PHYB, and chimeric PHYAB and PHYBA and on the behavior of the respective holoprotein adducts after assembly with phycocyanobilin chromophore (PHY*). SAP-like formation in yeast was not observed for PHYB, but was detectable for PHYA, PHYAB, and PHYBA. Rice PHYA* did not undergo dark reversion in yeast. Surprisingly, all other tested phytochrome constructs did exhibit dark reversion, including chimeric phytochromes with a short N-terminal part of tobacco PHYB or parsley PHYA fused to rice PHYA. Furthermore, the proportion of phytochrome undergoing dark reversion and the rate of reversion were increased for both the N terminus-swapped constructs and PHYBA*. These results are discussed with respect to structure/function analysis of phytochromes A and B.

Protein purification with C-terminal fusion of maltose binding protein

For affinity-chromatography-based purification of proteins that are prone to abnormal termination of translation or that may not be modified at their N-termini, affinity tags are needed which can be fused to the C-terminus. In this publication we describe that maltose binding protein (MBP) fused to the C-terminus of the plant photoreceptor phytochrome B allows purification of the fusion protein via amylose affinity chromatography. After overexpression in yeast a 125-fold enrichment could be achieved. The spectral properties of phytochrome B were not impaired by the fusion and purification. These results demonstrate that not only the widely used N-terminal fusions of MBP but also C-terminal fusions can be employed for protein purification.

The blue light receptor cryptochrome 1 can act independently of phytochrome A and B in Arabidopsis thaliana

Blue light responses in higher plants can be mediated not only by specific blue light receptors, but also by the red/far-red photoreversible phytochrome system. The question of interdependence between these photoreceptors has been debated over many years. The availability of Arabidopsis mutants for the blue light receptor CRY1 and for the two major phytochromes phyA and phyB allows a reinvestigation of this question. The analysis of photocontrol of seed germination, inhibition of hypocotyl growth and anthocyanin accumulation clearly demonstrates that (i) phyA shows a strong control in blue light responses especially at low fluence rates; (ii) phyB mediated induction reactions can be reversed by subsequent blue light irradiations; and (iii) CRY1 mediates blue light controlled inhibition of hypocotyl growth only at fluence rates higher than 5 mumol m-2s-1 and independently of phytochrome A and B.

Safety, pharmacokinetics and biological activity of enlimomab (anti-ICAM-1 antibody): an open-label, dose escalation study in patients hospitalized for acute stroke

BACKGROUND AND PURPOSE

To obtain information on the safety, pharmacokinetics and biological activity of enlimomab (anti-ICAM-1 antibody) in stroke patients.

METHODS

An open, uncontrolled, dose titration study was conducted in 32 patients hospitalized for stroke. Patients received one of four fixed dose regimens of enlimomab. A loading dose of enlimomab administered within 24 h of the onset of stroke symptoms was followed by four daily maintenance doses; total doses ranged from 140 to 480 mg.

RESULTS

The pharmacokinetic target levels (enlimomab serum levels of >/=10 microg/ml) were consistently achieved in all patients receiving dose regimens III and IV. Non-serious adverse events thought to be causally related to enlimomab administration included headache, vomiting and extrasystoles. Serious events occurred in 14 patients, including pneumonia, sepsis, cardiac failure and cardiac arrest. The only serious adverse event considered to be related to enlimomab administration was an anaphylactoid reaction, in a patient who received an unfiltered loading dose of antibody; the patient recovered. The overall mortality in the study was 15.6% and the 30-day mortality was 12.5%. There was no increase in the frequency of adverse events with increasing doses of enlimomab.

CONCLUSIONS

Doses of enlimomab between 140 and 480 mg administered over 5 days did not increase the risk of adverse events in patients with ischaemic or haemorrhagic stroke during an observation period of 30 +/- 10 days. A loading dose of 160 mg followed by four daily maintenance doses of 40 mg appears to be suitable for further study.

An Arabidopsis mutant hypersensitive to red and far-red light signals

A new mutant called psi2 (for phytochrome signaling) was isolated by screening for elevated activity of a chlorophyll a/b binding protein-luciferase (CAB2-LUC) transgene in Arabidopsis. This mutant exhibited hypersensitive induction of CAB1, CAB2, and the small subunit of ribulose-1,5-bisphosphate carboxylase (RBCS) promoters in the very low fluence range of red light and a hypersensitive response in hypocotyl growth in continuous red light of higher fluences. In addition, at high- but not low-light fluence rates, the mutant showed light-dependent superinduction of the pathogen-related protein gene PR-1a and developed spontaneous necrotic lesions in the absence of any pathogen. Expression of genes responding to various hormone and environmental stress pathways in the mutant was not significantly different from that of the wild type. Analysis of double mutants demonstrated that the effects of the psi2 mutation are dependent on both phytochromes phyA and phyB. The mutation is recessive and maps to the bottom of chromosome 5. Together, our results suggest that PSI2 specifically and negatively regulates both phyA and phyB phototransduction pathways. The induction of cell death by deregulated signaling pathways observed in psi2 is reminiscent of retinal degenerative diseases in animals and humans.

CPRF4a, a novel plant bZIP protein of the CPRF family: comparative analyses of light-dependent expression, post-transcriptional regulation, nuclear import and heterodimerisation

Several DNA-binding proteins with conserved basic region/leucine zipper domains (bZIP) have been isolated from parsley. They all recognise defined ACGT-containing elements (ACEs), including ACE(PcCHSII) in the Light Regulatory Unit LRU1 of the CHS promoter which confers light responsiveness. A new member of this Common Plant Regulatory Factor (CPRF) family, designated CPRF4a, has been cloned, which displays sequence similarity to HBP-1a from wheat, as well as to other plant bZIP proteins. CPRF4a specifically binds as a homodimer to ACE(PcCHSII) and forms heterodimers with CPRF1 but not with CPRF2. In adult parsley plants, CPRF2 and CPRF4a mRNAs are found in all tissues and organs in which the chalcone synthase gene CHS is expressed. In protoplasts from suspension cultured cells, UV irradiation (290-350 nm) did not cause an increase in levels of CPRF1, CPRF2, or CPRF4a mRNA, whereas the corresponding CPRF proteins accumulated within 15 min of light treatment. Furthermore, the rapid light-mediated increase of CPRF proteins was insensitive to transcriptional inhibitors, suggesting that a post-transcriptional mechanism controls CPRF accumulation. CPRFs as well as Arabidopsis thaliana G-box binding factors (GBFs) are selectively transported from the cytosol into the nucleus, as shown in an in vitro nuclear transport system prepared from evacuolated parsley protoplasts, indicating that cytosolic compounds are involved in regulated nuclear targeting of plant bZIP factors.

Mode of phytochrome B action in the photoregulation of seed germination in Arabidopsis thaliana

Arabidopsis thaliana seeds imbibed for a short duration show phytochrome B (PhyB)-specific photo-induction of germination. Using this system, the relationship was determined between the amount of PhyB in seeds and photon energy required for PhyB-specific germination in two transgenic Arabidopsis lines transformed with either the Arabidopsis PhyB cDNA (ABO) or the rice PhyB cDNA (RBO). Immunochemical detection of PhyB apoprotein (PHYB) showed that the expression level of PHYB in ABO seeds was at least two times higher than that in the wild-type seeds, but in RBO seeds the PHYB level was indistinguishable from that in wild-type seeds. The photon fluence required for induction and photoreversible inhibition of germination was examined using the Okazaki large spectrograph. At the wavelengths of 400-710 nm, the ABO seeds required significantly less photon fluence than wild-type seeds for induction of germination, whereas the RBO seeds required similar fluence to wild-type seeds. A critical threshold wavelength for either induction or inhibition of germination of ABO seeds shifted towards the longer wavelengths relative to wild-type seeds. By assuming that PhyA and PhyB are similar in their photochemical parameters, amounts of Pfr at each wavelength were calculated. The photon fluence required for 50% germination was equivalent to the fluence generating a Pfr/Ptot ratio of 0.21-0.43 in wild-type seeds, and of 0.035-0.056 in ABO seeds. These results indicate that PhyB-specific seed germination is not strictly a function of the Pfr/Ptot ratio, but is probably a function of the absolute Pfr concentration.

Transcription of Arabidopsis and wheat Cab genes in single tobacco transgenic seedlings exhibits independent rhythms in a developmentally regulated fashion

Transcription of Cab genes has been previously shown to be regulated by a circadian oscillator coupled to the red light-absorbing plant photoreceptor phytochrome in various plant species. In addition, it has recently been suggested that rhythmic expression of the Cab genes could also be affected by a phytochrome-independent circadian oscillator in a developmentally regulated fashion. This study has shown that a red light-insensitive oscillator and a phytochrome-coupled circadian clock indeed coregulate the oscillating expression of individual Cab genes at the level of transcription at an early developmental stage. The study involved analysing the expression patterns of transgenes, containing short fragments of the Arabidopsis thaliana Cab2 or the wheat Cab-1 promoter fused to the firefly luciferase reporter gene, by a video-imaging system in single, etiolated tobacco seedlings. Germination and red/far-red light treatments applied between 12 and 36 h after sowing lead to the appearance of two independent circadian rhythms. These rhythms coexist, both exhibiting period lengths close to 25 h but phased differently. However, repeated red-light treatments given 60 h or later after sowing synchronize these free-running rhythms and induce a single new circadian oscillation. These data indicate that both oscillators regulate the expression of the Cab genes studied at the level of transcription and that the cis-acting element(s) of the wheat Cab-1 and A. thaliana Cab2 genes mediating these responses are located on short, 250 bp promoter regions. Furthermore, these red-light induced rhythms are also inducible by far-red light treatments alone. Therefore, in tobacco, the phytochrome-coupled oscillator is regulated, at least partially, by the very low fluence response of phytochrome A.

Developmental and light-dependent changes of the cytosolic chaperonin containing TCP-1 (CCT) subunits in maize seedlings, and the localization in coleoptiles

The cytosolic chaperonin containing TCP-1 (CCT) is known to keep fold cytoskeletal proteins and is involved in the proper organization of the cytoskeleton. These studies are based on the assumption that growth responses linked to structural rearrangement of the plant cytoskeleton include the action of CCT and the need for newly synthesized tubulin. The presence of the alpha- and epsilon-subunits of CCT was investigated in soluble fractions of protein extracts from maize mesocotyls and coleoptiles at distinct growth stages. The CCT-subunits, tubulins and actin decreased in the coleoptile in response to far-red light. In addition, independent from light treatment, the amount of CCT epsilon abundance declined with age in coleoptiles and mesocotyls between 2 and 4.5 days after sowing. In contrast to CCT epsilon, no significant light regulation of CCT alpha was found in the mesocotyl. In two day old, light-grown rapidly elongating coleoptiles part of the CCT alpha subunit and the bulk of actin and tubulin was found shifted into fractions of high molecular weight complexes when compared to slowly elongating, dark grown coleoptiles. In 4.5 day old, etiolated and elongating coleoptiles, part of both CCT-subunits and cytoskeleton proteins were found in fractions of high molecular weight. A complete disappearance of these polypeptides was observed in old far-red irradiated growth-arrested coleoptiles. CCT epsilon was found to be colocalized to microtubular structures and to the nucleus. We conclude from our data that abundance of CCT-subunits in soluble extracts is dependent on age and light treatment, but independent from the growth stage of mesocotyl and coleoptile.