Artificial light-sensitive enzymatic systems as chemical amplifiers of weak light signals.
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Enzyme Activation↗
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Results for “Light signaling”
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Information transfer characteristics of moving light signals.
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Adult↗
The ability of color defectives to judge signal lights at sea.
Measures were made of the ability of color-defective men to judge correctly the colors of navigation lights (red, green, or white) presented to them at night under realistic sea conditions. Eighty-one color-defective men were employed; they were categorized as to type and degree of defect using a battery of five color-vision tests. While the average performance of the color-defective men was considerably poorer than that of 24 color normals, there were large individual differences within each category of defect. Attempts to account for these differences in performance by variations in acuity, intelligence, and motivation failed. The extent to which the data can be accounted for by modern color-vision theory is discussed.
Color Vision Defects↗
Functional changes of the aging rat retina in relation to the modifications of the ERG components.
the intact eye of Wistar rat was stimulated with continual periodic light signals in the range of 0,001-500 lux and from 0,01 cps. up to the fusionfrequency. Using square-wave light stimuli of the frequency range from 0,01 to 0,1 cps. and intensity diapason of 0,1-1,0 lux the scotopic electroretinogram (ERG) consists of the following waves: b, b-negative, c, d, d-positive, respectively. At the beginning of the light sensitivity range, that is near above the threshold, on one part and over a stimulus intensity of 10 lux, on the other the ERG becomes more simple and looks appr. like a direct current (DC) response. Along with aging the ERG undergoes changing. The light sensitivity of the eye proved to be decreased, especially in the short wave range of the spectrum. Thus the ERG threshold becomes increased. The DC components are less apparent. The fast elements of high amplitudes are also missing. The slope of the frontal and descending part of the wave b gets lower. The fusion-frequency is lower with old animals as well. The spontaneous physiological biopotential noise level is significantly higher and the synchronity of elements participating in generating the ERG wave is less. Additionally a considerable great slowing-down of the adaptation processes were observed. Using light signals of different wave forms, it may be established, that differentiating ability of the retina declines more rapidly as aging advances than that of its light sensitivity.
Aging↗
Unraveling the molecular choreography of C3 to CAM transition in Mesembryanthemum crystallinum using phosphoproteomics.
Climate change and population growth threaten global freshwater resources and food security. Crassulacean acid metabolism (CAM) is a specialized photosynthetic adaptation that exhibits superior water use efficiency (WUE) compared to C3 and C4 photosynthesis. Mesembryanthemum crystallinum (common ice plant) is capable of shifting from C3 to CAM, making it a key model for investigating photosynthesis plasticity and its potential to enhance crop stress resilience. To date, the molecular mechanisms underlying this high-WUE photosynthetic transition remain largely unknown. Using mass spectrometry-based proteomics and phosphoproteomics, we quantified 4233 phosphopeptides containing 4758 phosphorylation sites, including the well-characterized Serine 11 of phosphoenolpyruvate carboxylase 1 (PEPC1). It is a critical phosphorylation site facilitating nocturnal CO2 fixation during CAM. Our analysis revealed many phosphorylation sites that exhibited similar diel patterns as the PEPC1 pS11, and they may be part of the regulatory network involved in CAM induction. Glycolysis/gluconeogenesis and carbon storage/breakdown modules exhibited extensive phosphorylation regulation, and vesicle trafficking could play a role in nocturnal carbon fixation. Furthermore, glycine-rich RNA-binding protein 7 (GRP7) in association with cold shock protein 1 (CSP1) emerged as a potential transcriptional switch for nocturnal stomatal opening. On the other hand, ABI5-binding protein 1 (AFP1) and oxidative stress 3 (OXS3)-activated ABA signaling, along with high CO2 signaling and suppressed blue light signaling, may contribute to diurnal stomatal closure. These findings shed light on the protein phosphorylation changes and provide valuable targets for functional characterization of their roles in CAM induction.
Mesembryanthemum↗
Circadian- and light-regulated oscillatory expression of CSA in rice leaves is required for pollen fertility.
The oscillatory expression of CSA in rice leaves is regulated by the circadian clock and red/far-red light signals, mediated through DOF5 and PIL11, and is required for normal pollen fertility. Photoperiod-sensitive male-sterile lines represent a pivotal innovation in the development of hybrid rice. However, the underlying mechanisms governing photoperiod-sensitive male reproductive development remain poorly understood. Our previous studies demonstrated that the carbon starved anther (csa) mutant exhibits male sterility under short-day (SD) conditions but partial fertility under long-day (LD) conditions. In this study, we report that CSA expression follows an oscillatory rhythm in rice leaves under both SD and LD conditions, a pattern regulated by both circadian clock and light signals. Tissue-specific RNA interference knockdown of CSA in leaves was associated with reduced pollen viability, suggesting that CSA expression in leaves contributes to normal male fertility. Promoter truncation assay results indicate that distinct regions of the CSA promoter contribute differentially to the regulation of CSA expression in leaves versus anthers, and that both the CSA expression level in anthers and the rhythmic expression pattern of CSA in leaves are associated with the restoration of male fertility. Using dual-luciferase, yeast one-hybrid, and electrophoretic mobility shift assays, we identified two proteins, PIL11 and DOF5, which directly bind to specific motifs (an E-box and T/AAAAG motif) within the CSA promoter truncation, thereby regulating its transcription. These findings elucidate novel mechanisms linking light sensing to the expression of circadian-controlled genes, thus connecting photoperiod with male reproductive development in rice.
Oryza↗
A PIF-regulated switch in cell axis growth drives cotyledon expansion through tissue-specific cell expansion and division.
Despite its crucial role during seedling deetiolation, cotyledon expansion has been largely overlooked, with hypocotyl elongation favored as the primary phenotypic readout in light signaling research. Here, we investigate how cotyledon expansion is regulated during seedling establishment and reveal that light-induced cotyledon expansion involves a rapid switch in growth direction - from longitudinal in darkness to transversal upon initial light exposure. Using PIFq- and phyA/phyB-deficient Arabidopsis mutants, we demonstrate that this switch is repressed by PIFs in the dark and promoted by phytochromes under red light. Notably, expansion is antagonistically regulated in the light by GUN1-mediated plastid retrograde signaling. Cotyledon expansion involves rapid epidermis cell expansion, transitioning from rectangular in darkness to characteristic lobed cells in light. Importantly, our findings show that mesophyll extension is driven not only by cell enlargement but also by palisade cell division, consistent with an enrichment of cell cycle-related genes that are antagonistically regulated by the PIF/phy system and retrograde signaling in the cotyledon. Finally, using mutant lines expressing PIF1 and phyB specifically in the epidermis, we establish that epidermal expansion can drive palisade cell growth, while mesophyll cell division is predominantly regulated by light at the tissue-specific level. This study provides a novel framework for investigating cotyledon expansion during seedling deetiolation, incorporating tissue-level regulation. We propose that cotyledons serve as an excellent model for studying morphogenesis and organ geometry, which in plants is governed by directional cell growth.
Cotyledon↗
Estimation of time intervals--elements of an array of three intervals.
The article reports the results of experiments on human ability to estimate time intervals separately or in groups of two intervals as elements of a three-interval array presented by two light signals separated by a dark interval. The first light interval is shown to be systematically overestimated compared with the second one. Moreover, the subjects usually ascribe a constant value to the dark interval. The double interval (light + dark or dark + light) proves to be underestimated compared with the case when estimation of the same intervals was required without estimation of a third interval. The additional task changes the estimations of the subjects. It may be claimed that the complexity of the problem is connected with definite changes in the average estimations of the subjects.
Darkness↗
The current status of auotomobile running lights.
The results of a number of studies of the use of lights to make a vehicle more visible have shown that they are effective. Accident studies have shown a drop in accidents from 7 to 59%. Only one of the studies used properly designed and positioned presence and signal lights and yielded 59% fewer accidents. It is concluded that a 50% or greater reduction of accidents is probable when using a high mounted 360 degrees visibility signal and running light combination.
Accidents, Traffic↗
Genome-wide characterization of the sugar transporter protein family identifies candidate genes for bacterial wilt resistance breeding in tobacco.
Sugar transporter proteins (STPs) play pivotal roles in hexose allocation and plant stress responses. However, systematic characterization of the STP family in tobacco (Nicotiana tabacum) and its involvement in Ralstonia solanacearum resistance remains unclear. In this study, 37 NtSTP genes were identified and classified into six groups, with Group VI being the most conserved and Group V exhibiting dicot-specific expansion. Gene structure and conserved motif analyses revealed that most NtSTP members possess the typical MFS_STP domain, although variations in exon-intron organization and motif composition suggested functional divergence. Tandem duplication (TD) served as the primary driver of NtSTP family expansion, and Ka/Ks values of all paralogous pairs were less than 1, indicative of purifying selection. Promoter cis-element analysis revealed a complex regulatory network involving hormone signaling (ABA, JA, SA, GA, ET), stress responses, and light signaling. RT-qPCR expression profiling revealed that ten NtSTP genes (NtSTP1, 5, 7, 21, 22, 24, 26, 27, 28, and 29) exhibited significant transcriptional upregulation upon R. solanacearum infection. Specifically, NtSTP5, NtSTP7, NtSTP21, NtSTP22, NtSTP24, NtSTP26, and NtSTP27 peaked at 12 h post-inoculation (hpi), whereas NtSTP1, NtSTP28, and NtSTP29 reached their highest expression levels at 24 hpi. By contrast, NtSTP6, NtSTP13, and NtSTP30 displayed reduced expression upon R. solanacearum infection. These expression patterns indicate functional diversification within the NtSTP family and imply that these members may be transcriptionally modulated during plant responses to R. solanacearum. The present work provides preliminary and valuable candidate gene resources that may facilitate future disease resistance breeding programs in tobacco.
NtSTP gene family↗
Calcium transients and relaxation in single muscle fibers.
Muscle contraction is initiated by an elevation in intracellular calcium. The transient change in free calcium to a brief depolarization, the calcium transient, can be recorded using a calcium luminescent protein, aequorin. The calcium transient precedes force, peaking while force is rising and returning to the resting level as peak force is achieved. In single barnacle muscle fibers microinjected with aequorin, shortening the muscle during the declining phase of the calcium transient produces an addition light signal, indicating extra free calcium in the sarcoplasm. The amount of additional light is larger with larger length changes. It is also larger if the shortening occurs early in the calcium transient rather than later. The amount of this extra calcium correlates well with the instantaneous level of the calcium transient and not with the instantaneous force level. It is argued in a speculative manner that this extra calcium is coming from the myofilaments. This supports the hypothesis that calcium binding to the myofilaments is rapid and reversible, that reaccumulation of calcium into the sarcoplasmic reticulum (SR) could occur long before relaxation begins and that relaxation of tension could occur by some process other than the mere removal of calcium from the myofilaments.
Aequorin↗
Mechanistic analysis of rice caryopsis morphogenesis regulated by exogenous hormones and related precursor substances under blue light conditions.
Rice caryopsis morphogenesis is regulated by light signals and hormonal networks. However, the mechanism by which exogenous hormones and related precursor substances modulate rice caryopsis morphogenesis under blue light remains elusive. In the present study, we aimed to elucidate the molecular mechanisms underlying the regulatory effects of exogenous phytohormones and related precursor substances on caryopsis development at 10 days after pollination (10 DAP) in the japonica rice cultivar 'Chujing 27' under blue light conditions. Results showed that tryptamine treatment increased caryopsis cell volume, thereby significantly driving caryopsis expansion; meanwhile, it markedly enhanced the activities of TDC and TAA, the key rate-limiting enzymes mediating the conversion of tryptophan to auxin, leading to a significant elevation in endogenous auxin content (P < 0.05). In comparison, exogenous auxin treatment significantly boosted carbohydrate accumulation and the activities of associated metabolic enzymes (P < 0.05). Integrated transcriptomic and metabolomic analyses revealed that tryptamine treatment led to significant enrichment of the starch and sucrose metabolic pathway, and drove the coordinated enhancement of carbon metabolic flux and auxin biosynthesis by upregulating key auxin biosynthetic genes (e.g., TAA1) and repressing auxin oxidative degradation. Genes Os04g0531100, Os03g0266100 and Os11g0221200 identified by weighted gene co-expression network analysis (WGCNA) may serve as important candidate targets regulating rice caryopsis morphology and physiological traits under blue light conditions. This study first uncovers the critical function of the "tryptamine-auxin axis" in regulating rice caryopsis development under blue light, laying a theoretical foundation for regulating caryopsis morphogenesis via exogenous hormones and their precursors.
Oryza↗
An improved method of light-induced pigmentation.
An improved procedure was developed whereby a primary light signal can be intensified and made visible by activation of a pre-tyrosinase (pre-phenoloxidase) enzyme [isolated from silkworm (Bombyx mori)] by alpha-chymotrypsin; this activation results from the light-activated conversion of the inactive cis-cinnamoyl-alpha-chymotrypsin.
Animals↗
Long-day photoperiod promotes growth of pea (Pisum sativum L.) via auxin biosynthesis and polar transport.
Photoperiodic sensitivity is an essential factor that may affect agricultural practices under current climate scenarios. This study used pea (Pisum sativum) to examine effects of varying photoperiods on growth and photosynthetic parameters and then reveal the mechanistic basis of this process by linking them with tissue-specific distribution of auxin and regulation of related genes. This was achieved by transcriptome sequencing, genome-wide gene family identification, and expression pattern analysis. Best results in terms of growth and yield were obtained with a 20 h/4 h light/dark photoperiod and these plants had the highest content of endogenous indole-3-acetic acid (IAA) in both the shoot apex and the root. Genes consistently upregulated with prolonged light exposure were significantly enriched in pathways related to light signal transduction, photosynthetic carbon metabolism, and phytohormone signal transduction. Through genome-wide identification, we characterized the TAA/TAR and YUCCA families (key gene families involved in auxin biosynthesis) as well as the PIN family (responsible for auxin polar transport) in pea. Extending the light duration positively affected expression of several genes related to auxin biosynthesis and transport, among them members of the Elongated Hypocotyl (HY) and Phytochrome-Interacting Factor (PIF) families being key light-induced transcription factors, PsTAR2, the principal gene regulating auxin biosynthesis, as well as PsPIN4, PsPIN5, PsPIN11, and PsPIN13 which mediate polar auxin transport. By elucidating mechanisms underlying the coordinated regulation of pea growth by light and auxin, this work provides a significant reference for photoperiod research on long-day crops for both protected- and field-based horticulture.
Auxin↗
Light regulates capsaicinoid biosynthesis via the CaHY5-CaBBX2-CaACS8 module in pepper.
Capsaicinoids are a class of unique alkaloids that confer the pungent taste to pepper fruits. However, it remains largely unknown how light regulates the biosynthesis of capsaicinoids. We conducted a metabolic analysis on light- and dark-adapted pepper fruits. The results showed that dark-adapted pepper fruits had lower capsaicinoid contents and correspondingly downregulated transcription of capsaicinoid biosynthetic genes (CBGs), indicating that light plays a crucial role in capsaicinoid biosynthesis. Furthermore, silencing of CaHY5, a pivotal transcription factor gene in the light signaling pathway, decreased the content of capsaicinoid and suppressed the expression of CBGs, whereas transient overexpression of CaHY5 generated exactly opposite results. CaHY5 can bind to the G-box motif in the promoters of CaBBX2 and CaACS8, thereby enhancing their transcriptional levels. The activated CaBBX2 then binds to the T/G-box in the CaACS8 promoter to stimulate its expression. CaBBX2 or CaACS8 silencing led to decreased levels of capsaicinoids, while their transient overexpression produced increased capsaicinoid contents. Collectively, our results indicated that the light-activated CaHY5-CaBBX2-CaACS8 regulatory module plays a pivotal role in capsaicinoid biosynthesis. These findings provide new insights into the influence of light on capsaicinoid biosynthesis and potential targets for activation of this biosynthetic pathway in pepper.
Capsicum↗
Light-induced enzyme system leading to pigmentation.
Alpha-Chymotrypsin was light sensitized by acylating with cis-cinnamoyl ester, a substrate interconvertible to the trans form by ultraviolet (UV) light. The degree of acylation by this method was complete leaving no residual activity of the enzyme. Upon UV irradiation the inhibited enzyme regained about 70% of its original activity, thereby adding light-sensitiveness to the proteolytic enzyme. In seeking a photographic application of the light-sensitized enzyme, a pigmenting enzyme was incorporated with it. The coupled enzyme system was shown to exhibit a light signal in the form of dark pigment slurry.
Catechol Oxidase↗
MSH/ACTH4-10 influences on the CAR in human subjects: a negative finding.
Twenty normal, male, paid volunteers were randomly assigned to MSH/ACTH4-10 or diluent control groups. Following a subcutaneous injection of either 30 mg MSH/ACTH4-10 or diluent, all subjects were placed in an active conditioned avoidance response situation where they learned to avoid a painful electric shock by pressing a key during a safe interval between a warning signal (light) and shock onset. MSH/ACTH4-10 did not influence any parameter of the acquisition or extinction process. The between subjects' variability of autonomic variables was significantly less for the MSH/ACTH4-10 group. Results indicate that inhibition of extinction of conditioned avoidance responding does not generalize across species from rat to man.
Adrenocorticotropic Hormone↗
Depth of nontarget processing in an attention task.
Two studies examined the effect of the sensory discriminability of targets from nontargets on depth of nontarget processing. Subjects shadowed target words that were binaurally presented with coincident nontarget words. Targets and nontargets were spoken in the same male voice under low sensory discriminability and in male and female voices, respectively under high sensory discriminability. Across the two studies, depth of nontarget processing was assessed in three ways: extent to which shadowing accuracy was disrupted by a semantic overlap between targets and nontargets, expenditure of capacity (reaction time to subsidiary light signals), and nontarget recall. All three possible measures of depth of nontarget processing decreased as sensory discriminability increased. The data support the assumption of multiple-loci theories of attention that nontargets can be perceptually inhibited; they contraindicate the assumption of late-selection theories that perceptual processing is automatic and irrepressible.
Attention↗