Environmental Light Signals Research Articles

A Light-Responsive Neural Circuit Suppresses Feeding.

Light plays an essential role in a variety of physiological processes, including vision, mood, and glucose homeostasis. However, the intricate relationship between light and an animal's feeding behavior has remained elusive. Here, we found that light exposure suppresses food intake, whereas darkness amplifies it in male mice. Interestingly, this phenomenon extends its reach to diurnal male Nile grass rats and healthy humans. We further show that lateral habenula (LHb) neurons in mice respond to light exposure, which in turn activates 5-HT neurons in the dorsal Raphe nucleus (DRN). Activation of the LHb→5-HTDRN circuit in mice blunts darkness-induced hyperphagia, while inhibition of the circuit prevents light-induced anorexia. Together, we discovered a light-responsive neural circuit that relays the environmental light signals to regulate feeding behavior in mice.

Opening the dialogue: A preliminary exploration of hair color, hair cleanliness, light, and motion effects on fNIRS signal quality.

Functional near-infrared spectroscopy (fNIRS) is a promising tool for studying brain activity, offering advantages such as portability and affordability. However, challenges in data collection persist due to factors like participant physiology, environmental light, and gross-motor movements, with limited literature on their impact on fNIRS signal quality. This study addresses four potentially influential factors-hair color, hair cleanliness, environmental light, and gross-motor movements-on fNIRS signal quality. Our aim is to raise awareness and offer insights for future fNIRS research. Six participants (4 Females, 2 Males) took part in four different experiments investigating the effects of hair color, hair cleanliness, environmental light, and gross-motor movements on fNIRS signal quality. Participants in Experiment 1, categorized by hair color, completed a finger-tapping task in a between-subjects block design. Signal quality was compared between each hair color. Participants in Experiments 2 and 3 completed a finger-tapping task in a within-subjects block design, with signal quality being compared across hair cleanliness (i.e., five consecutive days without washing the hair) and environmental light (i.e., sunlight, artificial light, no light, etc.), respectively. Experiment 4 assessed three gross-motor movements (i.e., walking, turning and nodding the head) in a within-subjects block design. Motor movements were then compared to resting blocks. Signal quality was evaluated using Scalp Coupling Index (SCI) measurements. Lighter hair produced better signals than dark hair, while the impact of environmental light remains uncertain. Hair cleanliness showed no significant effects, but gross motor movements notably reduced signal quality. Our results suggest that hair color, environmental light, and gross-motor movements affect fNIRS signal quality while hair cleanliness does not. Nevertheless, future studies with larger sample sizes are warranted to fully understand these effects. To advance future research, comprehensive documentation of participant demographics and lab conditions, along with signal quality analyses, is essential.

Exploring Embodied Cognition and Brain Dynamics under Multi-tasks Target Detection in Immerse Projector-based Augmented Reality (IPAR) Scenarios.

Embodied cognition explores the intricate interaction between the brain, body, and the surrounding environment. The advancement of mobile devices, such as immersive interactive computing and wireless electroencephalogram (EEG) devices, has presented new challenges and opportunities for studying embodied cognition. To address how mobile technology within immersive hybrid settings affects embodied cognition, we propose a target detection multitask incorporating mixed body movement interference and an environmental distraction light signal. We aim to investigate human embodied cognition in immersive projector-based augmented reality (IPAR) scenarios using wireless EEG technology. We recruited and engaged fifteen participants in four multitasking conditions: standing without distraction (SND), walking without distraction (WND), standing with distraction (SD), and walking with distraction (WD). We pre-processed the EEG data using Independent Component Analysis (ICA) to isolate brain sources and K-means clustering to categorize Independent Components (ICs). Following that, we conducted time-frequency and correlation analyses to identify neural dynamics changes associated with multitasking. Our findings reveal a decline in behavioral performance during multitasking activities. We also observed decreases in alpha and beta power in the frontal and motor cortex during standing target search tasks, decreases in theta power, and increases in alpha power in the occipital lobe during multitasking. We also noted perturbations in theta band power during distraction tasks. Notably, physical movement induced more significant fluctuations in the frontal and motor cortex than distractions from social environment light signals. Particularly in scenarios involving walking and multitasking, there was a noticeable reduction in beta suppression. Our study underscores the importance of brain-body collaboration in multitasking scenarios, where the simultaneous engagement of the body and brain in complex tasks highlights the dynamic nature of cognitive processes within the framework of embodied cognition. Furthermore, integrating immersive augmented reality technology into embodied cognition research enhances our understanding of the interplay between the body, environment, and cognitive functions, with profound implications for advancing human-computer interaction and elucidating cognitive dynamics in multitasking.

Adaptation to the shallow sea floor environment of a species of marine worms, Oligobrachia mashikoi, generally inhabiting deep-sea water

Beard worms from the family Siboglinidae, are peculiar animals and are known for their symbiotic relationships with sulfur bacteria. Most Siboglinids inhabit the deep-sea floor, thus making difficult to make any observations in situ. One species, Oligobrachia mashikoi, occurs in the shallow depths (24.5 m) of the Sea of Japan. Taking advantage of its shallow-water habitat, the first ecological survey of O. mashikoi was performed over a course of 7 years, which revealed that its tentacle-expanding behavior was dependent on the temperature and illuminance of the sea water. Furthermore, there were significantly more O. mashikoi with expanding tentacles during the nighttime than during the daytime, and the prevention of light eliminated these differences in the number of expending tentacles. These results confirmed that the tentacle-expanding behavior is controlled by environmental light signals. Consistent with this, we identified a gene encoding a photoreceptor molecule, neuropsin, in O. mashikoi, and the expression thereof is dependent on the time of day. We assume that the described behavioral response of O. mashikoi to light signals represent an adaptation to a shallow-water environment within the predominantly deep-sea taxon.

Weber’s Law of perception is a consequence of resolving the intensity of natural scintillating light and sound with the least possible error

Efficient resolution of natural light and sound intensity is essential for organisms, systems and machines that rely on visual and auditory sensory perception to survive or function effectively in their environment. This resolution obeys Weber’s Law when the smallest resolvable change, a just-noticeable-difference, grows in direct proportion to the stimulus. Here, Weber’s Law is found to be a consequence of attaining the theoretical minimum mean-square error possible, the Cramer–Rao lower bound, in resolving the intensity of naturally scintillating light and sound. The finding is based on statistics from thousands of measurements of naturally scintillating environmental light and sound signals. Remarkably, just-noticeable-differences in light and sound intensity measured over decades of psychophysical experiments with artificial sources are also found to approximately attain the respective Cramer–Rao lower bounds. Human intensity resolution is in this way optimally adapted to the natural scintillation of light and sound. Pattern recognition by simple matched-filter correlation between measured and hypothetical images cancels natural scintillation. For intensity perception obeying Weber’s Law, this is found to be advantageous and statistically optimal because perceived scintillation is independent of the underlying signal pattern. A small visual patch change or acoustic signature truncation is shown to be lost in natural signal-dependent fluctuations if perception with constant intensity resolution is attempted.

The multiple roles of salt-inducible kinases in regulating physiology.

Salt-inducible kinases (SIKs), which comprise a family of three homologous serine-threonine kinases, were first described for their role in sodium sensing but have since been shown to regulate multiple aspects of physiology. These kinases are activated or deactivated in response to extracellular signals that are cell surface receptor mediated and go on to phosphorylate multiple targets including the transcription cofactors CRTC1-3 and the class IIa histone deacetylases (HDACs). Thus, the SIK family conveys signals about the cellular environment to reprogram transcriptional and posttranscriptional processes in response. In this manner, SIKs have been shown to regulate metabolic responses to feeding/fasting, cell division and oncogenesis, inflammation, immune responses, and most recently, sleep and circadian rhythms. Sleep and circadian rhythms are master regulators of physiology and are exquisitely sensitive to regulation by environmental light and physiological signals such as the need for sleep. Salt-inducible kinases have been shown to be central to the molecular regulation of both these processes. Here, we summarize the molecular mechanisms by which SIKs control these different domains of physiology and highlight where there is mechanistic overlap with sleep/circadian rhythm control.

SlFHY3 and SlHY5 act compliantly to enhance cold tolerance through the integration of myo‐inositol and light signaling in tomato

Plants have evolved sophisticated regulatory networks to cope with dynamically changing light and temperature environments during day-night and seasonal cycles. However, the integration mechanisms of light and low temperature remain largely unclear. Here, we show that low red:far-red ratio (LR:FR) induces FAR-RED ELONGATED HYPOCOTYL3 (SlFHY3) transcription under cold stress in tomato (Solanum lycopersicum). Reverse genetic approaches revealed that knocking out SlFHY3 decreases myo-inositol accumulation and increases cold susceptibility, whereas overexpressing SlFHY3 induces myo-inositol accumulation and enhances cold tolerance in tomato plants. SlFHY3 physically interacts with ELONGATED HYPOCOTYL5 (SlHY5) to promote the transcriptional activity of SlHY5 on MYO-INOSITOL-1-PHOSPHATE SYNTHASE3 (SlMIPS3) and induce myo-inositol accumulation in tomato plants under cold stress. Disruption of SlHY5 and SlMIPS3 largely suppresses the cold tolerance of SlFHY3-overexpressing plants and myo-inositol accumulation in tomato. Furthermore, silencing of SlMIPS3 drastically reduces myo-inositol accumulation and compromises LR:FR-induced cold tolerance in tomato. Together, our results reveal a crucial role of SlFHY3 in LR:FR-induced cold tolerance in tomato and unravel a novel regulatory mechanism whereby plants integrate dynamic environmental light signals and internal cues (inositol biosynthesis) to induce and control cold tolerance in tomato plants.

Central Neural Circuits Orchestrating Thermogenesis, Sleep-Wakefulness States and General Anesthesia States.

Great progress has been made in specifically identifying the central neural circuits (CNCs) of the core body temperature (Tcore), sleep-wakefulness states (SWs), and general anesthesia states (GAs), mainly utilizing optogenetic or chemogenetic manipulations. We summarize the neuronal populations and neural pathways of these three CNCs, which gives evidence for the orchestration within these three CNCs, and the integrative regulation of these three CNCs by different environmental light signals. We also outline some transient receptor potential (TRP) channels that function in the CNCs-Tcore and are modulated by some general anesthetics, which makes TRP channels possible targets for addressing the general-anesthetics-induced-hypothermia (GAIH). We suggest this review will provide new orientations for further consummating these CNCs and elucidating the central mechanisms of GAIH.

Melatonin, circadian rhythms and glaucoma: current perspective.

Melatonin, circadian rhythms and glaucoma: current perspective.

FHY3 interacts with phytochrome B and regulates seed dormancy and germination.

Seed dormancy and germination are fundamental processes for plant propagation, both of which are tightly regulated by internal and external cues. Phytochrome B (phyB) is a major red/far-red-absorbing photoreceptor that senses light signals that modulate seed dormancy and germination. However, the components that directly transduce that signal downstream of phyB are mostly unknown. Here, we show that the transposase-derived transcription factor FAR-RED ELONGATED HYPOCOTYL3 (FHY3) inhibits seed dormancy and promotes phyB-mediated seed germination in Arabidopsis thaliana. FHY3 physically interacts with phyB in vitro and in vivo. RNA-sequencing and reverse transcription-quantitative polymerase chain reaction analyses showed that FHY3 regulates multiple downstream genes, including REVEILLE2 (RVE2), RVE7, and SPATULA (SPT). Yeast one-hybrid, electrophoresis mobility shift, and chromatin immunoprecipitation assays demonstrated that FHY3 directly binds these genes via a conserved FBS cis-element in their promoters. Furthermore, RVE2, RVE7, and GIBBERELLIN 3-OXIDASE 2 (GA3ox2) genetically act downstream of FHY3. Strikingly, light and phyB promote FHY3 protein accumulation. Our study reveals a transcriptional cascade consisting of phyB-FHY3-RVE2/RVE7/SPT-GA3ox2 that relays environmental light signals and thereby controls seed dormancy and germination.

Signal Integration in Plant Abiotic Stress Responses via Multistep Phosphorelay Signaling

Plants growing in any particular geographical location are exposed to variable and diverse environmental conditions throughout their lifespan. The multifactorial environmental pressure resulted into evolution of plant adaptation and survival strategies requiring ability to integrate multiple signals that combine to yield specific responses. These adaptive responses enable plants to maintain their growth and development while acquiring tolerance to a variety of environmental conditions. An essential signaling cascade that incorporates a wide range of exogenous as well as endogenous stimuli is multistep phosphorelay (MSP). MSP mediates the signaling of essential plant hormones that balance growth, development, and environmental adaptation. Nevertheless, the mechanisms by which specific signals are recognized by a commonly-occurring pathway are not yet clearly understood. Here we summarize our knowledge on the latest model of multistep phosphorelay signaling in plants and the molecular mechanisms underlying the integration of multiple inputs including both hormonal (cytokinins, ethylene and abscisic acid) and environmental (light and temperature) signals into a common pathway. We provide an overview of abiotic stress responses mediated via MSP signaling that are both hormone-dependent and independent. We highlight the mutual interactions of key players such as sensor kinases of various substrate specificities including their downstream targets. These constitute a tightly interconnected signaling network, enabling timely adaptation by the plant to an ever-changing environment. Finally, we propose possible future directions in stress-oriented research on MSP signaling and highlight its potential importance for targeted crop breeding.

Recognition of CCA1 alternative protein isoforms during temperature acclimation.

CCA1α and CCA1β protein variants respond to environmental light and temperature cues, and higher temperature promotes CCA1β protein production and causes its retention detectable in the cytoplasm. CIRCADIAN CLOCK ASSOCIATED1 (CCA1), as the core transcription factor of circadian clock, is involved in the regulation of endogenous circadian rhythm in Arabidopsis. Previous studies have shown that CCA1 consists of two abundant splice variants, fully spliced CCA1α and intron-retaining CCA1β. CCA1β is believed to form a nonfunctional heterodimer with CCA1α and its closed-related homolog LHY. Many studies have established that CCA1β is a transcription product, while how CCA1β protein is produced and how two CCA1 isoforms respond to environmental cues have not been elucidated. In this study, we identified CCA1α and CCA1β protein variants under different photoperiods with warm or cold temperature cycles, respectively. Our results showed that CCA1 protein production is regulated by prolonged light exposure and warm temperature. The protein levels of CCA1α and CCA1β peak in the morning, but the detection of CCA1β is dependent on immunoprecipitation enrichment at 22°C. Higher temperature of 37°C promotes CCA1β protein production and causes its retention to be detectable in the cytoplasm. Overall, our results indicate that two splice variants of the CCA1 protein respond to environmental light and temperature signals and may, therefore, maintain the circadian rhythms and give individuals the ability to adapt to environment.

To grow or not to grow ….

To grow or not to grow ….

The cold response regulator CBF1 promotes Arabidopsis hypocotyl growth at ambient temperatures.

Light and temperature are two core environmental factors that coordinately regulate plant growth and survival throughout their entire life cycle. However, the mechanisms integrating light and temperature signaling pathways in plants remain poorly understood. Here, we report that CBF1, an AP2/ERF-family transcription factor essential for plant cold acclimation, promotes hypocotyl growth under ambient temperatures in Arabidopsis. We show that CBF1 increases the protein abundance of PIF4 and PIF5, two phytochrome-interacting bHLH-family transcription factors that play pivotal roles in modulating plant growth and development, by directly binding to their promoters to induce their gene expression, and by inhibiting their interaction with phyB in the light. Moreover, our data demonstrate that CBF1 promotes PIF4/PIF5 protein accumulation and hypocotyl growth at both 22°C and 17°C, but not at 4°C, with a more prominent role at 17°C than at 22°C. Together, our study reveals that CBF1 integrates light and temperature control of hypocotyl growth by promoting PIF4 and PIF5 protein abundance in the light, thus providing insights into the integration mechanisms of light and temperature signaling pathways in plants.

Clock Gene Expression in the Eye Exhibits Circadian Oscillation and Light Responsiveness but is Not Necessary for Nocturnal Locomotor Activity of Japanese Loach, Misgurnus anguillicaudatus.

There are few model fish that are both edible and suitable for use in the laboratory. The Japanese loach (Misgurnus anguillicaudatus) is a traditional food in Japan, but is highly neglected despite its great nutritional value. To understand its circadian system and photic input pathway for synchronization of physiological activities to environmental light-dark cycles, we measured locomotor activity under light-dark and constant dark (DD) conditions. Locomotor activity was found to be higher in the nighttime than daytime, and its rhythmicity was weakened under DD conditions. The nocturnal activity of the Japanese loach is mainly controlled by environmental light, rather than the circadian clock. We explored the circadian regulation and light-responsiveness of clock gene expression in the eyes of loaches. The daily expression profiles of its mRNA revealed that most of the examined Cry and Per genes were likely regulated by internal circadian and/or environmental light signals. Among the Opsin genes transcribed in the eye, we detected the retinal photopigment porphyropsin at the protein level, which was lower than in mice. This property of loach eyes prompted us to analyze the locomotor activities of eye-enucleated fish. As a result, they still showed nocturnal circadian activity. Thus, it is likely that extraocular photoreceptive tissue(s) also contribute to the photic input pathway, although loach eyes are a circadian photosensitive tissue. This suggests that the loach mainly uses not its vision but other stimuli, such as mechanical or chemical stimuli, detected by barbels, to coordinate its nocturnal behavior.

Arabidopsis FAR-RED ELONGATED HYPOCOTYL3 Integrates Age and Light Signals to Negatively Regulate Leaf Senescence.

Leaf senescence is tightly regulated by numerous internal cues and external environmental signals. The process of leaf senescence is promoted by a low ratio of red to far-red (R:FR) light, FR light, or extended darkness and is repressed by a high ratio of R:FR light or R light. However, the precise regulatory mechanisms by which plants assess external light signals and their internal cues to initiate and control the process of leaf senescence remain largely unknown. In this study, we discovered that the light-signaling protein FAR-RED ELONGATED HYPOCOTYL3 (FHY3) negatively regulates age-induced and light-mediated leaf senescence in Arabidopsis (Arabidopsis thaliana). FHY3 directly binds to the promoter region of transcription factor gene WRKY28 to repress its expression, thus negatively regulating salicylic acid biosynthesis and senescence. Both the fhy3 loss-of-function mutant and WRKY28-overexpressing Arabidopsis plants exhibited early senescence under high R:FR light conditions, indicating that the FHY3-WRKY28 transcriptional module specifically prevents leaf senescence under high R:FR light conditions. This study reveals the physiological and molecular functions of FHY3 and WRKY28 in leaf senescence and provides insight into the regulatory mechanism by which plants integrate dynamic environmental light signals and internal cues to initiate and control leaf senescence.

FHY3 and FAR1 Integrate Light Signals with the miR156-SPL Module-Mediated Aging Pathway to Regulate Arabidopsis Flowering

In response to competition for light from their neighbors, shade-intolerant plants flower precociously to ensure reproductive success and survival. However, the molecular mechanisms underlying this key developmental switch are not well understood. Here, we show that a pair of Arabidopsis transcription factors essential for phytochrome A signaling, FAR-RED ELONGATED HYPOCOTYL3 (FHY3) and FAR-RED IMPAIRED RESPONSE1 (FAR1), regulate flowering time by integrating environmental light signals with the miR156-SPL module-mediated aging pathway. We found that FHY3 and FAR1 directly interact with three flowering-promoting SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors, SPL3, SPL4, and SPL5, and inhibit their binding to the promoters of several key flowering regulatory genes, including FRUITFUL (FUL), LEAFY (LFY), APETALA1 (AP1), and MIR172C, thus downregulating their transcript levels and delaying flowering. Under simulated shade conditions, levels of SPL3/4/5 proteins increase, whereas levels of FHY3 and FAR1 proteins decline, thus releasing SPL3/4/5 from FHY3/FAR1 inhibition to allow activation of FUL, LFY, AP1, and MIR172C and, consequently, early flowering. Taken together, these results unravel a novel mechanism whereby plants regulate flowering time by integrating environmental cues (such as light conditions) and an internal developmental program (the miR156-SPL module-mediated aging pathway).

Interplay between REVEILLE1 and RGA‐LIKE2 regulates seed dormancy and germination in Arabidopsis

Environmental light signal and GAs synergistically regulate seed dormancy and germination. The phytochrome B (phyB) photoreceptor regulates expression of the REVEILLE1 (RVE1) transcription factor, which directly inhibits GIBBERELLIN 3-OXIDASE2 transcription, suppressing GA biosynthesis. However, whether phyB-RVE1 coordinates with GA signaling in controlling seed dormancy and germination remains unknown. Here, we demonstrate that RVE1 regulation of seed dormancy and germination requires a DELLA repressor, REPRESSOR OF GA-LIKE2 (RGL2), in Arabidopsis thaliana. RVE1 interacts with both RGL2 and its E3 ubiquitin ligase SLEEPY1 (SLY1) and promotes RGL2 stability by restraining the RGL2-SLY1 interaction. Furthermore, RVE1 and RGL2 synergistically regulate global transcriptome changes; RGL2 enhances the DNA-binding capacity and transcriptional activity of RVE1 in regulating downstream gene expression. Moreover, RGL2 expression is repressed by phyB. Our study reveals a novel regulatory mechanism in which the RVE1-RGL2 module coordinately controls seed dormancy and germination by integrating light perception, GA metabolism and GA signaling pathways.

The effects of environmental light on the reorganization of chloroplasts in the resurrection of Selaginella tamariscina

ABSTRACTChloroplast repair and reorganization are crucial for the rehydration of resurrected plants. As one of the most important organelles in plant, photosynthesis takes place in chloroplasts. Meanwhile, light is important to the biosynthesis and activity regulation of chloroplasts. Here, we investigate the recovery of the chloroplasts and photosynthetic system in plant: Selaginella tamariscina under dark condition and environmental light (dark-light transition) condition. This study used the S. tamariscina grown in a culturing room, dehydrated S. tamariscina and S. tamariscina rehydrated in environmental light and dark conditions for 72 h as experimental material to measure and observed the chlorophyll content, chloroplast ultrastructure, photosynthesis, chlorophyll a fluorescence parameters. Specific leaf area and relative water content recovered in dark-rehydration conditions and were higher than those of light-rehydration, while dark-rehydration did not fully recover the chlorophyll content, net photosynthetic rate, water-use efficiency, nor the Fv/Fm. Dehydration did not destroy the chloroplast envelop, but increased the number of plastoglobules and disturbed the granum structure. As a homeochlorophyllous resurrection plant, reorganization, not the rebuilding of chloroplasts, occurs during the dehydration and rehydration processes in S. tamariscina. Environmental light signals play an important role in the recovery of photosynthetic systems.

Phototaxis in a wild isolate of the cyanobacterium Synechococcus elongatus

Many cyanobacteria, which use light as an energy source via photosynthesis, have evolved the ability to guide their movement toward or away from a light source. This process, termed "phototaxis," enables organisms to localize in optimal light environments for improved growth and fitness. Mechanisms of phototaxis have been studied in the coccoid cyanobacterium Synechocystis sp. strain PCC 6803, but the rod-shaped Synechococcus elongatus PCC 7942, studied for circadian rhythms and metabolic engineering, has no phototactic motility. In this study we report a recent environmental isolate of S. elongatus, the strain UTEX 3055, whose genome is 98.5% identical to that of PCC 7942 but which is motile and phototactic. A six-gene operon encoding chemotaxis-like proteins was confirmed to be involved in phototaxis. Environmental light signals are perceived by a cyanobacteriochrome, PixJSe (Synpcc7942_0858), which carries five GAF domains that are responsive to blue/green light and resemble those of PixJ from Synechocystis Plate-based phototaxis assays indicate that UTEX 3055 uses PixJSe to sense blue and green light. Mutation of conserved functional cysteine residues in different GAF domains indicates that PixJSe controls both positive and negative phototaxis, in contrast to the multiple proteins that are employed for implementing bidirectional phototaxis in Synechocystis.