Low-intensity Red Light Research Articles

Dynamic Behaviour of Self-Diffraction in BacteriorhodopsinFilm

We investigate the dependences of the diffraction efficiency of thefirst order self-diffracted beam in bacteriorhodopsin (bR) films on theillumination time, the intensity and wavelength of the incident light.When the blue light (λ = 488 nm) and low intensity red light(λ = 632.8 nm) are incident on the bR filmrespectively, the diffraction efficiencies increase from zero to astable value with the illumination time. When the green light (λ = 533 nm) and high-intensity red light illuminate the bR filmrespectively, the diffraction efficiencies increase from zero to themaximum and then decrease to a stable value with the illumination time.Rise and decay times are dependent on the intensity and wavelength ofthe incident light. The maximal diffraction efficiency of the redlight is twice as high as that of the green light. The highestdiffraction efficiency of 5.4% is obtained at 633 nm. Thediffraction efficiency change with the time for the green light islarger than that for the blue and red light.

Light control of hliA transcription and transcript stability in the cyanobacterium Synechococcus elongatus strain PCC 7942.

The high-light-inducible proteins (HLIPs) of cyanobacteria are polypeptides involved in protecting the cells from high-intensity light (HL). The hliA gene encoding the HLIP from Synechococcus elongatus strain PCC 7942 is expressed in response to HL or low-intensity blue or UV-A light. In this study, we explore via Northern analysis details of the transcriptional regulation and transcript stability of the hliA gene under various light conditions. Transcript levels of the hliA gene increased dramatically upon a shift to HL or UV-A light to similar levels, followed by a rapid decrease in UV-A light, but not in HL, consistent with blue/UV-A light involvement in early stages of HL-mediated expression. A 3-min pulse of low-intensity UV-A light was enough to trigger hliA mRNA accumulation, indicating that a blue/UV-A photoreceptor is involved in upregulation of the gene. Low-intensity red light was found to cause a slight, transient increase in transcript levels (raising the possibility of red-light photoreceptor involvement), while light of other qualities had no apparent effect. No evidence was found for wavelength-specific attenuation of hliA transcript levels induced by HL or UV-A light. Transcript decay was slowed somewhat in darkness, and when photosynthetic electron transport was inhibited by darkness or treatment with DCMU, there appeared a smaller mRNA species that may represent a decay intermediate that accumulates when mRNA decay is slowed. Evidence suggests that upregulation of hliA by light is primarily a transcriptional response but conditions that cause ribosomes to stall on the transcript (e.g., a shift to darkness) can help stabilize hliA mRNA and affect expression levels.

CDNA Microarray Analysis of Gene Expression Profiles in Human Fibroblast Cells Irradiated with Red Light

In this paper, the cDNA microarray technique was used to investigate the gene expression profiles of human fibroblasts irradiated by low-intensity red light. Proliferation assays showed that the fibroblast HS27 cells responded with a curve effect to different doses of low-intensity red light irradiation at a wavelength of 628 nm. An optimal dose of 0.88 J per cm2 was chosen for subsequent cDNA microarray experiments. The gene expression profiles revealed that 111 genes were regulated by the red light irradiation and can be grouped into 10 functional categories. Most of these genes directly or indirectly play roles in the enhancement of cell proliferation and the suppression of apoptosis. Two signaling pathways, the p38 mitogen-activated protein kinase signaling pathway and the platelet-derived growth factor signaling pathway, were found to be involved in cell growth induced by irradiation of low-intensity red light. Several genes related to antioxidation and mitochondria energy metabolism were also found to express differentially upon irradiation. This study provides insight into the molecular mechanisms associated with the beneficial effects of red light irradiation in accelerating wound healing.

A new type of adaptation of the cyanobacterium Spirulina platensis to illumination conditions

Incubation of cells of the cyanobacterium Spirulina platensis under conditions of exposure to low-intensity (2-3 microE m-2 s-1) red light, which was predominantly absorbed by photosystem I (PS I), caused atypical adaptation changes. Invariable pigment composition and stoichiometry of photosystems was observed in the cells incubated under these conditions against the background of a decrease in the rate of photosynthetic fixation of CO2 (by one-half) and a 1.5-fold increase in the rate of dark respiration relative to cells incubated under conditions of exposure to green light. Comparison of these data with a high rate of dark relaxation of P700+ in the presence of diuron suggests that deficiency of reduced equivalents at the donor side of PS I in the Spirulina cells exposed to red light is compensated by electron supply from the respiratory chain NAD(P)H dehydrogenase complex.

The Effects of Low Intensity Red Laser Irradiation on Hatching Eggs in Chicken and Quail

Low intensity red (λ=633 nm) light was used on hatching poultry and quail eggs to determine its influence on embryonic and post-embryonic development. Certain regimens of hatching egg irradiation (p=0.1 mW/cm , t=60 c) 2 significantly increased hatching rates (3.66-4.05%, p<0.001) and decreased chick mortality (1.25-3.23%, p<0.05) for layer and broiler chickens compared to untreated controls (using industrial poultry farm conditions). Laser irradiation of hatching egg increased chick blood hemoglobin, changed (increased in embryo and decreased in postembryo period) liver peroxide levels and activated cytochrome P-450 enzyme system without adversely affecting liver energy metabolism.

Effects of red light on postischemic myocardium during reperfusion.

Effects of low-intensity red light on lipid peroxidation in isolated rat heart in the postischemic period were studied. It was established that both laser and wideband luminescent irradiation applied during reperfusion reduced the content of lipid peroxidation products in tissues to a near-control level. This effect is possibly associated with reactivation of antioxidant enzymes.

Effect of low-intensity luminescent radiation on recovery of heart function in postischemic period

We studied the effect of low-intensity red light on the contractile function of isolated heart in the postischemic period. The sources of luminescent radiation used in the study produced visible light of different spectral bandes and allowed to illuminate local regions of the myocardium.

Red light-induced suppression of gravitropism in moss protonemata

Moss protonemata are among the few cell types known that both sense and respond to gravity and light. Apical cells of Ceratodon protonemata grow by oriented tip growth which is negatively gravitropic in the dark or positively phototropic in unilateral red light. Phototropism is phytochrome-mediated. To determine whether any gravitropism persists during irradiation, cultures were turned at various angles with respect to gravity and illuminated so that the light and gravity vectors acted either in the same or in different directions. Red light for 24h (≥140nmol m−2s−1) caused the protonemata to be oriented directly towards the light. Similarly, protonemata grew directly towards the light regardless of light position with respect to gravity indicating that all growth is oriented strictly by phototropism, not gravitropism. At light intensities ≤100nmol m−2s−1, no phototropism occurs and the mean protonemal tip angle remains above the horizontal, which is the criterion for negative gravitropism. But those protonemata are not as uniformly upright as they would be in the dark indicating that low intensity red light permits gravitropism but also modulates the response. Protonemata of the aphototropic mutant ptr1 that lacks a functional Pfr chromophore, exhibit gravitropism regardless of red light intensity. This indicates that red light acts via Pfr to modulate gravitropism at low intensities and to suppress gravitropism at intensities ≥140nmol m−2s−1.

Phytochromes and cryptochromes in the entrainment of the Arabidopsis circadian clock.

Circadian clocks are synchronized by environmental cues such as light. Photoreceptor-deficient Arabidopsis thaliana mutants were used to measure the effect of light fluence rate on circadian period in plants. Phytochrome B is the primary high-intensity red light photoreceptor for circadian control, and phytochrome A acts under low-intensity red light. Cryptochrome 1 and phytochrome A both act to transmit low-fluence blue light to the clock. Cryptochrome 1 mediates high-intensity blue light signals for period length control. The presence of cryptochromes in both plants and animals suggests that circadian input pathways have been conserved throughout evolution.

GROWTH AND FLOWER DEVELOPMENT IN ROSES AS AFFECTED BY LIGHT

Growth and flowering of shoots of rose ‘Mercedes’ were investigated as a function of the level and spectral quality of the photosynthetically active radiation (PAR). Experiments were performed with single-shoot plants decapitated above the two most basal leaves with five leaflets. The development of the two lateral shoots emerging from the axillary buds of these leaves was studied over a period of 4 to 6 weeks. In order to discriminate between the effects of irradiance level and light quality, plants were grown in growth chambers in which both the amount of PAR and its spectral composition could be controlled. At a photoperiod of 12 h the length, weight, and flowering of the shoots strongly increased with irradiance. Weight and number of flowering shoots were always higher for the uppermost than for the second shoot. At the highest PAR level (270 μmol m-2s-1) flowering occurred in 89 and 33 ␘f the uppermost and second shoots, respectively. At an irradiance level of 90 μmol m-2s-1 these percentages were 6 and 0EAlthough the length of both types of shoots was significantly increased by reducing the amount of blue light at constant PAR, flower development was not affected. In a second experiment plants grown in white light (12 h/day) received a short treatment with low intensity red or far-red light at the end of each photoperiod. An end-of-day treatment with red light resulted in significantly more flowering shoots than far-red. The red/far-red reversibility of this flowering response indicates the involvement of the photoreceptor phytochrome.

Phytochrome Regulation of Photosynthate Partitioning in Watermelon Plants Exposed to End-of-day Light Treatments

End-of-day (EOD) light treatments were used to study phytochrome involvement in photosynthesis and photosynthate partitioning in watermelon plants. Two-week-old plants were treated with brief low-intensity red (R) or far-red (FR) light for 9 days at the end of daily light period. Petiole elongation in the first two leaves was the first significant growth change in FR-treated plants compared to other plants after 3 days of treatments. This petiole elongation was accompanied by significantly higher photosynthate partitioning to petioles, even without increase in above-ground dry weight of plants. Net CO2 assimilation rate in the second leaf was significantly higher in FR treated plants on a weight basis after 3 days of treatments. Far-red-treated plants had lower chlorophyll content per leaf area and higher stem specific weight compared to R-treated plants after 3 and 6 days of treatments, respectively. Transpiration and stomatal conduction were higher in FR-treated plants compared to other treatments after 3 days of treatments. The EOD FR regulated growth and photosynthate partitioning patterns were reversible when FR treated plants were immediately followed by R. This implies EOD R: FR ratio acting through the phytochrome regulates the growth and development processes in watermelon plants.

Lateral shoot formation and flower-bud formation in apple in the first year after budding as affected by air temperature and exposure to red light

Under controlled environment conditions the effect of three air temperatures (16°, 21°, and 26°C) and of low-intensity red light during the night (at 21°C only) on the vegetative development and flower-bud formation of apple trees (cvs Rode Boskoop and Elstar) were evaluated in the first year after budding. Day and night temperatures were the same; soil temperature was 17°C. The vapour pressure deficit of the air was low (about 0.40 kPa at each temperature). Shoot growth increased with increasing temperature especially in the 16-21°C range. The growth effects were mainly reflected in lateral shoot growth. At 16°C lateral growth was poor (in ‘Boskoop’) or almost absent (in ‘Elstar’). At 26°C, lateral shoots was more evenly spread along the main axis than at lower temperatures. Exposure to red light had no effect on growth. Flowering on the main stem and on the lateral shoots were considerably less at higher temperature. The same held when only clusters with more than four well developed flowers were consid...

Diel cycles inHoplosternum littorale (Teleostei): entrainment of feeding activity by low intensity colored light

Low intensity colored light is very often used to observe or manipulate fish during the scotophase. According to data on fish vision, most species can perceive these wavelengths of light since their cone pigments have maximum absorption peaks around 455, 530 and 625 nm. To test whetherHoplosternum littorale can detect low intensity red or blue light, we attempted to entrain feeding activity, known to be nocturnal and synchronized by the circadian light/dark alternation, to such light. Feeding activity was entrained with either red or blue light, indicating that these fish can perceive these lights. In all cases, the fish fed during the darker phase of the light cycle.

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.

Intact Plastids Are Required for Nitrate- and Light-Induced Accumulation of Nitrate Reductase Activity and mRNA in Squash Cotyledons

Induction of nitrate reductase activity and mRNA by nitrate and light is prevented if chloroplasts are destroyed by photooxidation in norflurazon-treated squash (Cucurbita maxima L.) cotyledons. The enzyme activity and mRNA can be induced if norflurazon-treated squash seedlings are kept in low-intensity red light, which minimizes photodamage to the plastids. It is concluded that induction of nitrate reductase activity and nitrate reductase mRNA requires intact plastids. If squash seedlings grown in low-intensity red light are transferred to photooxidative white light, nitrate reductase activity accumulates during the first 12 hours after the shift and declines thereafter. Thus photodamage to the plastids and the disappearance of nitrate reductase activity and mRNA are events separable in time, and disappearance of the enzyme activity is a consequence of the damage to the plastids.

The Effect of Red Light on Reproduction in Peromyscus maniculatus

Pairs of deer mice ( Peromyscus maniculatus ) were exposed to low-intensity red or white light during the active period of their daily cycle for 16 weeks. Analyses of 17 variables, including interlitter interval, percent of pairs breeding, mean litter size, testes mass, and several measures of puberty, indicated that there was no effect of red light on reproduction. However, moving young deer mice from their room of birth influenced gain in mass and growth of testes negatively.

Photomagnetic effects in calcium and germanium substituted yttrium iron garnets (abstract)

Photoinduced changes in the coercivity of uncompensated calcium and germanium substituted yttrium iron garnet epilayers have been observed. The experimental results indicate that there exists a ‘‘critical’’ temperature below which coercivity of the sample increases by up to 20% under illumination of low intensity red light. Around this same temperature range the measured temperature dependence of the magnetization M(T) and anisotropy field display significant anomalies. The theoretical simulations for M(T) curves have been performed by using a molecular field approach. Since the measured temperature dependence of the magnetization of the uncompensated films could not be explained by the usual two sublattice model, a third contribution proportional to the deviation of the magnetization from bulk values was introduced. These results demonstrate the possibility of a weakly bound hole at the Ca site which contributes to the magnetic properties of these materials.

Regulation of calmodulin- and dopamine-stimulated adenylate cyclase activities by light in bovine retina.

Neural retina from most species contains 3,4- dihydroxyphenylethylamine (dopamine) receptors coupled to stimulation of adenylate cyclase activity. It has been demonstrated that release of dopamine from its neurons and subsequent occupation of dopamine receptors is increased by light. In this study, we have shown that adenylate cyclase activity in bovine retina is highly responsive to the endogenous Ca2+-binding protein, calmodulin, and that calmodulin can increase dopamine-sensitive adenylate cyclase activity in bovine retina. We further demonstrate that both dopamine- and calmodulin-stimulated adenylate cyclase activities can be regulated by alterations in light. Bovine retinas were dissected from the eye under a low-intensity red safety light, defined as dark conditions, and incubated for 20 min in an oxygenated Krebs Henseleit buffer under either dark or light conditions. The retinas were then homogenized and adenylate cyclase activity measured in a particulate fraction washed to deplete it of endogenous Ca2+ and calmodulin. Activation of adenylate cyclase activity by calmodulin, dopamine, and the nonhydrolyzable GTP analog, guanosine-5'-(beta,gamma-imido)triphosphate ( GppNHp ), was significantly (60%) greater in particulate fractions from retinas that had been incubated under dark conditions as compared to those incubated under light conditions. Basal, Mn2+-, and GTP-stimulated adenylate cyclase activities were not altered by changes in lighting conditions. Calmodulin could increase the maximum stimulation of adenylate cyclase by dopamine in retinas incubated under either dark or light conditions, but the degree of its effect was greater in retinas incubated under light conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Diversity of abundant mRNA sequences and patterns of protein synthesis in etiolated and greened pea seedlings

The diversity of abundant mRNA sequences in various parts of 4-d etiolated pea seedlings (Pisum sativum L. var. Rondo CB) was compared by a cell-free translation of the mRNAs in the presence of [(35)S]methionine and by an analysis of the products by two-dimensional electrofocussing/ electrophoresis (2D separation). The various parts of the seedlings were also examined for the pattern of protein synthesis in vivo. Proteins were labeled by injection of [(35)S]methionine into the cotyledons, followed by 2D separation of the products. Over 95% of the abundant mRNA sequences and newly synthesized abundant polypeptides were shared by all parts of etiolated seedlings, including the cotyledons. However, a few distinct differences were observed when comparing mRNAs of roots and shoots; the most prominent among these were a group of six abundant mRNA sequences found exclusively in shoots. Only about 30% of the polypeptides synthesized on isolated RNA could be traced in equivalent positions on the gels as the polypeptides synthesized in vivo. Analysis of total RNA from light-grown pea seedlings showed the appearance of some twenty-five translation products not found with total RNA from etiolated seedlings, while about nine other translation products disappeared. At least ten of the light-induced RNA sequences were also present after growth in low-intensity red light (λ>600 nm) and are therefore thought to be controlled by the phytochrome system. Comparison of 11-d light-grown pea plants with 4-d light-grown seedlings did not reveal additional translatable RNA sequences, indicating that the major morphogenetic changes that occur after 4 d are not accompanied by significant changes in the pattern of abundant RNA sequences.

Light scattering, chlorophyll fluorescence and state of the adenylate system in illuminated spinach leaves

Scattering of green light and chlorophyll fluorescence by spinach leaves kept in a stream of air or nitrogen were compared with leaf adenylate levels during illumination with blue, red or far-red light. Energy charge and ATP-ADP ratios exhibited considerable variability in different leaves both in the dark and in the light. Variability is explained by different possible states of the reaction oxidizing triose phosphate or reducing 3-phosphoglycerate. Except when oxygen levels were low, there was an inverse relationship between light scattering and chlorophyll fluorescence during illumination with blue or red light. When CO 2 was added to a stream of CO 2-free air, chlorophyll fluorescence increased, sometimes after a transient decrease, and both light scattering and leaf ATP ADP ratios decreased. Similar observations were made when air was replaced by nitrogen under blue or high-intensity red light. Under these conditions, over-reduction caused inhibition of electron transport and phosphorylation in chloroplasts. However, when air was replaced by nitrogen during illumination with low-intensity red light or far-red light, light scattering increased instead of decreasing. Under these light conditions, ATP ADP ratios were maintained in the light. They decreased drastically only after darkening. Although ATP ADP ratios responded faster than light scattering or the slow secondary decline of chlorophyll fluorescence due to illumination, it appeared that in the steady state, light scattering and chlorophyll fluorescence are useful indicators of the phosphorylation state of the leaf adenylate system at least under aerobic conditions, when chloroplast and extrachloroplast adenylate systems can effectively communicate.