Light-induced Regulation Research Articles

Photoactivated adenylyl cyclases attenuate sepsis-induced cardiomyopathy by suppressing macrophage-mediated inflammation.

Sepsis-induced myocardiopathy, characterized by innate immune cells infiltration and proinflammatory cytokines release, may lead to perfusion failure or even life-threatening cardiogenic shock. Macrophages-mediated inflammation has been shown to contribute to sepsis-induced myocardiopathy. In the current study, we introduced two photoactivated adenylyl cyclases (PACs), Beggiatoa sp. PAC (bPAC) and Beggiatoa sp. IS2 PAC (biPAC) into macrophages by transfection to detect the effects of light-induced regulation of macrophage pro-inflammatory response and LPS-induced sepsis-induced myocardiopathy. By this method, we uncovered that blue light-induced bPAC or biPAC activation considerably inhibited the production of pro-inflammatory cytokines IL-1 and TNF-α, both at mRNA and protein levels. Further, we assembled a GelMA-Macrophages-LED system, which consists of GelMA-a type of light crosslink hydrogel, gene modulated macrophages and wireless LED device, to allow light to regulate cardiac inflammation in situ with murine models of LPS-induced sepsis. Our results showed significant inhibition of leukocytes infiltration, especially macrophages and neutrophils, suppression of pro-inflammatory cytokines release, and alleviation of sepsis-induced cardiac dysfunction. Thus, our study may represent an emerging means to treat sepsis-induced myocardiopathy and other cardiovascular diseases by photo-activated regulating macrophage function.

Ligand Modified and Light Switched On/Off Single-Chain Magnets of {Fe 2 Co} Coordination Polymers via Metal-to-Metal Charge Transfer

Ligand Modified and Light Switched On/Off Single-Chain Magnets of {Fe ₂ Co} Coordination Polymers via Metal-to-Metal Charge Transfer

Light-responsive adsorbents with tunable adsorbent–adsorbate interactions for selective CO2 capture

Amines in porous materials have been employed as active species for the selective CO2 adsorption from natural gas because of their target-specific interactions. Nevertheless, it is difficult to modulate such strong interactions to reach a high efficiency in the adsorption processes. Herein, we fabricated light-responsive adsorbents with tunable adsorbent–adsorbate interactions for CO2 capture. The adsorbents were synthesized by introducing primary and secondary amines into a mesoporous silica that had been grafted with azobenzene groups on the surfaces. The target-specific amine sites render the adsorbents significantly selective in the uptake of CO2 over CH4, and the azobenzene groups were used as light-responsive switches to influence the adsorbent–adsorbate interactions. The adsorbents can freely adsorb CO2 when the azobenzene groups are in the trans state. Ultraviolet-light irradiation makes the azobenzene groups transform to the cis configuration, which greatly hinders amines in the uptake of CO2. The caused difference of adsorption capacity can reach 34.9%. The alternative irradiation by ultraviolet- and visible-light can lead to a recyclable regulation on adsorption performance. The changes of the electrostatic potentials of amines are responsible for the light-induced regulation on adsorption.

The PyPIF5-PymiR156a-PySPL9-PyMYB114/MYB10 module regulates light-induced anthocyanin biosynthesis in red pear

Some cultivars of pear (Pyrus L.) show attractive red fruit skin due to anthocyanin accumulation. This pigmentation can be affected by environmental conditions, especially light. To explore the light-induced regulation network for anthocyanin biosynthesis and fruit coloration in pear, small RNA libraries and mRNA libraries from fruit skins of ‘Yunhongyihao’ pear were constructed to compare the difference between bagging and debagging treatments. Analysis of RNA-seq of fruit skins with limited light (bagged) and exposed to light (debagged), showed that PyPIF5 was down-regulated after bag removal. PymiR156a was also differentially expressed between bagged and debagged fruit skins. We found that PyPIF5 negatively regulated PymiR156a expression in bagged fruits by directly binding to the G-box motif in its promoter. In addition, PymiR156a overexpression promoted anthocyanin accumulation in both pear skin and apple calli. We confirmed that PymiR156a mediated the cleavage of PySPL9, and that the target PySPL9 protein could form heterodimers with two key anthocyanin regulators (PyMYB114/PyMYB10). We proposed a new module of PyPIF5-PymiR156a-PySPL9-PyMYB114/MYB10. When the bagged fruits were re-exposed to light, PyPIF5 was down-regulated and its inhibitory effect on PymiR156a was weakened, which leads to degradation of the target PySPL, thus eliminating the blocking effect of PySPL on the formation of the regulatory MYB complexes. Ultimately, this promotes anthocyanin biosynthesis in pear skin.

Light exposure mediates circadian rhythms of rhizosphere microbial communities

Microbial community circadian rhythms have a broad influence on host health and even though light-induced environmental fluctuations could regulate microbial communities, the contribution of light to the circadian rhythms of rhizosphere microbial communities has received little attention. To address this gap, we monitored diel changes in the microbial communities in rice (Oryza sativa L.) rhizosphere soil under light–dark and constant dark regimes, identifying microbes with circadian rhythms caused by light exposure and microbial circadian clocks, respectively. While rhizosphere microbial communities displayed circadian rhythms under light–dark and constant dark regimes, taxa possessing circadian rhythms under the two conditions were dissimilar. Light exposure concealed microbial circadian clocks as a regulatory driver, leading to fewer ecological niches in light versus dark communities. These findings disentangle regulation mechanisms for circadian rhythms in the rice rhizosphere microbial communities and highlight the role of light-induced regulation of rhizosphere microbial communities.

The Aureochrome Photoreceptor PtAUREO1a Is a Highly Effective Blue Light Switch in Diatoms.

SummaryAureochromes represent a unique type of blue light photoreceptors that possess a blue light sensing flavin-binding LOV-domain and a DNA-binding bZIP domain, thus being light-driven transcription factors. The diatom Phaeodactylum tricornutum, a member of the essential marine primary producers, possesses four aureochromes (PtAUREO1a, 1b, 1c, 2). Here we show a dramatic change in the global gene expression pattern of P. tricornutum wild-type cells after a shift from red to blue light. About 75% of the genes show significantly changed transcript levels already after 10 and 60 min of blue light exposure, which includes genes of major transcription factors as well as other photoreceptors. Very surprisingly, this light-induced regulation of gene expression is almost completely inhibited in independent PtAureo1a knockout lines. Such a massive and fast transcriptional change depending on one single photoreceptor is so far unprecedented. We conclude that PtAUREO1a plays a key role in diatoms upon blue light exposure.

Effect of high light on canopy-level photosynthesis and leaf mesophyll ion flux in tomato

This study highlights the potential link between high light-induced canopy-level photosynthesis and mesophyll cell K+, Cl-, Ca2+, and H+ homeostasis in tomato. Light is a primary energy source for photosynthesis and a vital regulator of mineral nutrient uptake and distribution in plants. Plants need to optimize photosynthesis and nutrient balance in leaves for performance in fluctuating light conditions that are partially regulated by light-induced ion homeostatsis in the mesophyll cells. It is still elusive whether high light-induced leaf mesophyll ion fluxes affect leaf photosynthesis at different canopy levels in Solanum lycopersicum L. Leaf gas exchange and microelectrode ion flux (MIFE) measurements were employed to study the effects of prolonged light-induced canopy-level leaf physiological responses of tomato plants. High light resulted in a significant lowering in photosynthesis in the fully-exposed top canopy leaves of tomato, but not to mid- or low-canopy leaves. Leaf mesophyll K+ effluxes of all canopies were significantly decreased after three weeks of high light treatment. However, high light-induced leaf mesophyll Ca2+ effluxes were significantly enhanced only in the top and mid canopies. Moreover, we found that photosynthetic parameters were significantly correlated with leaf mesophyll ion fluxes. We thus propose that canopy-level significant Ca2+ efflux and K+ efflux of leaf mesophyll may serve as early indicators for light-induced regulation on photosynthesis. We conclude that light-induced differential photosynthetic performance and ion fluxes in leaves may implicate a requirement of more uniform light irradiance and spectra at different canopy levels of tall greenhouse tomato plants. This can be achieved through new innovative greenhouse lighting technologies and covering materials towards the enhancement of crop photosynthesis and yield.

Uranyl-Organic Coordination Compounds Incorporating Photoactive Vinylpyridine Moieties: Synthesis, Structural Characterization, and Light-Induced Fluorescence Attenuation.

The fluorescence of uranyl originated from electronic transitions (S11-S00 and S10-S0v, v = 0-4) of the ligand-to-metal charge transfer (LMCT) process is an intrinsic property of many uranyl coordination compounds. However, light-induced regulation on fluorescence features of uranyl hybrid materials through photoactive functional groups is less investigated. In this work, the photoactive vinyl group-containing ligands, ( E)-methyl 3-(pyridin-4-yl)acrylate and ( E)-methyl 3-(pyridin-3-yl)acrylate, have been used in the construction of uranyl coordination polymers in the presence of 1,10-phenanthroline (phen). Five compounds (UO2)3(μ3-O)(μ2-OH)2(L1)2( phen)2(1), (UO2)3(μ3-O)(μ2-OH)3(L1)( phen)2 (2), (UO2)3(μ3-O)(μ2-OH)3(L2)( phen)2 (3), [(UO2)2(μ2-OH)2(L2)2( phen)2]·2H2O (4), and (UO2)Zn(SO4)(phen)(H2O)(OH)2(5) were obtained under hydrothermal conditions. Compounds 1-4 are polynuclear uranyl structures with abundant π-π interactions and hydrogen bonds contributed to the 3D crystal packing of them. As model compounds, 1 and 3 are selected for exploring photoresponsive behaviors. The emission intensities of these two compounds are found to decrease gradually over the exposure time of UV irradiation. X-ray single crystal structural analysis suggests that the fluorescence attenuation can be explained by the slight rotation of pyridinyl groups around the carbon-carbon double bond during UV irradiation, which is accompanied by the change of weak interactions, i.e., π-π interactions and hydrogen bonds in strength and density. This feature of light-induced fluorescence attenuation may enable these two compounds to act as potential photoresponsive sensor materials.

Synergistic effects of light and temperature on anthocyanin biosynthesis in callus cultures of red-fleshed apple (Malus sieversii f. niedzwetzkyana)

We established a red callus from the leaves of a red-fleshed apple individual, which was a hybrid offspring of the cross between Malus sieversii f. niedzwetzkyana and Malus domestica cv. ‘Fuji’. We analyzed callus growth and anthocyanin biosynthesis/metabolism under different combinations of temperature and light conditions. Incubation in darkness resulted in decreased anthocyanin accumulation, while it promoted callus growth. Exposure to light and low temperature (16 °C) induced the expression of MYB10 and bHLH3/33, which are responsible for coordinating the regulation of anthocyanin biosynthesis, as well as the expression of other structural genes. Treatments with light and high temperature (32 °C) induced MYB16 expression, which repressed anthocyanin biosynthesis. Additionally, low temperature (16 °C) inhibited the expression of MYB111. We analyzed the expression patterns of MYB and bHLH transcription factor genes by quantitative real-time polymerase chain reaction. Our data suggest that light-induced regulation of anthocyanin biosynthesis is primarily caused by altered MYB10 transcript levels, while temperature-induced regulation is the result of changes to the expression of bHLH3/33, MYB16, MYB17, MYB111, and other repressors. In conclusion, we investigated the reciprocal effects of light and temperature on anthocyanin biosynthesis in red-fleshed apple calli. Our findings may provide a theoretical basis for breeding red-fleshed apple varieties with high anthocyanin contents.

New Concepts for Presynaptic Optogenetics

Optogenetics is a fast-evolving technique that employs photoreceptors to manipulate cellular activity with light. Most prominently, microbial rhodopsins are expressed in neuronal cells allowing for light-induced regulation of their respective membrane potential. While channelrhodopsin activation induces membrane depolarization, thereby triggering action potential firing, the hyperpolarizing effect of light-activated proton and chloride pumps is used for neuronal silencing. In order to broaden the palette of optogenetic applications, we aim for development of subcellularly targeted optogenetic actuators. These might be applied to study intracellular processes that underly information processing within and between neurons.Here, we describe the design and characterization of “pHoenix”, a fusion protein targeted to presynaptic vesicles. Following light application, pHoenix specifically triggers vesicular neurotransmitter uptake. Hence, expression of pHoenix in cultured neurons together with classical electrophysiology allows for correlation between presynaptic vesicular contents and respective postsynaptic responses. Moreover, pHoenix activation in combination with vesicular pH imaging might be used to study the kinetics of the underlying biochemical processes. Our results show how targeting of optogenetic actuators is crucial to decipher compartment-specific, cellular machineries that cannot be analyzed by global activation/inhibition of neurons.

Quenching in Arabidopsis thaliana Mutants Lacking Monomeric Antenna Proteins of Photosystem II

The minor light-harvesting complexes CP24, CP26, and CP29 have been proposed to play a key role in the zeaxanthin (Zx)-dependent high light-induced regulation (NPQ) of excitation energy in higher plants. To characterize the detailed roles of these minor complexes in NPQ and to determine their specific quenching effects we have studied the ultrafast fluorescence kinetics in knockout (ko) mutants koCP26, koCP29, and the double mutant koCP24/CP26. The data provide detailed insight into the quenching processes and the reorganization of the Photosystem (PS) II supercomplex under quenching conditions. All genotypes showed two NPQ quenching sites. Quenching site Q1 is formed by a light-induced functional detachment of parts of the PSII supercomplex and a pronounced quenching of the detached antenna parts. The antenna remaining bound to the PSII core was also quenched substantially in all genotypes under NPQ conditions (quenching site Q2) as compared with the dark-adapted state. The latter quenching was about equally strong in koCP26 and the koCP24/CP26 mutants as in the WT. Q2 quenching was substantially reduced, however, in koCP29 mutants suggesting a key role for CP29 in the total NPQ. The observed quenching effects in the knockout mutants are complicated by the fact that other minor antenna complexes do compensate in part for the lack of the CP24 and/or CP29 complexes. Their lack also causes some LHCII dissociation already in the dark.

Functional analysis of light-regulated promoter region of AtPolλ gene

Genetic and molecular analyses mainly in Arabidopsis and in some other plants have demonstrated involvement of light signaling in cell cycle regulation. In this report, we show light-mediated activation of the promoter of AtPolλ gene, a homolog of mammalian DNA polymerase λ in Arabidopsis thaliana and an important component of DNA damage repair/recombination machinery in plants. Analyses of the light-mediated promoter activity using various deletion versions of AtPolλ promoter in transformed Arabidopsis and tobacco (Nicotiana tabaccum) plants indicate that a 130-bp promoter region between -536 and -408 of AtPolλ promoter is essential for light-induced regulation of AtPolλ expression. DNA-protein interaction studies reveal that an ATCT-motif and AE-box light-responsive elements in the light-regulated promoter region confer light responsiveness of AtPolλ promoter. DNA-binding analysis has identified a 63-kDa trans-acting protein factor which showed specific binding to ATCT-motif, while another trans-acting factor of ~52 kDa was found to bind specifically to both ATCT and AE-box sequences. The 52-kDa protein has been identified as B3-domain transcription factor by MALDI-TOF/MS analysis. Overall, our results provide novel information on the role of light signaling in regulation of expression of an important component of DNA repair machinery in plants.

Correct biological timing inArabidopsisrequires multiple light-signaling pathways

Circadian oscillators provide rhythmic temporal cues for a range of biological processes in plants and animals, enabling anticipation of the day/night cycle and enhancing fitness-associated traits. We have used engineering models to understand the control principles of a plant's response to seasonal variation. We show that the seasonal changes in the timing of circadian outputs require light regulation via feed-forward loops, combining rapid light-signaling pathways with entrained circadian oscillators. Linear time-invariant models of circadian rhythms were computed for 3,503 circadian-regulated genes and for the concentration of cytosolic-free calcium to quantify the magnitude and timing of regulation by circadian oscillators and light-signaling pathways. Bioinformatic and experimental analysis show that rapid light-induced regulation of circadian outputs is associated with seasonal rephasing of the output rhythm. We identify that external coincidence is required for rephasing of multiple output rhythms, and is therefore important in general phase control in addition to specific photoperiod-dependent processes such as flowering and hypocotyl elongation. Our findings uncover a fundamental design principle of circadian regulation, and identify the importance of rapid light-signaling pathways in temporal control.

Lack of light-induced elevation of renal sympathetic nerve activity and plasma corticosterone levels in PACAP-deficient mice

PACAP is a neurotransmitter involved in the signal transduction of light stimulation in the suprachiasmatic nucleus (SCN). Light stimulation affects autonomic nerve activity via the SCN, and here we tested whether PACAP participates in light-induced regulation of sympatho-adrenal activity by using PACAP-deficient ( Adcyap1 −/−) mice. Light stimulation (100 lux, 30 min) significantly elevated both renal sympathetic nerve activity (RSNA), which was monitored on a digital oscilloscope, and plasma corticosterone levels in wild-type mice, but both responses were almost abolished in Adcyap1 −/− mice. Although light-induced c-Fos expression in the SCN was observed in both genotypes, the numbers of c-Fos positive cells were significantly decreased in Adcyap1 −/− mice. These data suggest that PACAP signaling pathway is involved in light-induced stimulation of RSNA and plasma corticosterone release through SCN of brain.

Photochemical DNA Activation

A new photocaged nucleoside was synthesized and incorporated into DNA with the use of standard synthesis conditions. This approach enabled the disruption of specific H-bonds and allowed for the analysis of their contribution to the activity of a DNAzyme. Brief irradiation with nonphotodamaging UV light led to rapid decaging and almost quantitative restoration of DNAzyme activity. The developed strategy has the potential to find widespread application in the light-induced regulation of oligonucleotide function.

Light-induced regulation of Ras and cdc42 proteins in the mouse visual cortex

Using synRas animals expressing permanently activated Ras in neurons, we have previously shown that intracellular neuronal Ras induces morphological changes, such as increase in the diameters of axons, associated with an enhancement of the size and ramification of dendritic trees and elevated dendritic spine density. However, the in vivo intracellular signaling pathways mediating spine plasticity are not fully known and will be investigated here. Furthermore, we ask about the possible function of normal neuronal Ras activity in the brain in response to light.

Light‐ and clock‐dependent regulation of ribosomal S6 kinase activity in the suprachiasmatic nucleus

Recent work has revealed that signalling via the p42/44 mitogen-activated protein kinase (MAPK) pathway couples light to entrainment of the circadian clock located in the suprachiasmatic nucleus (SCN). Given that many effects of the MAPK pathway are mediated by intermediate kinases, it was of interest to identify kinase targets of ERK in the SCN. One potential target is the family of 90-kDa ribosomal S6 kinases (RSKs). In this study, we examined light-induced regulation of RSK-1 in the SCN. Immunohistochemical and Western analysis were used to show that photic stimulation during the early and late night triggered the phosphorylation of RSK-1 at two sites that are targeted by ERK. This increase in the phosphorylation state of RSK-1 corresponded with an approximate fourfold increase in kinase activity. Light exposure during the subjective day did not increase the phosphorylated form of RSK-1, indicating that the capacity of light to stimulate RSK-1 activation is phase-restricted. Double immunofluorescent labelling of SCN tissue revealed the colocalized expression of the activated form of ERK with the phosphorylated form of RSK-1 following a light pulse. In vivo pharmacological inhibition of light-induced MAPK pathway activation blocked RSK-1 phosphorylation, indicating that RSK-1 activity is regulated by the MAPK pathway. PDK-1, a coregulator of RSK-1, is also expressed in the SCN and is likely to contribute to RSK-1 activity. RSK-1 phosphorylation was also rhythmically regulated within a subset of phospho-ERK-expressing cells. Together these results identify RSK-1 as a light- and clock-regulated kinase and raise the possibility that it contributes to entrainment and timing of the circadian pacemaker.

EPR study of light-induced regulation of photosynthetic electron transport in Synechocystis sp. strain PCC 6803

The kinetics of the light-induced redox changes of the photosystem 1 (PS 1) primary donor P 700 in whole cells of the cyanobacteria Synechocystis sp. PCC 6803 were studied by the electron paramagnetic resonance method. It was shown that the linear photosynthetic electron transport in cyanobacteria was controlled by two main mechanisms: (i) oxygen-dependent acceleration of electron transfer from PS 1 to NADP + due to activation of the Calvin cycle reactions and (ii) retardation of electron flow between two photosystems governed by a transmembrane proton gradient. In addition to the linear photosynthetic electron transport, cyanobacteria were capable of maintaining alternative pathways involving cyclic electron transfer around PS 1 and respiratory chains.

Genetic separation of phototropism and blue light inhibition of stem elongation.

Blue light-induced regulation of cell elongation is a component of the signal response pathway for both phototropic curvature and inhibition of stem elongation in higher plants. To determine if blue light regulates cell elongation in these responses through shared or discrete pathways, phototropism and hypocotyl elongation were investigated in several blue light response mutants in Arabidopsis thaliana. Specifically, the blu mutants that lack blue light-dependent inhibition of hypocotyl elongation were found to exhibit a normal phototropic response. In contrast, a phototropic null mutant (JK218) and a mutant that has a 20- to 30-fold shift in the fluence dependence for first positive phototropism (JK224) showed normal inhibition of hypocotyl elongation in blue light. F1 progeny of crosses between the blu mutants and JK218 showed normal phototropism and inhibition of hypocotyl elongation, and approximately 1 in 16 F2 progeny were double mutants lacking both responses. Thus, blue light-dependent inhibition of hypocotyl elongation and phototropism operate through at least some genetically distinct components.

Regulation of coupling factor in field-grown sunflower: A Redox model relating coupling factor activity to the activities of other thioredoxin-dependent chloroplast enzymes

Simultaneous, non-invasive measurements were made of the rate of photosynthetic CO2 fixation and the state of activation of the chloroplast CF1CF0-ATP synthase (CF) in field-grown sunflower (Helianthus annuus L.) during the dark-to-light transition at sunrise. CO2 fixation showed a linear response with light intensity from zero to about 500-700 μE m(-2) s(-1). However, at light intensities of only 5-22 μE m(-2) s(-1), the energetic threshold for activation of the CF was found to be significantly lowered (as compared to the pre-dawn state), presumably through reduction of the regulatory sulfhdryl groups of the γ-subunit of the CF. When these studies were extended to chamber-grown plants, it was found that as little as 5 seconds of illumination at 4 μE m(-2) s(-1) caused apparently full CF reduction. It is clear, therefore, that the catalytic activation of CF is not rate limiting to the induction of carbon assimilation under field conditions during a natural dark-to-light transition at sunrise. A model, based on the redox properties of the regulatory sulfhydryls, was developed to examine the significance of sulfhydryl midpoint potential in explaining the differences in light sensitivity and oxidation and reduction kinetics, between the CF and other thioredoxin-modulated chloroplast enzymes. Computer simulations of the light-induced regulation of three representative thioredoxin-modulated enzymes are presented.