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The biological clock of the suprachiasmatic nucleus (SCN) orchestrates circadian (approximately daily) rhythms of behaviour and physiology that underpin health. SCN cell‐autonomous time‐keeping revolves around a transcriptional/translational feedback loop (TTFL) within which PERIOD (PER1,2) and CRYPTOCHROME (CRY1,2) proteins heterodimerise and suppress trans‐activation of their encoding genes (Per1,2; Cry1,2). To explore its contribution to SCN time‐keeping, we used adeno‐associated virus–mediated translational switching to express PER2 (tsPER2) in organotypic SCN slices carrying bioluminescent TTFL circadian reporters. Translational switching requires provision of the non‐canonical amino acid, alkyne lysine (AlkK), for protein expression. Correspondingly, AlkK, but not vehicle, induced constitutive expression of tsPER2 in SCN neurons and reversibly and dose‐dependently suppressed pPer1‐driven transcription in PER‐deficient (Per1,2‐null) SCN, illustrating the potency of PER2 in negative regulation within the TTFL. Constitutive expression of tsPER2, however, failed to initiate circadian oscillations in arrhythmic PER‐deficient SCN. In rhythmic, PER‐competent SCN, AlkK dose‐dependently reduced the amplitude of PER2‐reported oscillations as inhibition by tsPER2 progressively damped the TTFL. tsPER2 also dose‐dependently lengthened the period of the SCN TTFL and neuronal calcium rhythms. Following wash‐out of AlkK to remove tsPER2, the SCN regained TTFL amplitude and period. Furthermore, SCN retained their pre‐washout phase: the removal of tsPER2 did not phase‐shift the TTFL. Given that constitutive tsCRY1 can regulate TTFL amplitude and period, but also reset TTFL phase and initiate rhythms in CRY‐deficient SCN, these results reveal overlapping and distinct properties of PER2 and CRY1 within the SCN, and emphasise the utility of translational switching to explore the functions of circadian proteins. [ABSTRACT FROM AUTHOR]

In this study, we investigate the intricate regulatory mechanisms underlying the circadian clock in Drosophila, focusing on the light‐induced conformational changes in the cryptochrome (DmCry). Upon light exposure, DmCry undergoes conformational changes that prompt its binding to Timeless and Jetlag proteins, initiating a cascade crucial for the starting of a new circadian cycle. DmCry is subsequently degraded, contributing to the desensitization of the resetting mechanism. The transient and short‐lived nature of DmCry protein–protein interactions (PPIs), leading to DmCry degradation within an hour of light exposure, presents a challenge for comprehensive exploration. To address this, we employed proximity‐dependent biotinylation techniques, combining engineered BioID (TurboID) and APEX (APEX2) enzymes with mass spectrometry. This approach enabled the identification of the in vitro DmCry interactome in Drosophila S2 cells, uncovering several novel PPIs associated with DmCry. Validation of these interactions through a novel co‐immunoprecipitation technique enhances the reliability of our findings. Importantly, our study suggests the potential of this method to reveal additional circadian clock‐ or magnetic field‐dependent PPIs involving DmCry. This exploration of the DmCry interactome not only advances our understanding of circadian clock regulation but also establishes a versatile framework for future investigations into light‐ and time‐dependent protein interactions in Drosophila. [ABSTRACT FROM AUTHOR]

Light is a critical environmental signal that is perceived by various photoreceptors and is of great significance in the photosynthetic growth of algae and plants. The phytochrome‐lacking model green alga Chlamydomonas reinhardtii possesses heme oxygenase (HMOX1) and phycocyanobilin ferredoxin oxidoreductase (PCYA1) to synthesize the linear tetrapyrrole bilin from heme in the chloroplast. The hmox1 mutant has photosynthetic growth deficiency and accumulation of photosystem I proteins such as LHCA1 is severely inhibited, and these defects could be rescued by exogenous bilin feeding in a blue light‐dependent manner. To investigate the contribution of the typical blue/ultraviolet light photoreceptors PHOT, aCRY, pCRY, and UVR8 in the process of bilin and blue light‐dependent recovery of LHCA1 protein in hmox1, we generated double mutants of these photoreceptors in hmox1, as well as a triple mutant of phot uvr8 hmox1, to analyze the LHCA1 protein abundance in these mutants. Results clearly showed that PHOT, CRYs, and UVR8 do not participate in this process. In addition, transcriptome profiling analysis of the hmox1 and its genetically complemented strain ho1C2 during dark‐to‐blue light transition revealed a total of 269 blue light‐responsive genes independent of bilin (|fold change| ≥ 2). RNA‐seq also identified a set of 249 differentially expressed genes that are dependent on both blue light and bilin. These findings provide valuable insights for elucidating the role of bilin in mediating blue light signaling pathways in Chlamydomonas. [ABSTRACT FROM AUTHOR]

Photoreceptor cryptochromes (CRYs) mediate blue‐light regulation of plant growth and development. It has been reported that Arabidopsis CRY1and CRY2 function by physically interacting with at least 84 proteins, including transcription factors or co‐factors, chromatin regulators, splicing factors, messenger RNA methyltransferases, DNA repair proteins, E3 ubiquitin ligases, protein kinases and so on. Of these 84 proteins, 47 have been reported to exhibit altered binding affinity to CRYs in response to blue light, and 41 have been shown to exhibit condensation to CRY photobodies. The blue light‐regulated composition or condensation of CRY complexes results in changes of gene expression and developmental programs. In this mini‐review, we analyzed recent studies of the photoregulatory mechanisms of Arabidopsis CRY complexes and proposed the dual mechanisms of action, including the "Lock‐and‐Key" and the "Liquid‐Liquid Phase Separation (LLPS)" mechanisms. The dual CRY action mechanisms explain, at least partially, the structural diversity of CRY‐interacting proteins and the functional diversity of the CRY photoreceptors. [ABSTRACT FROM AUTHOR]

BACKGROUND: Vibrational signal plays a crucial role in courtship communication in many insects. However, it remains unclear whether insect vibrational signals exhibit daily rhythmicity in response to changes in environmental cues. RESULTS: In this study, we observed daily rhythms of both female vibrational signals (FVS) and male vibrational signals (MVS) in the brown planthopper (BPH), Nilaparvata lugens (Stål), one of the most notorious rice pests across Asia. Notably, oscillations of FVS and MVS in paired BPHs were synchronized as part of male–female duetting interactions, displaying significant day‐night rhythmicity. Furthermore, we observed light dependency of FVS emissions under different photoperiodic regimes (18 L:6 D and 6 L:18 D) and illumination intensity levels (>300 lx, 50 lx, and 25 lx). Subsequently, the potential role of circadian clock genes cryptochromes (Nlcry1 and Nlcry2) in regulating FVS daily oscillations was examined using gene knockdown via RNA interference. We observed sharp declines and disrupted rhythms in FVS frequencies when either of the Nlcrys was downregulated, with Nlcry2 knockdown showing a more prominent effect. Moreover, we recorded a novel FVS variant (with a dominant frequency of 361.76 ± 4.31 Hz) emitted by dsNlcry1‐treated BPH females, which significantly diminished the impact of courtship stimuli on receptive males. CONCLUSION: We observed light‐dependent daily rhythms of substrate‐borne vibrational signals (SBVS) in BPH and demonstrated essential yet distinct roles of the two Nlcrys. These findings enhanced our understanding of insect SBVS and illustrated the potential of novel precision physical control strategies for disrupting mating behaviors in this rice pest. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The article discusses the history and naming of the blue UV photoreceptor "cryptochrome." The term was coined to describe an unknown photoreceptor controlling sporulation in fungi and was initially met with resistance. However, it has since been discovered in various organisms and is now widely accepted as the name for this photoreceptor. Cryptochromes have been found to control a range of functions, including circadian rhythms, magnetoreception, and signaling in plants. The article concludes by highlighting the widespread use of the term and its significance in understanding the interactions and convergence of multiple signaling pathways. [Extracted from the article]

Summary: Leaves are the main photosynthetic organs in plants, and their anatomy is optimized for light interception and gas exchange. Although each species has a characteristic leaf anatomy, which depends on the genotype, leaves also show a large degree of developmental plasticity. Light and temperature regulate leaf development from primordia differentiation to late stages of blade expansion. While the molecular mechanisms of light and temperature signaling have been mostly studied in seedlings, in the latest years, research has focused on leaf development. Here, I will describe the latest work carried out in the environmental regulation of Arabidopsis leaf development, comparing signaling mechanisms between leaves and seedlings, highlighting the new discoveries, and pointing out the most exciting open questions. [ABSTRACT FROM AUTHOR]

Summary: The development of a seedling into a photosynthetically active plant is a crucial process. Despite its importance, we do not fully understand the regulatory mechanisms behind the establishment of functional chloroplasts.We herein provide new insight into the early light response by identifying the function of three basic region/leucine zipper (bZIP) transcription factors: bZIP16, bZIP68, and GBF1. These proteins are involved in the regulation of key components required for the establishment of photosynthetically active chloroplasts. The activity of these bZIPs is dependent on the redox status of a conserved cysteine residue, which provides a mechanism to finetune light‐responsive gene expression.The blue light cryptochrome (CRY) photoreceptors provide one of the major light‐signaling pathways, and bZIP target genes overlap with one‐third of CRY‐regulated genes with an enrichment for photosynthesis/chloroplast‐associated genes. bZIP16, bZIP68, and GBF1 were demonstrated as novel interaction partners of CRY1. The interaction between CRY1 and bZIP16 was stimulated by blue light. Furthermore, we demonstrate a genetic link between the bZIP proteins and cryptochromes as the cry1cry2 mutant is epistatic to the cry1cry2bzip16bzip68gbf1 mutant.bZIP16, bZIP68, and GBF1 regulate a subset of photosynthesis associated genes in response to blue light critical for a proper greening process in Arabidopsis. [ABSTRACT FROM AUTHOR]

Detection of the genomic basis of local adaptation to environmental conditions is challenging in forest trees. Phytochromes (PHY) and cryptochromes (CRY) perceive the red (R)/far‐red (FR) and blue light respectively, thus playing a fundamental role in regulating plant growth and development. PHYO and PHYP from conifers are the equivalents of PHYA/PHYC and PHYB in angiosperms, respectively. Norway spruce shows an adaptive latitudinal cline for shade (low R:FR or FR‐enriched light) tolerance and requirement of FR light for its growth. We analyzed the exome capture data that included a uniquely large data set of 1654 Norway spruce trees sampled across many latitudes in Sweden to capture the natural clines for photoperiod and FR light exposure during the growth season. Statistically significant clinal variation was detected in allele and genotype frequencies of missense mutations in coding regions belonging to well‐defined functional domains of PHYO (PAS‐B), PHYP2 (PAS fold‐2), CRY1 (CCT1) and CRY2 (CCT2) that strongly correlates with the latitudinal gradient in response to variable light quality in Norway spruce. The missense SNP in PHYO resulting in Asn835Ser, displayed the steepest cline among all other polymorphisms. We propose that these variations in the photoreceptors represent signs of local adaptation to light quality. Summary Statement: Clinal variation was detected in the missense mutations in coding regions of phytochromes that strongly correlates with the latitudinal gradient in response to far‐red enriched light in Norway spruce. We propose that these variations represent signs of local adaptation to light quality. [ABSTRACT FROM AUTHOR]

Understanding the molecular genetic basis of animal magnet reception has been one of the big challenges in molecular biology. Recently it was discovered that the magnetic sense of Drosophila melanogaster is mediated by the ultraviolet (UV)‐A/blue light photoreceptor cryptochrome (Cry). Here, using the fruit fly as a magnet‐receptive model organism, we show that the magnetic field exposure (0.4–0.6 mT) extended lifespan under starvation, but not in cryptochrome mutant flies (cryb). The magnetic field exposure increases motor function in wild type and neurodegenerative disease model flies. Furthermore, the magnetic field exposure improved sleep quality at night‐time specific manner, but not in cryb. We also showed that repeated AC magnetic field exposure increased climbing activity in wild‐type Drosophila, but not in cryb. The data suggests that magnetic field‐dependent improvement of lifespan, sleep quality, and motor function is mediated through a cry‐dependent pathway in Drosophila. [ABSTRACT FROM AUTHOR]

The phylogenetic position of chaetognaths, or arrow worms, has been debated for decades, however recently they have been grouped into the Gnathifera, a sister clade to all other Spiralia. Chaetognath photoreceptor cells are anatomically unique by exhibiting a highly modified cilium and are arranged differently in the eyes of the various species. Studies investigating eye development and underlying gene regulatory networks are so far missing. To gain insights into the development and the molecular toolkit of chaetognath photoreceptors and eyes a new transcriptome of the epibenthic species Spadella cephaloptera was searched for opsins. Our screen revealed two copies of xenopsin and a single copy of peropsin. Gene expression analyses demonstrated that only xenopsin1 is expressed in photoreceptor cells of the developing lateral eyes. Adults likewise exhibit two xenopsin1 + photoreceptor cells in each of their lateral eyes. Beyond that, a single cryptochrome gene was uncovered and found to be expressed in photoreceptor cells of the lateral developing eye. In addition, cryptochrome is also expressed in the cerebral ganglia in a region in which also peropsin expression was observed. This condition is reminiscent of a nonvisual photoreceptive zone in the apical nervous system of the annelid Platynereis dumerilii that performs circadian entrainment and melatonin release. Cryptochrome is also expressed in cells of the corona ciliata, an organ in the posterior dorsal head region, indicating a role in circadian entrainment. Our study highlights the importance of the Gnathifera for unraveling the evolution of photoreceptors and eyes in Spiralia and Bilateria. Highlights: ‐As light‐sensitive molecules two xenopsins, a peropsin and a cryptochrome are present in developmental stages and adults of the chaetognath Spadella cephaloptera.‐Xenopsin1 appears to be the only opsin expressed in the chaetognath eyes.‐Crypotochrome and peropsin are expressed in the cerebral ganglia indicating a role in circadian entrainment. [ABSTRACT FROM AUTHOR]

Summary: The acquisition of dormancy capabilities has enabled plants to survive in adverse terrestrial environmental conditions. Dormancy accumulation and release is coupled with light signaling, which is well studied in Arabidopsis, but it is unclear in the distant nonvascular relative. We study the characteristics and function on dormancy regulation of a blue light receptor cryptochrome in Marchantia polymorpha (MpCRY).Here, we identified MpCRY via bioinformatics and mutant complement analysis. The biochemical characteristics were assessed by multiple protein‐binding assays. The function of MpCRY in gemma dormancy was clarified by overexpression and mutation of MpCRY, and its mechanism was analyzed via RNA sequencing and quantitative PCR analyses associated with hormone treatment.We found that the unique MpCRY protein in M. polymorpha undergoes both blue light‐promoted interaction with itself (self‐interaction) and blue light‐dependent phosphorylation. MpCRY has the specific characteristics of blue light‐induced nuclear localization and degradation. We further demonstrated that MpCRY transcriptionally represses abscisic acid (ABA) signaling‐related gene expression to suppress gemma dormancy, which is dependent on blue light signaling.Our findings indicate that MpCRY possesses specific biochemical and molecular characteristics, and modulates ABA signaling under blue light conditions to regulate gemma dormancy in M. polymorpha. [ABSTRACT FROM AUTHOR]

Cryptochromes (CRYs) are multifunctional molecules that act as a circadian clock oscillating factor, a blue‐light sensor, and a light‐driven magnetoreceptor. Cry genes are classified into several groups based on the evolutionary relationships. Cryptochrome 6 gene (Cry6) is present in invertebrates and lower vertebrates such as amphibians and fishes. Here we identified a Cry6 ortholog in Xenopus tropicalis (XtCry6). XtCRY6 retains a conserved long N‐terminal extension (termed CRY N‐terminal extension; CNE) that is not found in any CRY in the other groups. A structural prediction suggested that CNE contained unique structures; a tetrahelical fold structure topologically related to KaiA/RbsU domain, overlapping nuclear‐ and nucleolar‐localizing signals (NLS/NoLS), and a novel motif (termed DI‐UIM) overlapping a double‐sided ubiquitin‐interacting motif (DUIM) and an inverted ubiquitin‐interacting motif (IUIM). Potential activities of the NLS/NoLS and DI‐UIM were examined to infer the molecular function of XtCRY6. GFP‐NLS/NoLS fusion protein exogenously expressed in HEK293 cells was mostly observed in the nucleolus, while GFP‐XtCRY6 was observed in the cytoplasm. A glutathione S‐transferase (GST) pull‐down assay suggested that the DI‐UIM physically interacts with polyubiquitin. Consistently, protein docking simulations implied that XtCRY6 DI‐UIM binds two ubiquitin molecules in a relationship of a twofold rotational symmetry with the symmetry axis parallel or perpendicular to the DI‐UIM helix. These results strongly suggested that XtCRY6 does not function as a circadian transcriptional repressor and that it might have another function such as photoreceptive molecule regulating light‐dependent protein degradation or gene expression through a CNE‐mediated interaction with ubiquitinated proteins in the cytoplasm and/or nucleolus. [ABSTRACT FROM AUTHOR]

SUMMARY: The Arabidopsis COP1/SPA ubiquitin ligase suppresses photomorphogenesis in darkness. In the light, photoreceptors inactivate COP1/SPA to allow a light response. While SPA genes are specific to the green lineage, COP1 also exists in humans. This raises the question of when in evolution plant COP1 acquired the need for SPA accessory proteins. We addressed this question by generating Physcomitrium Ppcop1 mutants and comparing their visible and molecular phenotypes with those of Physcomitrium Ppspa mutants. The phenotype of Ppcop1 nonuple mutants resembles that of Ppspa mutants. Most importantly, both mutants produce green chloroplasts in complete darkness. They also exhibit dwarfed gametophores, disturbed branching of protonemata and absent gravitropism. RNA‐sequencing analysis indicates that both mutants undergo weak constitutive light signaling in darkness. PpCOP1 and PpSPA proteins form a complex and they interact via their WD repeat domains with the VP motif of the cryptochrome CCE domain in a blue light‐dependent manner. This resembles the interaction of Arabidopsis SPA proteins with Arabidopsis CRY1, and is different from that with Arabidopsis CRY2. Taken together, the data indicate that PpCOP1 and PpSPA act together to regulate growth and development of Physcomitrium. However, in contrast to their Arabidopsis orthologs, PpCOP1 and PpSPA proteins execute only partial suppression of light signaling in darkness. Hence, additional repressors may exist that contribute to the repression of a light response in dark‐exposed Physcomitrium. Significance Statement: During the water‐to‐land transition in evolution, plants had to adapt to drastically altered light conditions. Here, we investigate the mechanisms that placed the increased plant complexity evolving during terrestrialization under the control of ambient light. Moreover, our findings address when in evolution the activity of the ubiquitin ligase COP1 became dependent on the SPA accessory proteins and cryptochrome. [ABSTRACT FROM AUTHOR]

Plants possess two cryptochrome photoreceptors, cryptochrome 1 (CRY1) and cryptochrome 2 (CRY2), that mediate overlapping and distinct physiological responses. Both CRY1 and CRY2 undergo blue light‐induced phosphorylation, but the molecular details of CRY1 phosphorylation remain unclear. Here we identify 19 in vivo phosphorylation sites in CRY1 using mass spectrometry and systematically analyze the physiological and photobiochemical activities of CRY1 variants with phosphosite substitutions. We demonstrate that nonphosphorylatable CRY1 variants have impaired phosphorylation, degradation, and physiological functions, whereas phosphomimetic variants mimic the physiological functions of phosphorylated CRY1 to constitutively inhibit hypocotyl elongation. We further demonstrate that phosphomimetic CRY1 variants exhibit enhanced interaction with the E3 ubiquitin ligase COP1 (CONSTITUTIVELY PHOTOMORPHOGENIC 1). This finding is consistent with the hypothesis that phosphorylation of CRY1 is required for COP1‐dependent signaling and regulation of CRY1. We also determine that PHOTOREGULATORY PROTEIN KINASEs (PPKs) phosphorylate CRY1 in a blue light‐dependent manner and that this phosphorylation is critical for CRY1 signaling and regulation. These results indicate that, similar to CRY2, blue light‐dependent phosphorylation of CRY1 determines its photosensitivity. [ABSTRACT FROM AUTHOR]

Aphids are paradigmatic photoperiodic animals often used to study the role of the circadian clock in the seasonal response. Previously, we described some elements of the circadian clock core (genes period and timeless) and output (melatonin, AANATs and PTTH) that could have a role in the regulation of the aphid seasonal response. More recently, we identified two opsins (C‐ops and SWO4) as candidate input photoperiodic receptors. In the present report, we focus on the study of cryptochromes (cry) as photoreceptors of the circadian clock and discuss their involvement in the seasonal response. We analyse the expression of cry1 and cry2 genes in a circadian and seasonal context, and map their expression sites in the brain. We observe a robust rhythmic expression of cry2 peaking at dusk in phase with core clock genes period and timeless, while cry1 shows a weaker rhythm. Changes in cry1 and cry2 expression correlate with activation of the seasonal response, suggesting a possible link. Finally, we map the expression of cry1 and cry2 genes to clock neurons in the pars lateralis, a region essential for the photoperiodic response. Our results support a role for cry as elements of the aphid circadian clock and suggest a role in photoreception for cry1 and in clock repression for cry2. [ABSTRACT FROM AUTHOR]

The daily organisation of most mammalian cellular functions is attributed to circadian regulation of clock‐controlled protein expression, driven by daily cycles of CRYPTOCHROME‐dependent transcriptional feedback repression. To test this, we used quantitative mass spectrometry to compare wild‐type and CRY‐deficient fibroblasts under constant conditions. In CRY‐deficient cells, we found that temporal variation in protein, phosphopeptide, and K+ abundance was at least as great as wild‐type controls. Most strikingly, the extent of temporal variation within either genotype was much smaller than overall differences in proteome composition between WT and CRY‐deficient cells. This proteome imbalance in CRY‐deficient cells and tissues was associated with increased susceptibility to proteotoxic stress, which impairs circadian robustness, and may contribute to the wide‐ranging phenotypes of CRY‐deficient mice. Rather than generating large‐scale daily variation in proteome composition, we suggest it is plausible that the various transcriptional and post‐translational functions of CRY proteins ultimately act to maintain protein and osmotic homeostasis against daily perturbation. Synopsis: CRYPTOCHROMES regulate proteome composition but are not required for its circadian organisation. Loss of these global transcriptional regulators leads to proteotoxic stress, which impairs the daily organisation of physiology in both cells and mice. Circadian protein abundance, phosphorylation and ion transport do not require CRYPTOCHROMEs.CRYPTOCHROME‐deficient cells and tissues show increased proteotoxic stress.Proteotoxic stress impairs the robustness of circadian rhythms in cells and mice.CRYPTOCHROME primarily functions to suppress temporal variation in proteome composition. [ABSTRACT FROM AUTHOR]

Alcohol use disorder (AUD) is a widespread addiction disorder with severe consequences for health. AUD patients often suffer from sleep disturbances and irregular daily patterns. Conversely, disruptions of circadian rhythms are considered a risk factor for AUD and alcohol relapses. In this study, we investigated the extent to which circadian genetic and environmental disruptions and their interaction alter alcohol drinking behaviour in mice. As a model of genetic circadian disruption, we used Cryptochrome1/2‐deficient (Cry1/2−/−) mice with strongly suppressed circadian rhythms and found that they exhibit significantly reduced preference for alcohol but increased incentive motivation to obtain it. Similarly, we found that low circadian SCN amplitude correlates with reduced alcohol preference in WT mice. Moreover, we show that the low alcohol preference of Cry1/2−/− mice concurs with high corticosterone and low levels of the orexin precursor prepro‐orexin and that WT and Cry1/2−/− mice respond differently to alcohol withdrawal. As a model of environmentally induced disruption of circadian rhythms, we exposed mice to a "shift work" light/dark regimen, which also leads to a reduction in their alcohol preference. Interestingly, this effect is even more pronounced when genetic and environmental circadian perturbations interact in Cry1/2−/− mice under "shift work" conditions. In conclusion, our study demonstrates that in mice, disturbances in circadian rhythms have pronounced effects on alcohol consumption as well as on physiological factors and other behaviours associated with AUD and that the interaction between circadian genetic and environmental disturbances further alters alcohol consumption behaviour. [ABSTRACT FROM AUTHOR]

Summary: Drosophila, Arabidopsis, Synechocystis, Homo (DASH) cryptochromes belong to the cryptochrome/photolyase family and can act as DNA repair enzymes. In bacteria and fungi, they also can play regulatory roles, but in plants their biological functions remain elusive. Here, we characterize CRY‐DASH1 from the green alga Chlamydomonas reinhardtii.We perform biochemical and in vitro photochemical analysis. For functional characterization, a knock‐out mutant of cry‐dash1 is used.CRY‐DASH1 protein is localized in the chloroplast and accumulates at midday. Although the photoautotrophic growth of the mutant is significantly reduced compared to the wild‐type (WT), the mutant has increased levels of photosynthetic pigments and a higher maximum photochemical efficiency of photosystem II (PS II). Hyper‐stacking of thylakoid membranes occurs together with an increase in proteins of the PS II reaction center, D1 and its antenna CP43, but not of their transcripts. CRY‐DASH1 binds fully reduced flavin adenine dinucleotide and the antenna 5,10‐methenyltetrahydrofolate, leading to an absorption peak in the UV‐A range. Supplementation of white light with UV‐A increases photoautotrophic growth of the WT but not of the cry‐dash1 mutant.These results suggest a balancing function of CRY‐DASH1 in the photosynthetic machinery and point to its role as a photoreceptor for the UV‐A range separated from the absorption of photosynthetic pigments. [ABSTRACT FROM AUTHOR]

Cryptochromes (CRYs) function as blue light photoreceptors in diverse physiological processes in nearly all kingdoms of life. Over the past several decades, they have emerged as the most likely candidates for light‐dependent magnetoreception in animals, however, a long history of conflicts between in vitro photochemistry and in vivo behavioral data complicate validation of CRYs as a magnetosensor. In this review, we highlight the origins of conflicts regarding CRY photochemistry and signal transduction, and identify recent data that provides clarity on potential mechanisms of signal transduction in magnetoreception. The review primarily focuses on examining differences in photochemistry and signal transduction in plant and animal CRYs, and identifies potential modes of convergent evolution within these independent lineages that may identify conserved signaling pathways. [ABSTRACT FROM AUTHOR]

Summary: Ferns appear in the fossil record some 200 Myr before angiosperms. However, as angiosperm‐dominated forest canopies emerged in the Cretaceous period there was an explosive diversification of modern (leptosporangiate) ferns, which thrived in low, blue‐enhanced light beneath angiosperm canopies. A mechanistic explanation for this transformative event in the diversification of ferns has remained elusive.We used physiological assays, transcriptome analysis and evolutionary bioinformatics to investigate a potential connection between the evolution of enhanced stomatal sensitivity to blue light in modern ferns and the rise of angiosperm‐dominated forests in the geological record.We demonstrate that members of the largest subclade of leptosporangiate ferns, Polypodiales, have significantly faster stomatal response to blue light than more ancient fern lineages and a representative angiosperm. We link this higher sensitivity to levels of differentially expressed genes in blue‐light signaling, particularly in the cryptochrome (CRY) signaling pathway. Moreover, CRYs of the Polypodiales examined show gene duplication events between 212.9–196.9 and 164.4–151.8 Ma, when angiosperms were emerging, which are lacking in other major clades of extant land plants.These findings suggest that evolution of stomatal blue‐light sensitivity helped modern ferns exploit the shady habitat beneath angiosperm forest canopies, fueling their Cretaceous hyperdiversification. See also the Commentary on this article by Chater, 230: 886–888. [ABSTRACT FROM AUTHOR]

Cryptochrome 2 (Cry2) is a core clock gene important for circadian regulation. It has also been associated with anxiety and depressive‐like behaviors in mice, but the previous findings have been conflicting in terms of the direction of the effect. To begin to elucidate the molecular mechanisms of this association, we carried out behavioral testing, PET imaging, and gene expression analysis of Cry2−/− and Cry2+/+ mice. Compared to Cry2+/+ mice, we found that Cry2−/− mice spent less time immobile in the forced swim test, suggesting reduced despair‐like behavior. Moreover, Cry2−/− mice had lower saccharin preference, indicative of increased anhedonia. In contrast, we observed no group differences in anxiety‐like behavior. The behavioral changes were accompanied by lower metabolic activity of the ventro‐medial hypothalamus, suprachiasmatic nuclei, ventral tegmental area, anterior and medial striatum, substantia nigra, and habenula after cold stress as measured by PET imaging with a glucose analog. Although the expression of many depression‐associated and metabolic genes was upregulated or downregulated by cold stress, we observed no differences between Cry2−/− and Cry2+/+ mice. These findings are consistent with other studies showing that Cry2 is required for normal emotional behavior. Our findings confirm previous roles of Cry2 in behavior and extend them by showing that the effects on behavior may be mediated by changes in brain metabolism. [ABSTRACT FROM AUTHOR]

Circadian rhythms are a pervasive property of mammalian cells, tissues and behaviour, ensuring physiological adaptation to solar time. Models of cellular timekeeping revolve around transcriptional feedback repression, whereby CLOCK and BMAL1 activate the expression of PERIOD (PER) and CRYPTOCHROME (CRY), which in turn repress CLOCK/BMAL1 activity. CRY proteins are therefore considered essential components of the cellular clock mechanism, supported by behavioural arrhythmicity of CRY‐deficient (CKO) mice under constant conditions. Challenging this interpretation, we find locomotor rhythms in adult CKO mice under specific environmental conditions and circadian rhythms in cellular PER2 levels when CRY is absent. CRY‐less oscillations are variable in their expression and have shorter periods than wild‐type controls. Importantly, we find classic circadian hallmarks such as temperature compensation and period determination by CK1δ/ε activity to be maintained. In the absence of CRY‐mediated feedback repression and rhythmic Per2 transcription, PER2 protein rhythms are sustained for several cycles, accompanied by circadian variation in protein stability. We suggest that, whereas circadian transcriptional feedback imparts robustness and functionality onto biological clocks, the core timekeeping mechanism is post‐translational. SYNOPSIS: CRYPTOCHROME (CRY) proteins are central regulators of the circadian clock transcription/translation feedback loop. The finding that circadian timekeeping persists, albeit with reduced robustness, in CRY‐deficient cells and mice suggests that clock gene activity is determined by evolutionarily‐conserved post‐translational timing mechanisms. CRY‐mediated transcriptional feedback is dispensable for circadian timekeeping in mammalian cells, but functions to make rhythms more robust.CRY knockout mice exhibit behavioural rhythmicity under specific environmental conditions.Circadian variation in the abundance of core clock component PER2 is amplified by, but does not require, rhythmic Per2 transcription.CK1 and GSK3 kinases regulate PER2 stability in the absence of CRY. [ABSTRACT FROM AUTHOR]

This article is a Commentary on Liu et al. (2022), 234: 1332–1346 and Miao et al. (2022), 234: 1347–1362. [ABSTRACT FROM AUTHOR]

Circadian disruption influences metabolic health. Metabolism modulates circadian function. However, the mechanisms coupling circadian rhythms and metabolism remain poorly understood. Here, we report that cystathionine β‐synthase (CBS), a central enzyme in one‐carbon metabolism, functionally interacts with the core circadian protein cryptochrome 1 (CRY1). In cells, CBS augments CRY1‐mediated repression of the CLOCK/BMAL1 complex and shortens circadian period. Notably, we find that mutant CBS‐I278T protein, the most common cause of homocystinuria, does not bind CRY1 or regulate its repressor activity. Transgenic CbsZn/Zn mice, while maintaining circadian locomotor activity period, exhibit reduced circadian power and increased expression of E‐BOX outputs. CBS function is reciprocally influenced by CRY1 binding. CRY1 modulates enzymatic activity of the CBS. Liver extracts from Cry1−/− mice show reduced CBS activity that normalizes after the addition of exogenous wild‐type (WT) CRY1. Metabolomic analysis of WT, CbsZn/Zn, Cry1−/−, and Cry2−/− samples highlights the metabolic importance of endogenous CRY1. We observed temporal variation in one‐carbon and transsulfuration pathways attributable to CRY1‐induced CBS activation. CBS‐CRY1 binding provides a post‐translational switch to modulate cellular circadian physiology and metabolic control. [ABSTRACT FROM AUTHOR]

Many psychiatric disorders, for example, anxiety, are accompanied by disturbances of circadian rhythms, including disturbed sleep/wake cycles, changes in locomotor activity, and abnormal endocrine function. Conversely, alternations of circadian rhythms are a risk factor for the development of psychiatric disorders. This assumption is supported by animals with clock gene mutations which often display behaviors that resemble human psychiatric disorders. In this study, we performed an in‐depth behavioral analysis with male mice lacking the central clock genes Cryptochrome 1 and 2 (Cry1/2−/−), which are thus unable to express endogenous circadian rhythms. With wild‐type and Cry1/2−/− mice, we performed an extensive behavioral analysis to study their cognitive abilities, social behavior, and their expression of depression‐like and anxiety‐like behavior. While Cry1/2−/− mice showed only mild abnormalities at cognitive and social behavioral levels, they were consistently more anxious than wildtype mice. Anxiety‐like behavior was particularly evident in reduced mobility in new environments, altered ability to habituate, compensatory behavior, and consistent restless behavior across many behavioral tests. In line with their anxiety‐like behavioral phenotype, Cry1/2−/− mice have higher c‐Fos activity in the amygdala after exposure to an anxiogenic stressor than wild‐type mice. In our study, we identified Cry1/2−/− mice as animals that qualify as a translational mouse model for anxiety disorder in humans because of its consistent behavior of restlessness, increased immobility, and dysfunctional habituation in new environments. [ABSTRACT FROM AUTHOR]

SUMMARY: In Arabidopsis, stamen elongation, which ensures male fertility, is controlled by the auxin response factor ARF8, which regulates the expression of the auxin repressor IAA19. Here, we uncover a role for light in controlling stamen elongation. By an extensive genetic and molecular analysis we show that the repressor of light signaling COP1, through its targets HY5 and HYH, controls stamen elongation, and that HY5 – oppositely to ARF8 – directly represses the expression of IAA19 in stamens. In addition, we show that in closed flower buds, when light is shielded by sepals and petals, the blue light receptors CRY1/CRY2 repress stamen elongation. Coherently, at flower disclosure and in subsequent stages, stamen elongation is repressed by the red and far‐red light receptors PHYA/PHYB. In conclusion, different light qualities – sequentially perceived by specific photoreceptors – and the downstream COP1–HY5/HYH module finely tune auxin‐induced stamen elongation and thus male fertility. Significance Statement: In Arabidopsis auxin‐induced stamen elongation is essential for optimizing the transfer of pollen grains onto the pistil to allow successful fertilization. Here we show that different light qualities, via the conserved COP1–HY5/HYH module, finely tune auxin‐induced stamen elongation and thus male fertility. [ABSTRACT FROM AUTHOR]

The photoreceptors UV RESISTANCE LOCUS 8 (UVR8) and CRYPTOCHROMES 1 and 2 (CRYs) play major roles in the perception of UV‐B (280–315 nm) and UV‐A/blue radiation (315–500 nm), respectively. However, it is poorly understood how they function in sunlight. The roles of UVR8 and CRYs were assessed in a factorial experiment with Arabidopsis thaliana wild‐type and photoreceptor mutants exposed to sunlight for 6 or 12 hr under five types of filters with cut‐offs in UV and blue‐light regions. Transcriptome‐wide responses triggered by UV‐B and UV‐A wavelengths shorter than 350 nm (UV‐Asw) required UVR8 whereas those induced by blue and UV‐A wavelengths longer than 350 nm (UV‐Alw) required CRYs. UVR8 modulated gene expression in response to blue light while lack of CRYs drastically enhanced gene expression in response to UV‐B and UV‐Asw. These results agree with our estimates of photons absorbed by these photoreceptors in sunlight and with in vitro monomerization of UVR8 by wavelengths up to 335 nm. Motif enrichment analysis predicted complex signaling downstream of UVR8 and CRYs. Our results highlight that it is important to use UV waveband definitions specific to plants' photomorphogenesis as is routinely done in the visible region. How UVR8 and cryptochrome photoreceptors function in the natural environment remains poorly understood. We show that transcriptome responses to solar UV‐B and UV‐A below 350 nm (UVsw) are mediated by UVR8 whereas those induced by blue and UV‐A longer than 350 nm require cryptochromes. UVR8 modulates blue light induced changes in gene expression while cryptochromes antagonize solar UVsw responses mediated by UVR8. [ABSTRACT FROM AUTHOR]

Large molecular machines regulate daily cycles of transcriptional activity and help generate rhythmic behavior. In recent years, structural and biochemical analyses have elucidated a number of principles guiding the interactions of proteins that form the basis of circadian timing. In its simplest form, the circadian clock is composed of a transcription/translation feedback loop. However, this description elides a complicated process of activator recruitment, chromatin decompaction, recruitment of coactivators, expression of repressors, formation of a repressive complex, repression of the activators, and ultimately degradation of the repressors and reinitiation of the cycle. Understanding the core principles underlying the clock requires careful examination of molecular and even atomic level details of these processes. Here, we review major structural and biochemical findings in circadian biology and make the argument that shared protein interfaces within the clockwork are critical for both the generation of rhythmicity and timing of the clock. [ABSTRACT FROM AUTHOR]

Life on earth is assumed to have developed in tropical regions that are characterized by regular 24 hr cycles in irradiance and temperature that remain the same throughout the seasons. All organisms developed circadian clocks that predict these environmental cycles and prepare the organisms in advance for them. A central question in chronobiology is how endogenous clocks changed in order to anticipate very different cyclical environmental conditions such as extremely short and long photoperiods existing close to the poles. Flies of the family Drosophilidae can be found all over the world—from the tropics to subarctic regions—making them unprecedented models for studying the evolutionary processes that underlie the adaptation of circadian clocks to different latitudes. This review summarizes our current understanding of these processes. We discuss evolutionary changes in the clock genes and in the clock network in the brain of different Drosophilids that may have caused behavioural adaptations to high latitudes. [ABSTRACT FROM AUTHOR]

Summary: BRI1‐EMS‐SUPPRESSOR 1 (BES1) functions as a key regulator in the brassinosteroid (BR) pathway that promotes plant growth. However, whether BES1 is involved in photoperiodic flowering is unknown.Here we report that BES1 acts as a positive regulator of photoperiodic flowering, but it cannot directly bind FLOWERING LOCUS T (FT) promoter. BR ENHANCED EXPRESSION 1 (BEE1) is the direct target of BES1 and acts downstream of BES1. BEE1 is also a positive regulator of photoperiodic flowering. BEE1 binds directly to the FT chromatin to activate the transcription of FT and promote flowering initiation.More importantly, BEE1 promotes flowering in a blue light photoreceptor CRYPTOCHROME 2 (CRY2)  partially dependent manner, as it physically interacts with CRY2 under the blue light. Furthermore, BEE1 is regulated by both BRs and blue light. The transcription of BEE1 is induced by BRs, and the BEE1 protein is stabilized under the blue light.Our findings indicate that BEE1 is the integrator of BES1 and CRY2 mediating flowering, and BES1‐BEE1‐FT is a new signaling pathway in regulating photoperiodic flowering. [ABSTRACT FROM AUTHOR]

The mechanisms of magnetoreception have been proposed as the magnetite‐based, the chemical radical‐pair and biocompass model, in which magnetite particles, the cryptochrome (Cry) or iron‐sulfur cluster assembly 1 (IscA1) may be involved. However, little is known about the association among the molecules. Here we investigated the molecular characterization and the mRNA expression of IscA1 in different developmental stages, tissues and magnetic fields in the migratory brown planthopper (BPH), Nilaparvata lugens. NlIscA1 contains an open reading frame of 390 bp, encoding amino acids of 129, with the predicted molecular weight of 14.0 kDa and the isoelectric point of 9.10. Well‐conserved Fe‐S cluster binding sites were observed in the predicted protein. Phylogenetic analysis demonstrated NlIscA1 to be clustered into the insect's IscA1. NlIscA1 showed up‐regulated mRNA expression during the period of migration. The mRNA expression of NlIscA1 could be detected in all the three tissues of head, thorax and abdomen, with the highest expression level in the abdomen. For the macropterous migratory Nilaparvata lugens, mRNA expression of NlIscA1 and N. lugens cryptochrome1 (Nlcry1) were up‐regulated under the magnetic fields of 5 Gauss and 10 Gauss in strength (vs. local geomagnetic field), while N. lugens cryptochrome2 (Nlcry2) remained stable. For the brachyterous non‐migratory Nilaparvata lugens, no significant changes were found in mRNA expression of NlIscA1, Nlcry1 and Nlcry2 among different magnetic fields. These findings preliminarily reveal that the expression of NlIscA1 and Nlcry1 exhibited coordinated responses to the magnetic field. It suggests some potential associations among the putative magneto‐sensitive molecules of cryptochrome and iron‐sulfur cluster assembly. [ABSTRACT FROM AUTHOR]

This article is a Commentary on Cai et al. (2021), 230: 1201–1213. [ABSTRACT FROM AUTHOR]

Diapause is a strategy used by many insects living in temperate zones to survive the winter. The most reliable environmental cue to induce diapause is photoperiod, for which day or night length is measured by a mechanism called the photoperiodic clock. Despite several studies in insects, the photoperiodic mechanisms remain unclear. In the present study, we show that cryptochromes (crys) mediate photoperiodic responses in the cricket Modicogryllus siamensis. Nymphal development of M. siamensis is highly dependent on photoperiod: under long‐day conditions, most nymphs become adults within 60 days after hatching by undergoing seven moults, whereas, under short‐day conditions, they take much longer (approximately 180 days), with an increased number of moults. Similar to most insects, the cricket has two cry genes: the Drosophila type cry (Ms'cry1) and the mammalian type cry (Ms'cry2). Ms'cry1 shows some constitutive expression, whereas Ms'cry2 is rhythmically expressed under both long‐day and short‐day conditions. Parental RNA interference against either or both of the two cry genes partially prevents the long‐day responses, whereas inhibition of Ms'cry1 or Ms'cry1/Ms'cry2 enhances the short‐day response with a further delay of adult emergence or its complete prevention, respectively. Nymphal RNA interference of Ms'crys at the fourth‐instar stage delays adult emergence and increases the number of moults under long‐day conditions. We hypothesize that Ms'cry genes are involved not only in the photoperiodic mechanism, but also in the regulatory mechanism of nymphal development downstream of the photoperiodic clock in the cricket M. siamensis. Parental RNA interference against either or both of Ms'cry1 and Ms'cry2 partially prevents long‐day responses, whereas inhibition of Ms'cry1 or Ms'cry1/Ms'cry2 enhances or completely prevents short‐day responses, respectively, in Modicogryllus siamensis.Nymphal RNA interference of Ms'crys at the fourth‐instar stage delays adult emergence and increases the number of moults under long‐day conditions.Ms'cry genes are probably involved not only in the photoperiodic mechanism, but also in the regulatory mechanism of nymphal development downstream of the photoperiodic clock in M. siamensis. [ABSTRACT FROM AUTHOR]

Summary: Cryptochrome (cry) blue light photoreceptors have important roles in the regulation of plant development. Their photocycle includes redox changes of their flavin adenine dinucleotide (FAD) chromophore, which is fully oxidised in the dark state and semi‐reduced in the signalling‐active lit state. The two Arabidopsis thaliana cryptochromes, cry1 and cry2, and the plant‐type cryptochrome CPH1 from Chlamydomonas rheinhardtii bind ATP and other nucleotides. Binding of ATP affects the photocycle of these photoreceptors and causes structural alterations. However, the exact regions that undergo structural changes have not been defined, and most importantly it is not known whether ATP binding affects the biological activity of these photoreceptors in planta. Here we present studies on the effect of ATP on Arabidopsis cry2. Recombinant cry2 protein showed a high affinity for ATP (KD of 1.09 ± 0.48 μm). Binding of ATP and other adenines promoted photoreduction of the FAD chromophore in vitro and caused structural changes, particularly in α‐helix 21 which links the photosensory domain with the C‐terminal extension. The constructed cry2Y399A mutant was unable to bind ATP and did not show enhancement of photoreduction by ATP. When this mutant gene was expressed in Arabidopsis null cry2 mutant plants it retained some biological activity, which was, however, lower than that of the wild type. Our results indicate that binding of ATP to cry2, and most likely to other plant‐type cryptochromes, is not essential but boosts the formation of the signalling state and biological activity. Significance Statement: Binding of ATP by plant cryptochromes enhances signalling state formation, but how this affects the biological activity of these blue light photoreceptors was unknown. Here we show that a mutant of Arabidopsis thaliana cry2, which is unable to bind ATP, is still biologically active but to a smaller degree than the wild‐type photoreceptor. Thus, binding of ATP to cry2 in vivo is relevant for its biological function. [ABSTRACT FROM AUTHOR]

Abstract: Cryptochromes are photolyase‐like photoreceptors. Arabidopsis CRY2 (cryptochrome 2) primarily mediates the photoperiodic regulation of floral initiation. CRY2 has been shown to promote FT (FLOWERING LOCUS T) mRNA expression in response to blue light by suppressing the degradation of the CO (CONSTANS) protein and activating CIB1 (CRY2‐interacting bHLH1). Although CIB1 and CO are both transcriptional activators of FT, their relationship is unknown. Here, we show that CIB1 physically interacts with CO and promotes FT transcription in a CO‐dependent manner. CRY2, CIB1, and CO form a protein complex in response to blue light to activate FT transcription, and the complex is regulated by the photoperiod and peaks at dusk along with higher FT expression. We also determined that CRY2 was recruited to the FT chromatin by CIB1 and CO and that all three proteins are bound to the same region within the FT promoter. Therefore, there is crosstalk between the CRY2‐CO and CRY2‐CIBs pathways, and CIB1 and CO act together to regulate FT transcription and flowering. [ABSTRACT FROM AUTHOR]

Abstract: The production of anthocyanin is regulated by light and corresponding photoreceptors. In this study, we found that exposure to blue light and overexpression of CRY1a are associated with increased accumulation of anthocyanin in tomato (Solanum lycopersicum L.). These responses are the result of changes in mRNA and the protein levels of SlHY5, which is a transcription factor. In vitro and in vivo experiments using electrophoretic mobility shift assay and ChIP‐qPCR assays revealed that SlHY5 could directly recognize and bind to the G‐box and ACGT‐containing element in the promoters of anthocyanin biosynthesis genes, such as chalcone synthase 1, chalcone synthase 2, and dihydroflavonol 4‐reductase. Silencing of SlHY5 in OE‐CRY1a lines decreased the accumulation of anthocyanin. The findings presented here not only deepened our understanding of how light controls anthocyanin biosynthesis and associated photoprotection in tomato leaves, but also allowed us to explore potential targets for improving pigment production. [ABSTRACT FROM AUTHOR]

Abstract: Background: Various endocrine signals oscillate over the 24‐hour period and so does the responsiveness of target tissues. These daily oscillations do not occur solely in response to external stimuli but are also under the control of an intrinsic circadian clock. Design: We searched the PubMed database to identify studies describing the associations of clock genes with endocrine diseases. Results: Various human single nucleotide polymorphisms of brain and muscle ARNT‐like 1 (BMAL1) and Circadian Locomotor Output Cycles Kaput (CLOCK) genes exhibited significant associations with type 2 diabetes mellitus. ARNTL2 gene expression and upregulation of BMAL1 and PER1 were associated with the development of type 1 diabetes mellitus. Thyroid hormones modulated PER2 expression in a tissue‐specific way, whereas BMAL1 regulated the expression of type 2 iodothyronine deiodinase in specific tissues. Adrenal gland and adrenal adenoma expressed PER1, PER2, CRY2, CLOCK and BMAL1 genes. Adrenal sensitivity to adrenocorticotrophin was also affected by circadian oscillations. A significant correlation between the expression of propio‐melanocorticotrophin and PER 2, as well as between prolactin and CLOCK, was found in corticotroph and lactosomatotroph cells, respectively, in the pituitary. Clock genes and especially BMAL1 showed an important role in fertility, whereas oestradiol and androgens exhibited tissue‐specific effects on clock gene expression. Metabolic disorders were also associated with circadian dysregulation according to studies in shift workers. Conclusions: Clock genes are associated with various endocrine disorders through complex mechanisms. However, data on humans are scarce. Moreover, clock genes exhibit a tissue‐specific expression representing an additional level of regulation. Their specific role in endocrine disorders and their potential implications remain to be further clarified. [ABSTRACT FROM AUTHOR]

Abstract: Blue light photoreceptors, cryptochromes (CRYs), regulate multiple aspects of plant growth and development. However, our knowledge of CRYs is predominantly based on model plant Arabidopsis at early growth stage. In this study, we elucidated functions of CRY1a gene in mature tomato (Solanum lycopersicum) plants by using cry1a mutants and CRY1a‐overexpressing lines (OE‐CRY1a‐1 and OE‐CRY1a‐2). In comparison with wild‐type plants, cry1a mutants are relatively tall, accumulate low biomass, and bear more fruits, whereas OE‐CRY1a plants are short stature, and they not only flower lately but also bear less fruits. RNA‐seq, qRT‐PCR, and LC‐MS/MS analysis revealed that biosynthesis of gibberellin, cytokinin, and jasmonic acid was down‐regulated by CRY1a. Furthermore, DNA replication was drastically inhibited in leaves of OE‐CRY1a lines, but promoted in cry1a mutants with concomitant changes in the expression of cell cycle genes. However, CRY1a positively regulated levels of soluble sugars, phytofluene, phytoene, lycopene, and ß‐carotene in the fruits. The results indicate the important role of CRY1a in plant growth and have implications for molecular interventions of CRY1a aimed at improving agronomic traits. [ABSTRACT FROM AUTHOR]

Exaptations are adaptations that have undergone a major change in function. By recruiting genes from sources originally unrelated to vision, exaptation has allowed for sudden and critical photosensory innovations, such as lenses, photopigments, and photoreceptors. Here we review new or neglected findings, with an emphasis on unicellular eukaryotes (protists), to illustrate how exaptation has shaped photoreception across the tree of life. Protist phylogeny attests to multiple origins of photoreception, as well as the extreme creativity of evolution. By appropriating genes and even entire organelles from foreign organisms via lateral gene transfer and endosymbiosis, protists have cobbled photoreceptors and eyespots from a diverse set of ingredients. While refinement through natural selection is paramount, exaptation helps illustrate how novelties arise in the first place, and is now shedding light on the origins of photoreception itself. [ABSTRACT FROM AUTHOR]

Cryptochromes (CRYs) are blue and UV light photoreceptors, known to play key roles in circadian rhythms and in the light-dependent magnetosensitivity of insects. Two novel cryptochrome genes were cloned from the brown planthopper, and were given the designations of Nlcry1 and Nlcry2, with the accession numbers KM108578 and KM108579 in GenBank. The complementary DNA sequences of Nlcry1 and Nlcry2 are 1935 bp and 2463 bp in length, and they contain an open reading frame of 1629 bp and 1872 bp, encoding amino acids of 542 and 623, with a predicted molecular weight of 62.53 kDa and 70.60 kDa, respectively. Well-conserved motifs such as DNA-photolyase and FAD-binding-7 domains were observed in Nlcry1 and Nlcry2. Phylogenetic analysis demonstrated the proteins of Nlcry1 and Nlcry2 to be clustered into the insect's cryptochrome 1 and cryptochrome 2, respectively. Quantitative polymerase chain reaction showed that the daily oscillations of messenger RNA (mRNA) expression in the head of the brown planthopper were mild for Nlcry1, and modest for Nlcry2. Throughout all developmental stages, Nlcry1 and Nlcry2 exhibited extreme fluctuations and distinctive expression profiles. Cryptochrome mRNA expression peaked immediately after adult emergence and then decreased subsequently. The tissue expression profiles of newly emerged brown planthopper adults showed higher expression levels of CRYs in the head than in the thorax or abdomen, as well as significantly higher levels of CRYs in the heads of the macropterous strain than in the heads of the brachypterous strain. Taken together, the results of our study suggest that the two cryptochrome genes characterized in the brown planthopper might be associated with developmental physiology and migration. [ABSTRACT FROM AUTHOR]

Photolyases are efficient DNA repair enzymes that specifically repair either cyclobutane pyrimidine dimers or (6-4) photoproducts in a light-dependent cleavage reaction. The closely related classical cryptochrome blue light photoreceptors do not repair DNA lesions; instead they are involved in regulatory processes. CryB of Rhodobacter sphaeroides was until now described as a cryptochrome that affects light-dependent and singlet oxygen-dependent gene expression and is unusual in terms of its cofactor composition. Here we present evidence for a repair activity of (6-4) photoproducts by CryB and suggest a dual character combining the functions of cryptochromes and photolyases. We investigated the effects of crucial amino acids involved in cofactor or DNA lesion binding on the light-dependent recovery of cells after UV light exposure ( in vivo photoreactivation). Remarkably, impairment of one of the two light absorbing cofactors, FAD or 6,7-dimethyl-8-ribityllumazine, only marginally affected the final survival rate but strongly decelerated photoreactivation kinetics. The impairment of both of them together through mutagenesis decreased CryB-dependent photoreactivation to the level of the ∆ cryB knockout strain. The third cofactor, a [4Fe4S] iron-sulfur cluster, is indispensable for the structural integrity of the protein. The reduction of FAD via the conserved tryptophan W338, which is crucial for in vitro reduction and consequently DNA repair, is not required for in vivo photoreactivation, suggesting that this reduction pathway to FAD is dispensable in the cellular environment. This demonstrates that in vitro experiments give only limited information on in vivo photolyase activity. [ABSTRACT FROM AUTHOR]

The article presents the result of a study which examined DNA repair through photolyase in Escherichia coli and nucleotide excision repair in both microorganism and humans. The variables considered include the role of the (UVrA)2 homodimer in identifying the DNA damage site, the mechanism of Escherichia coli transcription-coupled repair, and excision DNA repair in humans. A discussion on the excision repair map of the human genome at single nucleotide resolution is offered.

Predictable seasonal change in photoperiod triggers a sequential change in the daily activity-rest pattern, adaptive for migration in several bird species. The night-migratory black-headed bunting (Emberiza melanocephala) is day active under short photoperiods (8 h light:16 h dark, short day sensitive). Under long photoperiods (16 h light:8 h dark), the buntings are initially day active (long day premigratory) but subsequently become intensely night active (long day migratory) and after few weeks again return to a day active pattern (long day refractory). However, it is unclear how the daily expression of circadian genes changes during photoperiod-induced seasonal life-history states (LHSs). We measured period 2 (Per2), cryptochrome 1 (Cry1), brain and muscle arnt-like protein 1 (Bmal1), and circadian locomotor output cycles kaput (Clock) mRNA expressions in various neural and peripheral tissues of buntings in different LHSs and discovered differences of ~2 to 6 h in the phase and 2- to 4-fold in amplitude of circadian oscillations of Per2, Cry1, and Bmal1 between photoperiod-induced LHSs. Phase relationship in mRNA oscillations was altered between oscillator components in the circadian pacemaker system (retina, pineal, hypothalamus) as well as in the peripheral (liver, muscle) tissues. These results show for the first time altered waveforms of clock gene expressions in all tissues in parallel with behavioral shifts and suggest the involvement of circadian system in photoperiod induction of seasonal LHSs in a migratory species. [ABSTRACT FROM AUTHOR]

Drosophila melanogaster cryptochrome is one of the model proteins for animal blue-light photoreceptors. Using time-resolved and steady-state optical spectroscopy, we studied the mechanism of light-induced radical-pair formation and decay, and the photoreduction of the FAD cofactor. Exact kinetics on a microsecond to minutes timescale could be extracted for the wild-type protein using global analysis. The wild-type exhibits a fast photoreduction reaction from the oxidized FAD to the FAD•− state with a very positive midpoint potential of ~ +125 mV, although no further reduction could be observed. We could also demonstrate that the terminal tryptophan of the conserved triad, W342, is directly involved in electron transfer; however, photoreduction could not be completely inhibited in a W342F mutant. The investigation of another mutation close to the FAD cofactor, C416N, rather unexpectedly reveals accumulation of a protonated flavin radical on a timescale of several seconds. The obtained data are critically discussed with the ones obtained from another protein, Escherichia coli photolyase, and we conclude that the amino acid opposite N(5) of the isoalloxazine moiety of FAD is able to (de)stabilize the protonated FAD radical but not to significantly modulate the kinetics of any light-inducted reactions. [ABSTRACT FROM AUTHOR]

Cryptochromes are widespread blue-light absorbing flavoproteins with important signaling roles. In plants they mediate de-etiolation, developmental and stress responses resulting from interaction with downstream signaling partners such as transcription factors and components of the proteasome. Recently, it has been shown that Arabidopsis cry1 activation by blue light also results in direct enzymatic conversion of molecular oxygen (O2) to reactive oxygen species ( ROS) and hydrogen peroxide (H2O2) in vitro. Here we explored whether direct enzymatic synthesis of ROS by Arabidopsis cry1 can play a physiological role in vivo., ROS formation resulting from cry1 expression was measured by fluorescence assay in insect cell cultures and in Arabidopsis protoplasts from cryptochrome mutant seedlings. Cell death was determined by colorimetric assay., We found that ROS formation results from cry1 activation and induces cell death in insect cell cultures. In plant protoplasts, cryptochrome activation results in rapid increase in ROS formation and cell death., We conclude that ROS formation by cryptochromes may indeed be of physiological relevance and could represent a novel paradigm for cryptochrome signaling. [ABSTRACT FROM AUTHOR]

The synthesis and functional analysis of KL001 derivatives, which are modulators of the mammalian circadian clock, are described. By using cutting-edge CH activation chemistry, a focused library of KL001 derivatives was rapidly constructed, which enabled the identification of the critical sites on KL001 derivatives that induce a rhythm-changing activity along with the components that trigger opposite modes of action. The first period-shortening molecules that target the cryptochrome (CRY) were thus discovered. Detailed studies on the effects of these compounds on CRY stability implicate the existence of an as yet undiscovered regulatory mechanism. [ABSTRACT FROM AUTHOR]

Although cooperative interactions among kin have been established in a variety of biological systems, their occurrence in plants remains controversial., Plants of Arabidopsis thaliana were grown in rows of either a single or multiple accessions., Plants recognized kin neighbours and horizontally reoriented leaf growth, a response not observed when plants were grown with nonkin. Plant kin recognition involved the perception of the vertical red/far-red light and blue light profiles. Disruption of the light profiles, mutations at the PHYTOCHROME B, CRYPTOCHROME 1 or 2, or PHOTOTROPIN 1 or 2 photoreceptor genes or mutations at the TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS1 gene required for auxin (growth hormone) synthesis impaired the response. The leaf-position response increases plant self-shading, decreases mutual shading between neighbours and increases fitness., Light signals from neighbours are known to shape a more competitive plant body. Here we show that photosensory receptors mediate cooperative rather than competitive interactions among kin neighbours by reducing the competition for local pools of resources. [ABSTRACT FROM AUTHOR]

To serve as a robust internal circadian clock, the cell-autonomous molecular and electrophysiological activities of the individual neurons of the mammalian suprachiasmatic nucleus ( SCN) are coordinated in time and neuroanatomical space. Although the contributions of the chemical and electrical interconnections between neurons are essential to this circuit-level orchestration, the features upon which they operate to confer robustness to the ensemble signal are not known. To address this, we applied several methods to deconstruct the interactions between the spatial and temporal organisation of circadian oscillations in organotypic slices from mice with circadian abnormalities. We studied the SCN of mice lacking Cryptochrome genes ( Cry1 and Cry2), which are essential for cell-autonomous oscillation, and the SCN of mice lacking the vasoactive intestinal peptide receptor 2 (VPAC2-null), which is necessary for circuit-level integration, in order to map biological mechanisms to the revealed oscillatory features. The SCN of wild-type mice showed a strong link between the temporal rhythm of the bioluminescence profiles of PER2:: LUC and regularly repeated spatially organised oscillation. The Cry-null SCN had stable spatial organisation but lacked temporal organisation, whereas in VPAC2-null SCN some specimens exhibited temporal organisation in the absence of spatial organisation. The results indicated that spatial and temporal organisation were separable, that they may have different mechanistic origins (cell-autonomous vs. interneuronal signaling) and that both were necessary to maintain robust and organised circadian rhythms throughout the SCN. This study therefore provided evidence that the coherent emergent properties of the neuronal circuitry, revealed in the spatially organised clusters, were essential to the pacemaking function of the SCN. [ABSTRACT FROM AUTHOR]

Circadian clocks generate daily rhythms in molecular, cellular, and physiological functions providing temporal dimension to organismal homeostasis. Recent evidence suggests two-way relationship between circadian clocks and aging. While disruption of the circadian clock leads to premature aging in animals, there is also age-related dampening of output rhythms such as sleep/wake cycles and hormonal fluctuations. Decay in the oscillations of several clock genes was recently reported in aged fruit flies, but mechanisms underlying these age-related changes are not understood. We report that the circadian light-sensitive protein CRYPTOCHROME ( CRY) is significantly reduced at both m RNA and protein levels in heads of old Drosophila melanogaster. Restoration of CRY using the binary GAL4/ UAS system in old flies significantly enhanced the m RNA oscillatory amplitude of several genes involved in the clock mechanism. Flies with CRY overexpressed in all clock cells maintained strong rest/activity rhythms in constant darkness late in life when rhythms were disrupted in most control flies. We also observed a remarkable extension of healthspan in flies with elevated CRY. Conversely, CRY-deficient mutants showed accelerated functional decline and accumulated greater oxidative damage. Interestingly, overexpression of CRY in central clock neurons alone was not sufficient to restore rest/activity rhythms or extend healthspan. Together, these data suggest novel anti-aging functions of CRY and indicate that peripheral clocks play an active role in delaying behavioral and physiological aging. [ABSTRACT FROM AUTHOR]