Low Light Exposure Research Articles

A Denoise Network for Structured Illumination Microscopy with Low-Light Exposure

Super-resolution structured illumination microscopy (SR-SIM) is one of the important techniques that are most suitable for live-cell imaging. The reconstructed SR-SIM images are noisy once the raw images are recorded with low-light exposure. Here, we propose a new network (entitled the ND-SIM network) to denoise the SR images reconstructed using frequency-domain algorithms (FDAs). We demonstrate that ND-SIM can yield artifact-free SR images using raw images with an average photon count down to 20 per pixel while achieving comparable resolution to the ground truth (GT) obtained with high-light exposure. We can envisage that the ND-SIM will be widely applied for the long-term, super-resolution live-cell imaging of various bioprocesses in the future.

A universal self-delivery lactate metabolism regulating polyprodrug enhances tumor photodynamic therapy

Lactate plays vital roles in promoting immunosuppressive tumor microenvironment, tumor angiogenesis and drug resistance, therefore, lactate modulation is a promising strategy to conquer the restrictions of many therapeutic modalities. A universal drug self-delivery nano-platform with easy synthesis and superior biosafety for lactate regulation is still needed. Herein, α-cyano-4-hydroxycinnamic acids (α-CHC), as monocarboxylic acid transporter 1 (MCT1) inhibitors, are polycondensed into poly (α-cyano-4-hydroxycinnamic acid) (PCHC) for the first time to function as both the lactate metabolism regulation prodrug and a drug carrier of, in this case, photosensitizer Protoporphyrin IX (PpIX). Once triggering by the intracellular esterase, the co-assembled PCHC@PpIX nanoparticles (shorted as PCPp NPs) are degraded accordingly and the generated α-CHC monomer inhibits MCT1 to cut down the lactate influx and further reduces endogenous oxygen (O2) loss in tumor cells. By utilizing the elevated O2 level, the released PpIX produces more cytotoxic reactive oxygen species (ROS) and only a single dosage (total PpIX: 0.10 mg per mice) with extremely low light exposure (3.5 J cm-2) is needed for tumor elimination. This work provides a charming lactate metabolic modulating polyprodrug based self-delivery nano-platform for universal hydrophobic drug delivery to improve anticancer efficacy especially for those oxygen dependent therapeutic strategies.

Sleep patterns in Metropolitan and Regional areas in Japan: Before and during COVID-19 social restrictions

ABSTRACT Sleep timing is an important output of the circadian system. The COVID-19-mandated social restrictions significantly altered commuting time and sleep duration regionally in Japan. This study aimed to elucidate sleep patterns, especially chronotype and social jetlag (SJL), due to changes in social time pressure through the social restrictions between the Metropolitan and Regional areas in Japan. As part of the Global Chrono Corona Survey 2020 (GCCS), the data were collected during social restrictions (SR), but pre-COVID-19 behaviours were also queried retrospectively. We analyzed a cohort of 729 respondents representing both the Metropolitan and the Regional areas separately for workdays and work-free days. While the areas showed no difference in SJL before SR, the differential decrease was larger in the Metropolitan area during SR, resulting in a significant difference in SJL between the areas. The outdoor light exposure before SR was 30 min longer in the Metropolitan areas than in the Regional; during SR both areas showed similarly low (below 1 h) outdoor light exposures. The variables associated with decreased SJL were the Metropolitan areas, work-from-home, a no-usage alarm clock on workdays, and chronotypes (mid-sleep time on free days corrected for sleep deficit accumulated over the workweek, MSFsc) during SR. The results suggest that relaxed social schedules, as reflected in the increased frequency of work-from-home and reduced alarm clock use, and moving towards earlier MSFsc during SR were linked to decreased SJL and were more prominent in the Metropolitan areas. This study provides insights into sleep patterns and the social time pressure markers, by comparison between residential groups in Japan.

Observing ER Dynamics over Long Timescales Using Light Sheet Fluorescence Microscopy.

The recent significant progress in developmental bio-imaging of live multicellular organisms has been greatly facilitated by the development of light sheet fluorescence microscopy (LSFM). Both commercial and custom LSFM systems offer the best means for long-term rapid data collection over a wide field of view at single-cell resolution. This is thanks to the low light exposure required for imaging and consequent limited photodamage to the biological sample, and the development of custom holders and mounting techniques that allow for specimens to be imaged in near-normal physiological conditions. This method has been successfully applied to plant cell biology and is currently seen as one of the most efficient techniques for 3D time-lapse imaging for quantitative studies. LSFM allows one to capture and quantify dynamic processes across various levels, from plant subcellular compartments to whole cells, tissues, and entire plant organs. Here we present a method to carry out LSFM on Arabidopsis leaves expressing fluorescent markers targeted to the ER. We will focus on a protocol to mount the sample, test the phototoxicity of the LSFM system, set up a LSFM experiment, and monitor the dynamics of the ER during heat shock.

Evening prolonged relatively low melanopic equivalent daylight illuminance light exposure increases arousal before and during sleep without altering sleep structure

SummaryLight can influence many psychophysiological functions beyond vision, including alertness, circadian rhythm, and sleep, namely the non‐image forming (NIF) effects of light. Melanopic equivalent daylight illuminance (mel‐EDI) is currently recommended as the predictor of the NIF effects of light. Although light dose is also critical for entraining and regulating circadian cycle, it is still unknown whether relatively low mel‐EDI light exposure for prolonged duration in the evening would affect pre‐sleep arousal and subsequent sleep. In all, 18 healthy college students (10 females, mean [standard deviation] age 21.67 [2.03] years) underwent 2 experimental nights with a 1 week interval in a simulated bedroom environment. During experimental nights, participants were either exposed to high or low mel‐EDI light (73 versus 38 lx mel‐EDI, 90 versus 87 photopic lx at eye level, 150 photopic lx at table level) for 3.5 h before regular bedtime, and their sleep was monitored by polysomnography. Subjective sleepiness, mood, and resting‐state electroencephalography during light exposure were also investigated. Results showed no significant differences in sleep structure and sleep quality between the two light conditions, whereas 3.5 h of exposure to high versus low mel‐EDI light induced marginally higher physiological arousal in terms of a lower delta but higher beta power density before sleep, as well as a lower delta power density during sleep. Moreover, participants felt happier before sleep under exposure to high versus low mel‐EDI light. These findings together with the current literature suggest that evening prolonged relatively low mel‐EDI light exposure may mildly increase arousal before and during sleep but affected sleep structure less.

Thioflavin T indicates mitochondrial membrane potential in mammalian cells

The fluorescent benzothiazole dye thioflavin T (ThT) is widely used as a marker for protein aggregates, most commonly in the context of neurodegenerative disease research and diagnosis. Recently, this same dye was shown to indicate membrane potential in bacteria due to its cationic nature. This finding prompted a question whether ThT fluorescence is linked to the membrane potential in mammalian cells, which would be important for appropriate utilization of ThT in research and diagnosis. Here, we show that ThT localizes into the mitochondria of HeLa cells in a membrane-potential-dependent manner. Specifically, ThT colocalized in cells with the mitochondrial membrane potential indicator tetramethylrhodamine methyl ester (TMRM) and gave similar temporal responses as TMRM to treatment with a protonophore, carbonyl cyanide-4-(trifluoromethoxy) phenylhydrazone (FCCP). Additionally, we found that presence of ThT together with exposure to blue light (λ = 405 nm), but neither factor alone, caused depolarization of mitochondrial membrane potential. This additive effect of the concentration and blue light was recapitulated by a mathematical model implementing the potential-dependent distribution of ThT and its effect on mitochondrial membrane potential through photosensitization. These results show that ThT can act as a mitochondrial membrane potential indicator in mammalian cells, when used at low concentrations and with low blue light exposure. However, it causes dissipation of the mitochondrial membrane potential depending additively on its concentrations and blue light exposure. This conclusion motivates a re-evaluation of ThT’s use at micromolar range in live-cell analyses and indicates that this dye can enable future studies on the potential connections between mitochondrial membrane potential dynamics and protein aggregation.

Biocompatibility Evaluation of TiO2, Fe3O4, and TiO2/Fe3O4 Nanomaterials: Insights into Potential Toxic Effects in Erythrocytes and HepG2 Cells.

Nanomaterials such as titanium dioxide and magnetite are increasingly used in several fields, such as water remediation and agriculture. However, this has raised environmental concerns due to potential exposure to organisms like humans. Nanomaterials can cause adverse interactions depending on physicochemical characteristics, like size, morphology, and composition, when interacting with living beings. To ensure safe use and prevent the risk of exposure to nanomaterials, their biocompatibility must be assessed. In vitro cell cultures are beneficial for assessing nanomaterial-cell interactions due to their easy handling. The present study evaluated the biocompatibility of TiO2, Fe3O4, and TiO2/Fe3O4 nanomaterials thermally treated at 350 °C and 450 °C in erythrocytes and HepG2 cells. According to the hemolysis experiments, non-thermally treated NMs are toxic (>5% hemolysis), but their thermally treated counterparts do not present toxicity (<2%). This behavior indicates that the toxicity derives from some precursor (solvent or surfactant) used in the synthesis of the nanomaterials. All the thermally treated nanomaterials did not show hemolytic activity under different conditions, such as low-light exposure or the absence of blood plasma proteins. In contrast, non-thermally treated nanomaterials showed a high hemolytic behavior, which was reduced after the purification (washing and thermal treatment) of nanomaterials, indicating the presence of surfactant residue used during synthesis. An MTS cell viability assay shows that calcined nanomaterials do not reduce cell viability (>11%) during 24 h of exposure. On the other hand, a lactate dehydrogenase leakage assay resulted in a higher variability, indicating that several nanomaterials did not cause an increase in cell death as compared to the control. However, a holotomographic microscopy analysis reveals a high accumulation of nanomaterials in the cell structure at a low concentration (10 µg mL-1), altering cell morphology, which could lead to cell membrane damage and cell viability reduction.

O080 The Associations Between Sleep Environment Factors and Sleep Health in Individuals Living with Neurological Conditions

Abstract Introduction Accumulating evidence indicates that sleep health is worse in individuals living with a neurological condition and may hasten neurodegeneration. The extent to which the sleeping environment, particularly air temperature and light, influence sleep health has not been investigated in individuals living with a neurological condition. This research aimed to explore, for the first time, associations between air temperature and light in the sleeping environment and sleep health in individuals living with a neurological condition. Methods The sleep health, including the domains of sleep quality, duration, and disorders, of 46 individuals with a neurological condition was measured using the Sleep Health Index. Air temperature and light data were captured across seven days using a light/temperature data logger positioned next to the participant's bed. Data recorded during the participants' sleeping periods (determined using a sleep diary) were analysed. Linear regression models were used to assess the associations between air temperature and light and sleep health (including domains). Results This study showed that for every additional minute of low (10 to 50 lux) light exposure during sleep periods, sleep quality decreased by 9%. Discussion Our findings suggest that low light exposure during sleep periods may be detrimental to the sleep quality of individuals with neurological conditions.

Morphological and transcriptomic responses/acclimations of erect-type submerged macrophyte Hydrilla verticillata both at low-light exposure and light recovery phases.

Light intensity is a determinant for submerged macrophytes. Little is known about their molecular responses to low-light exposure, despite more informative and responsive than morphological traits. For erect-type submerged macrophytes, the stem is more crucial relative to the leaf in acclimation to low-light stress, but receives less attention. We determined morphological and stem transcriptomic responses/acclimations of Hydrilla verticillata to extremely and mildly low light (7.2 and 36 μmol photons m-2 s-1, respectively), that is, EL and ML, with the radiation intensity of 180 μmol photons m-2 s-1 as the control. Low-light exposure continued for 9 days, followed by a 7-day recovery phase (180 μmol photons m-2 s-1). At the exposure phase, the low-light treatments, in particular the EL, decreased the relative growth ratio, but induced greater height and longer stem internode distance and epidermal cell. Such responses/acclimations continued into the recovery phase, despite more or less changes in the magnitude. Transcriptome showed that the photosynthetic system was inhibited at the exposure phase, but the macrophyte adjusted hormone synthesis relating to cell division and elongation. Moreover, the EL activated cell stress responses such as DNA repair. Following light recovery, the macrophyte exhibited a strong-light response, although energy metabolism enhanced. Especially, the EL enriched the pathways relating to anthocyanin synthesis at such phase, indicating an activation of photoprotective mechanism. Our findings suggest that negative influences of low light occur at both low-light exposure and recovery phases, but submerged macrophytes would acclimate to light environments. Transcriptome can show molecular basis of plant responses/acclimations, including but not limited to morphology. This study establishes a bridge connecting morphological and molecular responses/acclimations.

A comparative analysis of gene and protein expression in chronic and acute models of photoreceptor degeneration in adult zebrafish.

Background: Adult zebrafish are capable of photoreceptor (PR) regeneration following acute phototoxic lesion (AL). We developed a chronic low light (CLL) exposure model that more accurately reflects chronic PR degeneration observed in many human retinal diseases. Methods: Here, we characterize the morphological and transcriptomic changes associated with acute and chronic models of PR degeneration at 8 time-points over a 28-day window using immunohistochemistry and 3'mRNA-seq. Results: We first observed a differential sensitivity of rod and cone PRs to CLL. Next, we found no evidence for Müller glia (MG) gliosis or regenerative cell-cycle re-entry in the CLL model, which is in contrast to the robust gliosis and proliferative response from resident MG in the AL model. Differential responses of microglia between the models was also observed. Transcriptomic comparisons between the models revealed gene-specific networks of PR regeneration and degeneration, including genes that are activated under conditions of chronic PR stress. Finally, we showed that CLL is at least partially reversible, allowing for rod and cone outer segment outgrowth and replacement of rod cell nuclei via an apparent upregulation of the existing rod neurogenesis mechanism. Discussion: Collectively, these data provide a direct comparison of the morphological and transcriptomic PR degeneration and regeneration models in zebrafish.

Fluorescence microscopy images denoising via deep convolutional sparse coding

Fluorescence microscopy images captured in low light and short exposure time conditions are always contaminated by photons and readout noises, which reduce the fluorescence microscopy images quality. In most cases, this kind of noise can be modeled as Poisson–Gaussian noise. Correspondingly, its denoising task has always been a hot but challenging topic in recent years. In this paper, by integrating model-driven and learning-driven methodologies, we propose an end-to-end supervised neural network for fluorescence microscopy images denoising, named MCSC-net, which embeds the multi-layer learned iterative soft threshold algorithm (ML-LISTA) into deep convolutional neural network (DCNN). Our approach not only uses the strong learning ability of DCNN to adaptively update all parameters in the ML-LISTA, but also introduces dilated convolution into network training without additional parameters to improve denoising performance. In addition, compared with several related methods on a real data set of fluorescence microscopy images, MCSC-net achieves the best denoising effects both in qualitative and quantitative aspects, which shows its strong appeal in practical denoising applications.

Marine heatwave and reduced light scenarios cause species-specific metabolomic changes in seagrasses under ocean warming.

Climate change and extreme climatic events, such as marine heatwaves (MHWs), are threatening seagrass ecosystems. Metabolomics can be used to gain insight into early stress responses in seagrasses and help to develop targeted management and conservation measures. We used metabolomics to understand the temporal and mechanistic response of leaf metabolism in seagrasses to climate change. Two species, temperate Posidonia australis and tropical Halodule uninervis, were exposed to a combination of future warming, simulated MHW with subsequent recovery period, and light deprivation in a mesocosm experiment. The leaf metabolome of P. australis was altered under MHW exposure at ambient light while H. uninervis was unaffected. Light deprivation impacted both seagrasses, with combined effects of heat and low light causing greater alterations in leaf metabolism. There was no MHW recovery in P. australis. Conversely, the heat-resistant leaf metabolome of H. uninervis showed recovery of sugars and intermediates of the tricarboxylic acid cycle under combined heat and low light exposure, suggesting adaptive strategies to long-term light deprivation. Overall, this research highlights how metabolomics can be used to study the metabolic pathways of seagrasses, identifies early indicators of environmental stress and analyses the effects of environmental factors on plant metabolism and health.

0307 Day and night light exposure are associated with psychiatric disorders: An objective light study in &amp;gt;80,000 people

Abstract Introduction Circadian rhythm disturbance is a common feature of many psychiatric disorders. Light is the primary input to the circadian clock, with daytime light strengthening rhythms and night light disrupting them. Therefore, habitual light exposure may represent an environmental risk factor for susceptibility to psychiatric disorders. Methods We performed the largest to-date cross-sectional analysis of light, sleep, physical activity, and mental health in participants from the UK Biobank actigraphy cohort (n = 86,772 adults; aged 62.4 ± 7.4 years; 57% women). We examined the independent association of day and night light exposure intensity with covariate-adjusted risk for psychiatric disorders and self-harm. Results Greater night light exposure was associated with increased risk for major depressive disorder, generalized anxiety disorder, PTSD, psychosis, bipolar disorder, and self-harm. Independent of night light, greater day light exposure was associated with reduced risk for major depressive disorder, PTSD, psychosis, and self-harm. These findings were robust to adjustment for sociodemographics, photoperiod, physical activity, and sleep quality. Conclusion Our findings demonstrate that low day light and bright night light exposure are associated with a wide range of psychiatric outcomes. Avoiding light at night and seeking light during the day may be a simple and effective, non-pharmacological means of broadly improving mental health. Support (if any)

0310 Low light exposure during wake is associated with antepartum depressive symptoms

Abstract Introduction Antepartum depression affects 7-16% of pregnant women and occurs most frequently in the 3rd trimester. Previous studies have demonstrated a relationship between the level and timing of daytime light exposure and depression in non-pregnant populations. However, much less is known about the relationships between light exposure and depression during pregnancy. Thus, in this study, we tested the hypothesis that exposure to less daytime light will be associated with more antepartum depressive symptoms. Methods Data from the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-be (nuMoM2b) and the nuMoM2b Sleep Duration and Continuity Substudy were used (N=708). Women enrolled in the substudy wore wrist actigraphy (Spectrum, Phillips Respironics) and completed a sleep log for seven days between 160-230 weeks of gestation. Daytime light exposure was defined as minutes spent at or above the threshold of 50 lux (TAT50) during the wake period, averaged over valid actigraphy recording days. Participants were divided into two groups by TAT50: &amp;gt;25th percentile and ≤25th percentile. The Edinburgh Postnatal Depression Scale (EPDS) was administered during the 1st and 3rd trimesters. A positive screening was defined as an EPDS composite score ≥10 or any endorsement of self-injurious thoughts. Wilcoxon rank sum tests were used to test differences between TAT50 groups. Results Low light exposure during the day was associated with antepartum depressive symptoms during the 1st and 3rd trimesters, after adjusting for age, season, race, poverty, sleep midpoint, and sleep duration (OR 1.7, p=0.047). Additionally, later sleep timing, greater day-to-day sleep variability, and increased time spent awake after sleep onset was seen in those exposed to less light (all p&amp;lt; 0.001). Conclusion Lower daytime light exposure is associated with poorer sleep quality and may increase risk for antepartum depressive symptoms. These data suggest that in addition to improving sleep quality, promoting daytime light exposure may be a modifiable risk factor for depression during pregnancy. Support (if any) Work supported by NHLBI grant R01 HL105549 and NICHD grant U10 HD063036. C.D.W. was funded, in part, by T32HL007909. K.J.R., and P.C.Z. are supported, in part, by R01 HL140580 and P01 AG011412. M.K. is supported, in part, by NIA P30AG059988.

Low energy multiple blue light-emitting diode light Irradiation promotes melanin synthesis and induces DNA damage in B16F10 melanoma cells.

Visible light is present everywhere in our lives. Widespread use of computers and smartphones has increased the daily time spent in front of screens. What effect does this visible light have on us? Recent studies have shown that short-wavelength blue light (400-450nm) irradiation, similar to UV, inhibits the cell proliferation and differentiation, induces the intracellular oxidative stress, promotes the cell apoptosis and causes some other negative effects. However, it's unusual that directly face to such short-wavelength and high-energy blue light in daily life. Therefore, the effects of blue light with longer wavelength (470nm), lower energy (1, 2 J/cm2) and multiple times (simulated daily use) exposure on cells have been studied in this experiment. In our results, low energy density multiple blue light inhibited cell proliferation and metastatic capability with a weak phototoxicity. Blue light also promoted intracellular reactive oxygen species and caused DNA damage. Furthermore, the melanin synthesis was also promoted by low energy density multiple blue light exposure. Together, these results indicate that longer wavelength and low energy density blue light multiple exposure is still harmful to our cells. Furthermore, prolonged exposure to screens likely induces dull skin through induction of melanin synthesis. These results further mentioned us should paid more attention to controlling the daily use of digital device.

Preliminary evidence that daily light exposure enhances the antibody response to influenza vaccination in patients with dementia

Enhancing lighting conditions in institutions for individuals with dementia improves their sleep, circadian rhythms and well-being. Here, we report first findings that exposure to brighter light during daytime may support the immune response to the annual influenza vaccination. Eighty older institutionalised patients suffering from dementia (54 women and 26 men) continuously wore an activity tracker for 8 weeks to assess individual light exposure and rest-activity cycles. We analysed the patients’ immune response from two blood samples taken before and 4 weeks after the annual influenza vaccination. Individual antibody concentrations to three influenza virus strains (H3N2, H1N1, IB) were quantified via hemagglutination inhibition assays. By quantifying individual light exposure profiles (including daylight), we classified the patients into a low and a high light exposure group based on a median illuminance of 392.6 lux. The two light exposure groups did not differ in cognitive impairment severity, age or gender distribution. However, patients in the high light exposure group showed a significantly greater circadian rest-activity amplitude (i.e., more daytime activity and less nighttime activity) along with a significantly greater antibody titer increase to the H3N2 vaccine than patients in the low light exposure group, despite similar pre-vaccination concentrations. Sufficient seroprotective responses to all three influenza virus strains were attained for ≥75% of participants. These data provide preliminary evidence for a potentially enhanced immune response in patients with dementia when they received more daily light. Future studies are needed to determine whether regular daily light exposure may have beneficial effects on the human immune system, either directly or via a stabilising circadian sleep-wake rhythms.

Global diversity and adaptations of avian eggshell thickness indices

The amniote eggshell is a fundamental aspect of the embryo life‐support system, protecting it from UV light, microbes and mechanical damage, while regulating gas exchange and providing calcium for growth. The thickness of eggshells is highly diverse across modern birds and influences multiple eggshell functions, yet the selective pressures driving eggshell thickness have not been clearly identified. Here, we use a global dataset of avian eggshell thickness indices for 4260 (&gt; 41%) avian species to assess trends in eggshell thickness across the phylogeny, as these indices are strongly correlated with direct measures of eggshell thickness and are non‐destructive to the sample. We analysed the dataset within a phylogenetic framework to assess the relative importance of climatic and ecological explanations for variation in eggshell thickness indices. The distribution of avian eggshell thickness indices across species was found to be primarily driven by phylogenetic relatedness, in addition to evolutionary processes that do not match a Brownian model of evolution. Across modern birds, thicker eggshells were more prevalent in species (1) with precocial young, (2) which exhibit a scavenger‐based diet, (3) which primarily feed on vertebrates or plants (excluding nectivores, seed and fruit specialists) and (4) which breed in open habitats. Thicker eggshells found in species with precocial young probably enable higher rates of calcium removal for the more advanced embryo development. Excessive light transmission through the shell damages developing embryos, while too little light transmission can impede development. Eggs in shaded habitats experience low light exposure, and thus thinner shells are more prevalent in these environments potentially to increase light transmission through the shell. Overall, variation in eggshell thickness indices appears to be driven largely by phylogeny, with certain life‐history traits linked to embryo growth rate, calcium content of their food, and the need to mitigate excessive light transmission through the shell.

Microneedles loaded with glutathione-scavenging composites for nitric oxide enhanced photodynamic therapy of melanoma.

Photodynamic therapy (PDT) represents an attractive promising route for melanoma treatment. However, its therapeutic efficacy is compromised by inefficient drug delivery and high glutathione (GSH) levels in cancer cells. To overcome these challenges, microneedles (MNs) system loaded with GSH-scavenging nanocomposites was presented for nitric oxide (NO) enhanced PDT. The nanocomposites consisted of S-nitroso-N-acrylate penicillamine (SNAP; a NO donor) grafted fourth-generation polyamide amine dendrimer (G4) and chlorin e6 (Ce6). Upon local insertion of polyvinylpyrrolidone MNs, G4-SNAP/Ce6 composites were fast delivered and significantly amplified the therapeutic effects during PDT, via GSH depletion and reactive nitrogen species generation. Even with a single administration and low power light exposure, MNs with G4-SNAP/Ce6 effectively halt the tumor progression. The system demonstrated better cancer ablation efficacy than Ce6 alone toward melanoma. The strategy may inspire new ideas for future PDT-related therapy for skin tumors.

Transcriptome analysis reveals the accelerated expression of genes related to photosynthesis and chlorophyll biosynthesis contribution to shade-tolerant in Phoebe bournei

BackgroundPhoebe bournei (P. bournei) is an important and endemic wood species in China. However, the plantation, nursing, and preservation of P. bournei are often affected by light. To investigate its physiological changes and molecular mechanism of low light tolerance, two-year-old P. bournei seedlings were subjected to different shading conditions. With the increase of light intensity in the shade, the leaf color of P. bournei seedlings became darkened, the aboveground/underground biomass significantly increased, the content of chlorophyll increased and the net photosynthetic rate significantly increased.Resultsde novo transcriptome analysis showed that 724 and 3,248 genes were differentially expressed due to low light intensity at T1 (35% light exposure) and T2 (10% light exposure), respectively, when compared to the controls. Furthermore, the differentially expressed genes (DEGs) were implicated in photosynthesis, nitrogen metabolism, plant hormone signal transduction, biosynthesis of secondary metabolites, and protein processing in the endoplasmic reticulum by functional enrichment analysis. Moreover, the expression of HSP, CAB, HEMA1, GSA, DVR, MYB, bHLH, PORA, CAO, GLK, and photosystem I and II complex-related genes significantly increased after low light exposure at T2 and T1.ConclusionsThe present study suggests that the rapid growth of P. bournei seedlings under shading conditions may be the result of the accelerated expression of genes related to photosynthesis and chlorophyll biosynthesis, which enable plants to maintain a high photosynthesis rate even under low light conditions.

Low Light Exposure and Physical Activity in Older Adults With and Without Age-Related Macular Degeneration.

PurposeTo investigate the extent of low light exposure and associated physical activity in older adults with and without age-related macular degeneration (AMD).MethodsLight exposure (lux) and physical activity (counts per minute, CPM) were measured in 28 older adults (14 bilateral AMD and 14 normally sighted controls) using a wrist-worn actigraphy device (Actiwatch) for 7 days and nights. Exposure to low light levels (≤10 lux) and physical activity during waking hours were determined, as well as number of brief active periods during sleeping hours (e.g., going to the bathroom). Assessments included visual acuity and the Low Luminance Questionnaire (LLQ).ResultsNo significant differences were found in low light exposure (39 ± 14% vs. 34 ± 10%) or physical activity (200 ± 82 CPM vs. 226 ± 55 CPM) during waking hours between the AMD and control group. However, the AMD group had more brief active periods during sleeping hours than controls (1.8 ± 1.3 vs. 1.1 ± 0.4; P = 0.007). Reduced physical activity under low light levels was significantly associated with lower LLQ scores (P = 0.012).ConclusionsExposure to low light levels and associated physical activity were similar in older adults with and without AMD. This has important implications for older adults with AMD, given the impact of low light levels on visual function and mobility, suggesting the need for including lighting advice in rehabilitation programs for this population.Translational RelevanceOlder adults with and without AMD spend over a third of waking hours under low light levels, which are an environmental falls hazard. Findings suggest the need for interventions to improve lighting levels for older adults.