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At least 163 records · Page 9Linked to original sources
PubMed2005

Light quantity and quality induce shade-avoiding plasticity in a marine macroalga.

Light-induced plasticity in plant morphology is considered adaptive in terrestrial habitats that vary in light, but remains unexplored for marine habitats. This is despite similar modes of growth, development and photosynthetic equipment in terrestrial and marine photoautotrophs and similarly dynamic light environments. We tested whether manipulations of light quantity and quality induce morphological plasticity in the marine macroalga, Asparagopsis armata. Using multivariate analyses (principal components analyses and multivariate analyses of covariance), we show that correlated morphological traits underlie a fundamental growth strategy characterized by the production of phalanx and guerrilla phenotypes in environments that mimic light and shade respectively. This foraging response is not under simple genetic or environmental control, but influenced by interactions between genotype and environment. Evidence of plasticity and genetic variation in plasticity in a marine modular organism generates additional, testable hypotheses on the ecological consequences of variation in growth form that may further explain the evolution of plasticity.

Adaptation, Physiological↗
PubMed1996

Regulation of the Arabidopsis thaliana aquaporin gene AthH2 (PIP1b).

Arabidopsis thaliana was transformed with constructs composed of the aquaporin AthH2 promoter and the coding sequence of beta-glucuronidase (GUS) as reporter gene. The transgenic plants obtained were treated with different light qualities or phytohormones and the activity of the AthH2 promoter was determined in situ using a specific GUS assay. With blue light (400-550 nm) and white light, significant activation of the promoter was observed. The same was true for the application of gibberellic acid (GA) and abscisic acid (ABA). In contrast, red light and indole-3-acetic acid (IAA) had only minor effects on the promoter activity. The significance of sequence elements with relation to GA or ABA was confirmed by deletion analyses of the AthH2 promoter. Likewise, a promoter segment with importance for hydathoid specific expression was identified.

Arabidopsis↗
PubMed1992

Synthesis of the early light-inducible protein is controlled by blue light and related to light stress.

The early light-inducible proteins (ELIPs) are expressed in developing plants in the first hours of the greening process. Here we report that strong light causing photoinhibition of photosynthesis also induces ELIP transcription and accumulation of the protein in mature green pea plants. Accumulation of ELIP transcript is induced in plants exposed to light intensities above 500 E/m2.s (E, einstein) and is maximal at approximately 1500 E/m2.s. The ELIP mRNA level increases in correlation with the degree of photoinhibition. The increase in ELIP level in the thylakoid membranes parallels the decrease in the amount of D1 protein of the photosystem II reaction center. Examination of ELIP induction as a function of light quality demonstrates that ELIP transcription is specifically induced by blue (410-480 nm) but not by red or far-red light. The level of blue light-induced ELIP transcript is significantly repressed by low-intensity red light. However, the accumulation of ELIP translation product is related to the total amount of blue and red light energy absorbed.

Journal Article↗
PubMed1995

Effects of lensed-indirect and parabolic lighting on the satisfaction, visual health, and productivity of office workers.

A pre- and post-renovation survey evaluated the reactions of office workers to two office lighting systems: a parabolic downlighting system and a ceiling suspended, lensed-indirect uplighting system. Questionnaire data on work content, perception of ambient environmental conditions (including office lighting), work-related health symptoms, job stress, job satisfaction, and self-reported productivity, and environmental data on illumination, air temperature, and relative humidity were collected. The lensed-indirect lighting system was more favourably rated on several subjective lighting impressions scales, and for computer work workers reported fewer screen glare problems, and fewer and less frequent problems with tired eyes and eye focusing. Productivity was less hindered by the lensed-indirect lighting, and satisfaction with office lighting and ratings of lighting quality were significantly higher for this system. These reactions were not associated with any differences in levels of illumination between the lighting systems. Ratings of lighting satisfaction and lighting importance were inversely related. Overall, some two-thirds of workers indicated a preference for working under the lensed-indirect lighting system.

Adult↗
PubMed2003

Effect of embryonic photostimulation on the posthatch growth of turkey poults.

Artificial illumination, including light quality, is important in modern meat-type poultry management. In the present study, the effect of in ovo monochromatic green light photostimulation on posthatch growth of turkey poults was investigated. In experiment 1, 182 turkey eggs were divided into two light treatment groups (n = 91). The first group was intermittently photostimulated (3 min on and 3 min off) with green light provided by five light-emitting diodes (LED) per egg at 0.1 W/m2 at the upper eggshell surface. The second group was incubated in the dark and served as the control. Posthatch BW were recorded at 0, 2, 6, 13, 20, 28, 35, and 59 d of age. A heavier BW, occurring at 28 d of age and persisting until the end of the experiment (59 d of age), was observed in the in ovo green light stimulated females as compared to their corresponding controls. In experiment 2, 273 turkey eggs were divided into three light treatment groups (n = 91). The first group was intermittently photostimulated (15 min on and 15 min off) with green light provided by seven LED per egg at 0.14 W/m2. The second group was photostimulated with white light provided by one mini-incandescent lamp per egg at light intensity and schedule similar to the first group. Eggs of the third group were incubated in the dark and served as controls. Posthatch BW were recorded at 0, 7, 14, 28, 42, 56, and 79 d of age. No differences were found among the BW of males incubated under different light conditions. As in experiment 1, female turkeys with stimulated green light in ovo had greater BW compared to their corresponding control and white light groups from 28 d of age until termination of the experiment at 79 d of age. Breast muscle weight was greater in female turkeys incubated under green light when compared to white and dark incubation treatment groups. We suggest that in ovo green light photostimulation enhances the posthatch BW of female turkey poults.

Aging↗
PubMed1992

The effect of color temperature of lighting sources on the autonomic nervous functions.

The present study was designed to investigate the effects of color temperature of lighting sources on the heart rate variability. Eight male students volunteered as subjects. The heart rate variability during task and rest sessions were estimated under nine different lighting environments consisting of three levels of color temperature (3000 degrees K, 5000 degrees K and 6700 degrees K) and three levels of illuminance (1001x, 3001x and 9001x). The lighting condition caused no effect on the mean heart rate. On the other hand, the power spectrum of heart rate was significantly influenced by the lighting conditions. The respiratory sinus arrhythmia component and Mayer wave related sinus arrhythmia component of the power spectrum increased under higher color temperature conditions. Judging from the consistency of heart rate level, the balance between the effects of parasympathetic and sympathetic nervous systems remained at a constant level irrespective of lighting quality and intensity. Therefore, both parasympathetic and sympathetic nervous functions were concluded to be enhanced under higher color temperature conditions. The light with higher color temperature was considered to activate the autonomic nervous function more than the light of lower color temperature. The effect of color temperature was much remarkable in the rest session comparing with the task session. This fact was discussed from the viewpoint of color temperature effect in environmental lighting.

Adult↗
PubMed1988

[Control of chlorophyll a synthesis by phytochrome and cryptochrome in the red alga Corallina elongata Ellis et Soland].

Chlorophyll a synthesis in the red alga Corallina elongata is controlled by phytochrome and by a specific blue light photoreceptor. Although the estimated photoequilibrium of phytochrome is similar in blue and red light, the amount of chlorophyll accumulated is greater in blue light, which implies the action of cryptochrome, according to the criteria for the specific blue light photoreceptor involvement. The amount of chlorophyll synthesized is greater when the level of photoequilibrium approaches 65% (in blue and red light) than with higher levels (72.7% in white light and 70.8% in green light). The action of phytochrome is demonstrated by the induction of chlorophyll synthesis after red pulses and the reversion after far red pulses. The reversion is not complete but the percentage of reversibility is high (85-90%). The amount of chlorophyll accumulated is greater in darkness after the application of red light pulses than in white light after the same light pulses. The induction of chlorophyll synthesis is greater after red pulses than after continuous red light. The existence of a fast destruction of chlorophyll in continuous light is observed. This destruction is greater in the high photoequilibrium of phytochrome (70-72%). The turnover times and the induction mechanism of chlorophyll synthesis must be very fast. This indicates the existence of a possible rapid adaptation to the change in light quality and intensity in the marine system.

Chlorophyll↗
PubMed1997

Light-dependent regulation of carotenoid biosynthesis occurs at the level of phytoene synthase expression and is mediated by phytochrome in Sinapis alba and Arabidopsis thaliana seedlings.

In chloroplasts, carotenoids are essential pigments involved in photosynthesis. During-photomorphogenesis, a coordinated increase in the amounts of chlorophylls and carotenoids, in conjugation with other components, leads to the formation of a functional photosynthetic apparatus. To investigate the regulation of carotenoid biosynthesis during this process at the molecular level, GGPS, PSY and PDS cDNAs have been cloned from white mustard (Sinapis alba L). GGPS encodes a key enzyme in plastid isoprenoid metabolism, while the products of PSY and PDS catalyse the subsequent steps in carotenoid biosynthesis. Due to the low mRNA levels of the genes involved, the use of a RT-PCR protocol was necessary to measure gene expression during photomorphogenesis. With light, there is an up-regulation of PSY expression, the first gene within the carotenoid biosynthetic pathway, while PDS and GGPS expression levels remain constant. Treatment with different light qualities reveals a phytochrome-mediated regulation of PSY expression in developing white mustard seedlings. To obtain more detailed information on the light-regulation, Arabidopsis thaliana wild-type and phytochrome mutants were utilized. Continuous far-red and red light both increase the expression of PSY in wild-type seedlings, demonstrating that both light-labile and light-stable phytochromes are involved in PSY regulation. The response to far-red light is completely abolished in the phyA mutant, showing that PHYA mediates the increase in PSY transcript levels under these light conditions. In the phyB mutant, the red light response is normal, indicating that PSY expression is not controlled by PHYB but by other light-stable phytochromes. Measurement of chlorophylls and carotenoids under the same light regimes shows that the up-regulation of PSY expression does not necessarily result in an increase of the carotenoid content. Only those light conditions which allow chlorophyll biosynthesis lead to a significant increase of the carotenoid content. Therefore, it is proposed that up-regulation of PSY mRNA levels leads to an increased capacity for the formation of carotenoids. However, this only takes place under light conditions leading to protochlorophyllide photoconversion.

Alkyl and Aryl Transferases↗
PubMed2005

Conservation and divergence of light-regulated genome expression patterns during seedling development in rice and Arabidopsis.

Genome-wide 70-mer oligonucleotide microarrays of rice (Oryza sativa) and Arabidopsis thaliana were used to profile genome expression changes during light-regulated seedling development. We estimate that the expression of approximately 20% of the genome in both rice and Arabidopsis seedlings is regulated by white light. Qualitatively similar expression profiles from seedlings grown under different light qualities were observed in both species; however, a quantitatively weaker effect on genome expression was observed in rice. Most metabolic pathways exhibited qualitatively similar light regulation in both species with a few species-specific differences. Global comparison of expression profiles between rice and Arabidopsis reciprocal best-matched gene pairs revealed a higher correlation of genome expression patterns in constant light than in darkness, suggesting that the genome expression profile of photomorphogenesis is more conserved. Transcription factor gene expression under constant light exposure was poorly conserved between the two species, implying a faster-evolving rate of transcription factor gene expression in light-grown plants. Organ-specific expression profiles during seedling photomorphogenesis provide genome-level evidence for divergent light effects in different higher plant organs. Finally, overrepresentation of specific promoter motifs in root- and leaf-specific light-regulated genes in both species suggests that these cis-elements are important for gene expression responses to light.

Arabidopsis↗
PubMed2006

CONSTITUTIVELY PHOTOMORPHOGENIC1 is required for the UV-B response in Arabidopsis.

CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) is a negative regulator of photomorphogenesis in Arabidopsis thaliana. COP1 functions as an E3 ubiquitin ligase, targeting select proteins for proteasomal degradation in plants as well as in mammals. Among its substrates is the basic domain/leucine zipper (bZIP) transcription factor ELONGATED HYPOCOTYL5 (HY5), one of the key regulators of photomorphogenesis under all light qualities, including UV-B responses required for tolerance to this environmental threat. Here, we report that, in contrast with the situation in visible light, COP1 is a critical positive regulator of responses to low levels of UV-B. We show that in the cop1-4 mutant, flavonoid accumulation and genome-wide expression changes in response to UV-B are blocked to a large extent. COP1 is required for HY5 gene activation, and both COP1 and HY5 proteins accumulate in the nucleus under supplementary UV-B. SUPPRESSOR OF PHYTOCHROME A-105 family proteins (SPA1 to SPA4) that are required for COP1 function in dark and visible light are not essential in the response to UV-B. We conclude that COP1 performs a specific and novel role in the plants' photomorphogenic response to UV-B, coordinating HY5-dependent and -independent pathways, which eventually results in UV-B tolerance.

Arabidopsis↗
PubMed2004

Phenotypic characterization of a photomorphogenic mutant.

Light is arguably the most important abiotic factor controlling plant growth and development throughout their life cycle. Plants have evolved sophisticated light-sensing mechanisms to monitor fluctuations in light quality, intensity, direction and periodicity (day length). In Arabidopsis, three families of photoreceptors have been identified by molecular genetic studies. The UV-A/blue light receptors cryptochromes and the red/far-red receptors phytochromes control an overlapping set of responses including photoperiodic flowering induction and de-etiolation. Phototropins are the primary photoreceptors for a set of specific responses to UV-A/blue light such as phototropism, chloroplast movement and stomatal opening. Mutants affecting a photoreceptor have a characteristic phenotype. It is therefore possible to determine the specific developmental responses and the photoreceptor pathway(s) affected in a mutant by performing an appropriate set of photobiological and genetic experiments. In this paper, we outline the principal and easiest experiments that can be performed to obtain a first indication about the nature of the photobiological defect in a given mutant.

Arabidopsis↗
PubMed1995

Photosynthesis. Regulation by redox signalling.

Photosynthesis is light-driven redox chemistry. Molecular redox signalling, the coupling of gene expression to electron transfer, is now implicated in the adaptation of photosynthesis to variation in light quality and quantity.

Bacterial Proteins↗
PubMed1992

Differential effect of ultraviolet-B radiation on certain metabolic processes in a chromatically adapting Nostoc.

The impact of UV-B radiation on growth, pigmentation and certain physiological processes has been studied in a N2-fixing chromatically adapting cyanobacterium, Nostoc spongiaeforme. A brownish form (phycoerythrin rich) was found to be more tolerant to UV-B than the blue-green (phycocyanin rich) form of N. spongiaeforme. Continuous exposure to UV-B (5.5 W m-2) for 90 min caused complete killing of the blue-green strain whereas the brown strain showed complete loss of survival after 180 min. Pigment content was more strongly inhibited in the blue-green strain than in the brown. Nitrogenase activity was completely abolished in both strains within 35 min of UV-B treatment. Restoration of nitrogenase occurred upon transfer to fluorescent or incandescent light after a lag of 5-6 h, suggesting fresh synthesis of nitrogenase. Unlike the above processes, in vivo nitrate reductase activity was stimulated by UV-B treatment, the degree of enhancement being significantly higher in the blue-green strain. Like the effect of UV-B on nitrogenase, 14CO2 uptake was also completely abolished by UV-B treatment in both strains. Our findings suggest that UV-B may produce a deleterious effect on several metabolic activities of cyanobacteria, especially in cells lacking phycoerythrin. Strains containing phycoerythrin appear to be more tolerant to UV-B, probably because of their inherent property of adapting to a variety of light qualities.

Adaptation, Physiological↗
PubMed1995

The gene family encoding the fucoxanthin chlorophyll proteins from the brown alga Macrocystis pyrifera.

Six members of a multigene family encoding polypeptide constituents of the fucoxanthin, chlorophyll a/c protein complex from female gametophytes of the brown alga Macrocystis pyrifera have been cloned and characterized. The deduced amino acid sequences are very similar to those of fucoxanthin chlorophyll binding proteins (Fcp) from the diatom Phaeodactylum tricornutum and exhibit limited homology to chlorophyll a/b binding (Cab) polypeptides from higher plants. The primary translation products from the M. pyrifera fcp genes are synthesized as higher molecular weight precursors that are processed prior to their assembly into the Fcp complex. The presumed N-terminal 40-amino acid presequence of the Fcp precursor polypeptide has features resembling that of a signal sequence. This presequence may be required for the protein to transverse the endoplasmic reticulum that surrounds the plastid in brown algae. A subsequent targeting step would be required for the protein to cross the double membrane of the plastid envelope. M. pyrifera fcp transcripts are of two sizes, 1.2 and 1.6 kb. The size difference is accounted for by the length of the 3' untranslated region, which can be up to 1000 bases. Transcript abundance's of members of the fcp gene family are dependent on light quantity, light quality, or both. Transcript levels of one gene increased approximately five- to tenfold in thalli grown in low intensity relative to high intensity white or blue light. Transcripts from this gene also significantly increase in red light relative to blue light at equivalent light intensities.

Amino Acid Sequence↗
PubMed1998

Involvement of plasma membrane redox activity and calcium homeostasis in the UV-B and UV-A/blue light induction of gene expression in Arabidopsis.

UV and blue light are important regulators of plant gene expression and development. We investigated the signal transduction processes involved in the induction of chalcone synthase (CHS) and phenylalanine ammonia-lyase (PAL) gene expression by UV-B and UV-A/blue light in an Arabidopsis cell suspension culture. Experiments with electron transport inhibitors indicated that plasma membrane redox activity is involved in both signal transduction pathways. Calcium ionophore treatment stimulated expression of the TOUCH3 gene, and this induction was strongly antagonized by UV-A/blue and UV-B light, suggesting that both light qualities may promote calcium efflux from the cytosol. Consistent with this hypothesis, experiments with specific inhibitors indicated that UV-B and UV-A/blue light regulate calcium levels in a cytosolic pool in part via the action of specific Ca2+-ATPases. On the basis of these and previous findings, we propose that plasma membrane redox activity, initiated by photoreception, is coupled to the regulation of calcium release from an intracellular store, generating a calcium signal that is required to induce CHS expression.

Acyltransferases↗
PubMed2002

Light and shade in the photocontrol of Arabidopsis growth.

Plants have evolved sophisticated sensing mechanisms that operate through phytochromes, perceiving changes in the red:far-red ratio, which trigger morphological changes to avoid shade. The shade-avoidance response essentially redirects resources and growth potential from the leaf and storage organs into increased extension growth to optimize light capture by plants. Recent studies implicate ATHB-2, a homeodomain-leucine zipper transcription factor, as a regulator of shade-avoidance responses and establish a strong link between this factor and auxin signaling. The action of ATHB-2 is likely to generate changes in auxin distribution that produce distinct but coordinated effects on different cell types across the plant. Future studies should highlight how polarity of auxin transport is altered in response to light-quality changes.

Arabidopsis↗
PubMed1982

[Postnatal weight gain in albino mice under various light regimens].

The following experiments on male and female mice of the strain AB Jena Halle were designed to study the effect of various light regimens on the body weight during the postnatal development from birth to 60 days of age. Characteristic phases of the increase in weight appear in both cyclic illumination (12L:12D, 50 lux) and constant light (24 L, 50 lux). These phases are dependent upon the wavelength and the effective period of light. Such a phase is pronounced in the puberal period in which was found a relationship between the body weight and the wavelength. At the end of the experiments, remarkable low body weights appear in red exposition in both sexes, specially in the females. Continuous white or coloured light effects, in principle, a more distinctive sec-dimorphism of the body weight than 12L:12D, because the increase of the body weight of the males is higher in 24L: as in 12L: 12D. Female mice did not show such a reaction. It follows from the results that various light regimens and various light qualities influence the postnatal increase of body weight.

Animals↗
PubMed2000

Control of nuclear import and phytochromes.

The past year has brought significant changes in our understanding of the molecular mechanism of photoreceptor-regulated gene expression in higher plants. The light-quantity- and light-quality-dependent nuclear import of phytochromes, followed by the conformation-dependent direct interaction of these phytochromes with transcription factors, seems to play a major role in light-modulated plant growth and development.

Cell Nucleus↗