Long-term variability of human health-related solar ultraviolet-B radiation doses for the 1980s to the end of the 21st century.

Solar ultraviolet-B (UV-B) radiation has played a crucial role in the evolution of life on Earth, and potential changes in its levels could affect the health and functionality of humans and the ecosystems. UV exposure presents both risks and benefits to humans. However, optimal UV-B radiation exposure depends on several environmental and physiological factors and cannot be easily determined. The present document provides a review of the current state of knowledge relative to the effects of UV-B radiation on human health. A brief description of the physical mechanisms that control the levels of solar UV-B radiation at the Earth's surface is provided, with special emphasis on the role of ozone and the importance of the Montreal Protocol. A comprehensive review of studies reporting current trends in levels of surface solar UV-B radiation and projections of future levels reveals the dominant role of climatic changes in the long-term variability of UV-B radiation and its impact on the development of melanomas as well as eye disorders. The review provides strong evidence that despite the success of the Montreal Protocol and the expected ozone recovery, the future evolution of the levels of solar UV-B radiation at the Earth's surface is not certain.

Arabidopsis RUP2 represses UVR8-mediated flowering in noninductive photoperiods.

Plants have evolved complex photoreceptor-controlled mechanisms to sense and respond to seasonal changes in day length. This ability allows plants to optimally time the transition from vegetative growth to flowering. UV-B is an important part intrinsic to sunlight; however, whether and how it affects photoperiodic flowering has remained elusive. Here, we report that, in the presence of UV-B, genetic mutation of REPRESSOR OF UV-B PHOTOMORPHOGENESIS 2 (RUP2) renders the facultative long day plant Arabidopsis thaliana a day-neutral plant and that this phenotype is dependent on the UV RESISTANCE LOCUS 8 (UVR8) UV-B photoreceptor. We provide evidence that the floral repression activity of RUP2 involves direct interaction with CONSTANS, repression of this key activator of flowering, and suppression of FLOWERING LOCUS T transcription. RUP2 therefore functions as an essential repressor of UVR8-mediated induction of flowering under noninductive short day conditions and thus provides a crucial mechanism of photoperiodic flowering control.

Transient impacts of UV-B irradiation on whole body regeneration in a colonial urochordate.

Within the chordates, only some colonial ascidians experience whole body regeneration (WBR), where amputated small colonial fragments containing blood-vessels have the capability to regenerate the entire functional adult zooid within 1-3 weeks. Studying WBR in small colonial fragments taken at different blastogenic stages (the weekly developmental process characteristic to botryllid ascidians) from the ascidian Botrylloides leachii, about half of the fragments were able to complete regeneration (cWBR) three weeks following separation, about half were still in uncomplete, running regeneration (rWBR), and only a small percentage died. cWBR significantly increased in fragments that originated from a late blastogenic stage compared to an early stage. Most B. leachii populations reside in shallow waters, under variable daily natural UV irradiation, and it is of interest to elucidate irradiation effects on development and regeneration. Here, we show that UV-B irradiation resulted in enhanced mortality, with abnormal morphological changes in surviving fragments, yet with non-significant cWBR vs. rWBRs. Further, UV-B irradiation influenced the proportion of blood cells (morula cells, hemoblasts) and of multinucleated cells, a new WBR-associated cell type. At 24-h post-amputation we observed enhanced expression of ß-catenin (a signaling pathway that plays indispensable roles in cell renewal and regeneration), H3 and PCNA in all cell types of non-irradiated as compared to irradiated fragments. These elevated levels were considerably reduced 9-days later. Since WBR is a highly complex phenomenon, the employment of specific experimental conditions, as UV-B irradiation, alongside blastogenesis (the weekly developmental process), elucidates undisclosed facets of this unique biological occurrence such as transient expression of signature genes.

Dissecting the functions of COP1 in the UVR8 pathway with a COP1 variant in Arabidopsis.

COP1 is a critical repressor of plant photomorphogenesis in darkness. However, COP1 plays distinct roles in the photoreceptor UVR8 pathway in Arabidopsis thaliana. COP1 interacts with ultraviolet B (UV-B)-activated UVR8 monomers and promotes their retention and accumulation in the nucleus. Moreover, COP1 has a function in UV-B signaling, which involves the binding of its WD40 domain to UVR8 and HY5 via conserved Val-Pro (VP) motifs of these proteins. UV-B-activated UVR8 interacts with COP1 via both the core domain and the VP motif, leading to the displacement of HY5 from COP1 and HY5 stabilization. However, it remains unclear whether the function of COP1 in UV-B signaling is solely dependent on its VP motif binding capacity and whether UV-B regulates the subcellular localization of COP1. Based on published structures of the COP1 WD40 domain, we generated a COP1 variant with a single amino acid substitution, COP1C509S , which cannot bind to VP motifs but retains the ability to interact with the UVR8 core domain. UV-B only marginally increased nuclear YFP-COP1 levels and significantly promoted YFP-COP1 accumulation in the cytosol, but did not exert the same effects on YFP-COP1C509S . Thus, the full UVR8-COP1 interaction is important for COP1 accumulation in the cytosol. Notably, UV-B signaling including activation of HY5 transcription was obviously inhibited in the Arabidopsis lines expressing YFP-COP1C509S , which cannot bind VP motifs. We conclude that the full binding of UVR8 to COP1 leads to the predominant accumulation of COP1 in the cytosol and that COP1 has an additional function in UV-B signaling besides VP binding-mediated protein destabilization.

ELONGATED HYPOCOTYL5 (HY5) and HY5 HOMOLOGUE (HYH) maintain shade avoidance suppression in UV-B.

Reductions in red to far-red ratio (R:FR) provide plants with an unambiguous signal of vegetational shade and are monitored by phytochrome photoreceptors. Plants integrate this information with other environmental cues to determine the proximity and density of encroaching vegetation. Shade-sensitive species respond to reductions in R:FR by initiating a suite of developmental adaptations termed shade avoidance. These include the elongation of stems to facilitate light foraging. Hypocotyl elongation is driven by increased auxin biosynthesis promoted by PHYTOCHROME INTERACTING FACTORs (PIF) 4, 5 and 7. UV-B perceived by the UV RESISTANCE LOCUS 8 (UVR8) photoreceptor rapidly inhibits shade avoidance, in part by suppressing PIF4/5 transcript accumulation and destabilising PIF4/5 protein. Here, we show that longer-term inhibition of shade avoidance is sustained by ELONGATED HYPOCOTYL 5 (HY5) and HY5 HOMOLOGUE (HYH), which regulate transcriptional reprogramming of genes involved in hormone signalling and cell wall modification. HY5 and HYH are elevated in UV-B and suppress the expression of XYLOGLUCAN ENDOTRANSGLUCOSYLASE/HYDROLASE (XTH) genes involved in cell wall loosening. They additionally increase expression GA2-OXIDASE1 (GA2ox1) and GA2ox2, encoding gibberellin catabolism enzymes that act redundantly to stabilise the PIF-inhibiting DELLA proteins. UVR8 therefore regulates temporally distinct signalling pathways to first rapidly inhibit and subsequently maintain suppression of shade avoidance following UV-B exposure.

UV-B photoreceptor UVR8 interacts with MYB73/MYB77 to regulate auxin responses and lateral root development.

The UV-B photoreceptor UVR8 mediates multiple UV-B responses in plants, but the function of UVR8 in regulating root development has not previously been investigated. Here, we show that UV-B light inhibits Arabidopsis lateral root growth in a UVR8-dependent manner. Monomeric UVR8 inhibits auxin responses in a tissue-autonomous manner and thereby regulates lateral root growth. Genome-wide gene expression analysis demonstrated that auxin and UV-B irradiation antagonistically regulate auxin-regulated gene expression. We further show that UVR8 physically interacts with MYB73/MYB77 (MYB DOMAIN PROTEIN 73/77) in a UV-B-dependent manner. UVR8 inhibits lateral root development via regulation of MYB73/MYB77. When activated by UV-B light, UVR8 localizes to the nucleus and inhibits the DNA-binding activities of MYB73/MYB77 and directly represses the transcription of their target auxin-responsive genes. Our results demonstrate that UV-B light and UVR8 are critical for both shoot morphogenesis and root development. The UV-B-dependent interaction of UVR8 and MYB73/MYB77 serves as an important module that integrates light and auxin signaling and represents a new UVR8 signaling mechanism in plants.

The global distribution of angiosperm genome size is shaped by climate.

Angiosperms, which inhabit diverse environments across all continents, exhibit significant variation in genome sizes, making them an excellent model system for examining hypotheses about the global distribution of genome size. These include the previously proposed large genome constraint, mutational hazard, polyploidy-mediated, and climate-mediated hypotheses. We compiled the largest genome size dataset to date, encompassing 16 017 (> 5% of known) angiosperm species, and analyzed genome size distribution using a comprehensive geographic distribution dataset for all angiosperms. We observed that angiosperms with large range sizes generally had small genomes, supporting the large genome constraint hypothesis. Climate was shown to exert a strong influence on genome size distribution along the global latitudinal gradient, while the frequency of polyploidy and the type of growth form had negligible effects. In contrast to the unimodal patterns along the global latitudinal gradient shown by plant size traits and polyploid proportions, the increase in angiosperm genome size from the equator to 40-50°N/S is probably mediated by different (mostly climatic) mechanisms than the decrease in genome sizes observed from 40 to 50°N northward. Our analysis suggests that the global distribution of genome sizes in angiosperms is mainly shaped by climatically mediated purifying selection, genetic drift, relaxed selection, and environmental filtering.

Unravelling the neglected role of ultraviolet radiation on stomata: A meta-analysis with implications for modelling ecosystem-climate interactions.

Stomata play a pivotal role in regulating gas exchange between plants and the atmosphere controlling water and carbon cycles. Accordingly, we investigated the impact of ultraviolet-B radiation, a neglected environmental factor varying with ongoing global change, on stomatal morphology and function by a Comprehensive Meta-Analysis. The overall UV effect at the leaf level is to decrease stomatal conductance, stomatal aperture and stomatal size, although stomatal density was increased. The significant decline in stomatal conductance is marked (6% in trees and >10% in grasses and herbs) in short-term experiments, with more modest decreases noted in long-term UV studies. Short-term experiments in growth chambers are not representative of long-term field UV effects on stomatal conductance. Important consequences of altered stomatal function are hypothesized. In the short term, UV-mediated stomatal closure may reduce carbon uptake but also water loss through transpiration, thereby alleviating deleterious effects of drought. However, in the long term, complex changes in stomatal aperture, size, and density may reduce the carbon sequestration capacity of plants and increase vegetation and land surface temperatures, potentially exacerbating negative effects of drought and/or heatwaves. Therefore, the expected future strength of carbon sink capacity in high-UV regions is likely overestimated.

Recent advances in UV-B signalling: interaction of proteins with the UVR8 photoreceptor.

The photoreceptor UVR8 mediates many plant responses to UV-B and short wavelength UV-A light. UVR8 functions through interactions with other proteins which lead to extensive changes in gene expression. Interactions with particular proteins determine the nature of the response to UV-B. It is therefore important to understand the molecular basis of these interactions: how are different proteins able to bind to UVR8 and how is differential binding regulated? This concise review highlights recent developments in addressing these questions. Key advances are discussed with regard to: identification of proteins that interact with UVR8; the mechanism of UVR8 accumulation in the nucleus; the photoactivation of UVR8 monomer; the structural basis of interaction between UVR8 and CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) and REPRESSOR OF UV-B PHOTOMORPHOGENESIS (RUP) proteins; the role of UVR8 phosphorylation in modulating interactions and responses to UV-B. Nevertheless, much remains to be understood and the need to extend future research to the growing list of interactors is emphasised.

Different transcription of novel, functional long non-coding RNA genes by UV-B in green algae, Volvox carteri.

Long non-coding RNAs (lncRNAs) are identified as important regulatory molecules related to diverse biological processes. In recent years, benefiting from the rapid development of high-throughput sequencing technology, RNA-seq, and analysis methods, more lncRNAs have been identified and discovered in various plant and algal species. However, so far, only limited studies related to algal lncRNAs are available. Volvox carteri f. nagariensis is the best multicellular model organism to study in developmental and evolutionary biology; therefore, studying and increasing information about this species is important. This study identified lncRNAs in the multicellular green algae Volvox carteri and 1457 lncRNAs were reported, using RNA-seq data and with the help of bioinformatics tools and software. This study investigated the effect of low-dose UV-B radiation on changes in the expression profile of lncRNAs in gonidial and somatic cells. The differential expression of lncRNAs was analyzed between the treatment (UV-B) and the control (WL) groups in gonidial and somatic cells. A total of 37 and 26 lncRNAs with significant differential expression in gonidial and somatic cells, respectively, were reported. Co-expression analysis between the lncRNAs and their neighbor protein-coding genes (in the interval of ± 10 Kb) was accomplished. In gonidial cells, 184 genes with a positive correlation and 13 genes with a negative correlation (greater than 0.95), and in somatic cells, 174 genes with a positive correlation, and 18 genes with a negative correlation were detected. Functional analysis of neighboring coding genes was also performed based on gene ontology. The results of the current work may help gain deeper insight into the regulation of gene expression in the studied model organism, Volvox carteri.

Exploring the complexities of plant UV responses; distinct effects of UV-A and UV-B wavelengths on Arabidopsis rosette morphology.

UV-B radiation can substantially impact plant growth. To study UV-B effects, broadband UV-B tubes are commonly used. Apart from UV-B, such tubes also emit UV-A wavelengths. This study aimed to distinguish effects of different UV-B intensities on Arabidopsis thaliana wildtype and UVR8 mutant rosette morphology, from those by accompanying UV-A. UV-A promotes leaf-blade expansion along the proximal-distal, but not the medio-lateral, axis. Consequent increases in blade length: width ratio are associated with increased light capture. However, petiole length is not affected by UV-A exposure. This scenario is distinct from the shade avoidance driven by low red to far-red ratios, whereby leaf blade elongation is impeded but petiole elongation is promoted. Thus, the UV-A mediated elongation response is phenotypically distinct from classical shade avoidance. UV-B exerts inhibitory effects on petiole length, blade length and leaf area, and these effects are mediated by UVR8. Thus, UV-B antagonises aspects of both UV-A mediated elongation and classical shade avoidance. Indeed, this study shows that accompanying UV-A wavelengths can mask effects of UV-B. This may lead to potential underestimates of the magnitude of the UV-B induced morphological response using broadband UV-B tubes.

Acetylation proteomics and metabolomics analyses reveal the involvement of starch synthase undergoing acetylation modification during UV-B stress resistance in Rhododendron Chrysanthum Pall.

BACKGROUND: Rhododendron chrysanthum Pall. (R. chrysanthum) is a plant that lives in high mountain with strong UV-B radiation, so R. chrysanthum possess resistance to UV-B radiation. The process of stress resistance in plants is closely related to metabolism. Lysine acetylation is an important post-translational modification, and this modification process is involved in a variety of biological processes, and affected the expression of enzymes in metabolic processes. However, little is known about acetylation proteomics during UV-B stress resistance in R. chrysanthum. RESULTS: In this study, R. chrysanthum OJIP curves indicated that UV-B stress damaged the receptor side of the PSII reaction center, with a decrease in photosynthesis, a decrease in sucrose content and an increase in starch content. A total of 807 differentially expressed proteins, 685 differentially acetylated proteins and 945 acetylation sites were identified by quantitative proteomic and acetylation modification histological analysis. According to COG and subcellular location analyses, DEPs with post-translational modification of proteins and carbohydrate metabolism had important roles in resistance to UV-B stress and DEPs were concentrated in chloroplasts. KEGG analyses showed that DEPs were enriched in starch and sucrose metabolic pathways. Analysis of acetylation modification histology showed that the enzymes in the starch and sucrose metabolic pathways underwent acetylation modification and the modification levels were up-regulated. Further analysis showed that only GBSS and SSGBSS changed to DEPs after undergoing acetylation modification. Metabolomics analyses showed that the metabolite content of starch and sucrose metabolism in R. chrysanthum under UV-B stress. CONCLUSIONS: Decreased photosynthesis in R. chrysanthum under UV-B stress, which in turn affects starch and sucrose metabolism. In starch synthesis, GBSS undergoes acetylation modification and the level is upregulated, promotes starch synthesis, making R. chrysanthum resistant to UV-B stress.

A constitutively monomeric UVR8 photoreceptor confers enhanced UV-B photomorphogenesis.

The plant ultraviolet-B (UV-B) photoreceptor UVR8 plays an important role in UV-B acclimation and survival. UV-B absorption by homodimeric UVR8 induces its monomerization and interaction with the E3 ubiquitin ligase COP1, leading ultimately to gene expression changes. UVR8 is inactivated through redimerization, facilitated by RUP1 and RUP2. Here, we describe a semidominant, hyperactive allele, namely uvr8-17D, that harbors a glycine-101 to serine mutation. UVR8G101S overexpression led to weak constitutive photomorphogenesis and extreme UV-B responsiveness. UVR8G101S was observed to be predominantly monomeric in vivo and, once activated by UV-B, was not efficiently inactivated. Analysis of a UVR8 crystal structure containing the G101S mutation revealed the distortion of a loop region normally involved in stabilization of the UVR8 homodimer. Plants expressing a UVR8 variant combining G101S with the previously described W285A mutation exhibited robust constitutive photomorphogenesis. This work provides further insight into UVR8 activation and inactivation mechanisms and describes a genetic tool for the manipulation of photomorphogenic responses.

Identification of One O-Methyltransferase Gene Involved in Methylated Flavonoid Biosynthesis Related to the UV-B Irradiation Response in Euphorbia lathyris.

Flavonoids are ubiquitous polyphenolic compounds that play a vital role in plants' defense response and medicinal efficacy. UV-B radiation is a vital environmental regulator governing flavonoid biosynthesis in plants. Many plants rapidly biosynthesize flavonoids as a response to UV-B stress conditions. Here, we investigated the effects of flavonoid biosynthesis via UV-B irradiation in Euphorbia lathyris. We found that exposure of the E. lathyris callus to UV-B radiation sharply increased the level of one O-methyltransferase (ElOMT1) transcript and led to the biosynthesis of several methylated flavonoids. The methyltransferase ElOMT1 was expressed heterologously in E. coli, and we tested the catalytic activity of recombinant ElOMT1 with possible substrates, including caffeic acid, baicalin, and luteolin, in vitro. ElOMT1 could efficiently methylate when the hydroxyl groups were contained in the core nucleus of the flavonoid. This molecular characterization identifies a methyltransferase responsible for the chemical modification of the core flavonoid structure through methylation and helps reveal the mechanism of methylated flavonoid biosynthesis in Euphorbiaceae. This study identifies the O-methyltransferase that responds to UV-B irradiation and helps shed light on the mechanism of flavonoid biosynthesis in Euphorbia lathyris.

Effects of UV-B Radiation Exposure on Transgenerational Plasticity in Grain Morphology and Proanthocyanidin Content in Yuanyang Red Rice.

The effect of UV-B radiation exposure on transgenerational plasticity, the phenomenon whereby the parental environment influences both the parent's and the offspring's phenotype, is poorly understood. To investigate the impact of exposing successive generations of rice plants to UV-B radiation on seed morphology and proanthocyanidin content, the local traditional rice variety 'Baijiaolaojing' was planted on terraces in Yuanyang county and subjected to enhanced UV-B radiation treatments. The radiation intensity that caused the maximum phenotypic plasticity (7.5 kJ·m-2) was selected for further study, and the rice crops were cultivated for four successive generations. The results show that in the same generation, enhanced UV-B radiation resulted in significant decreases in grain length, grain width, spike weight, and thousand-grain weight, as well as significant increases in empty grain percentage and proanthocyanidin content, compared with crops grown under natural light conditions. Proanthocyanidin content increased as the number of generations of rice exposed to radiation increased, but in generation G3, it decreased, along with the empty grain ratio. At the same time, biomass, tiller number, and thousand-grain weight increased, and rice growth returned to control levels. When the offspring's radiation memory and growth environment did not match, rice growth was negatively affected, and seed proanthocyanidin content was increased to maintain seed activity. The correlation analysis results show that phenylalanine ammonialyase (PAL), cinnamate-4-hydroxylase (C4H), dihydroflavonol 4-reductase (DFR), and 4-coumarate:CoA ligase (4CL) enzyme activity positively influenced proanthocyanidin content. Overall, UV-B radiation affected transgenerational plasticity in seed morphology and proanthocyanidin content, showing that rice was able to adapt to this stressor if previous generations had been continuously exposed to treatment.

Effects of Different Doses of sUV-B Exposure on Taxane Compounds' Metabolism in Taxus wallichiana var. Mairei.

UV-B is an important environmental factor that differentially affects plant growth and secondary metabolites. The effects of supplemental ultraviolet-B (sUV-B) exposure (T1, 1.40 kJ·m-2·day-1; T2, 2.81 kJ·m-2·day-1; and T3, 5.62 kJ·m-2·day-1) on the growth biomass, physiological characteristics, and secondary metabolites were studied. Our results indicated that leaf thickness was significantly (p < 0.05) reduced under T3 relative to the control (natural light exposure, CK); The contents of 6-BA and IAA were significantly reduced (p < 0.05); and the contents of ABA, 10-deacetylbaccatin III, and baccatin III were significantly (p < 0.05) increased under T1 and T2. The paclitaxel content was the highest (0.036 ± 0.0018 mg·g-1) under T3. The cephalomannine content was significantly increased under T1. Hmgr gene expression was upregulated under T1 and T3. The gene expressions of Bapt and Dbtnbt were significantly (p < 0.05) upregulated under sUV-B exposure, and the gene expressions of CoA, Ts, and Dbat were significantly (p < 0.05) downregulated. A correlation analysis showed that the 6-BA content had a significantly (p < 0.05) positive correlation with Dbat gene expression. The IAA content had a significantly (p < 0.05) positive correlation with the gene expression of Hmgr, CoA, Ts, and Dbtnbt. The ABA content had a significantly (p < 0.05) positive correlation with Bapt gene expression. Dbat gene expression had a significantly (p < 0.05) positive correlation with the 10-deacetylbaccatin content. Hmgr gene expression was positively correlated with the contents of baccatin III and cephalomannine. Bapt gene expression had a significantly (p < 0.01) positive correlation with the paclitaxel content. A factor analysis showed that the accumulation of paclitaxel content was promoted under T2, which was helpful in clarifying the accumulation of taxane compounds after sUV-B exposure.

Abscisic Acid Affects Phenolic Acid Content to Increase Tolerance to UV-B Stress in Rhododendron chrysanthum Pall.

The presence of the ozone hole increases the amount of UV radiation reaching a plant's surface, and UV-B radiation is an abiotic stress capable of affecting plant growth. Rhododendron chrysanthum Pall. (R. chrysanthum) grows in alpine regions, where strong UV-B radiation is present, and has been able to adapt to strong UV-B radiation over a long period of evolution. We investigated the response of R. chrysanthum leaves to UV-B radiation using widely targeted metabolomics and transcriptomics. Although phytohormones have been studied for many years in plant growth and development and adaptation to environmental stresses, this paper is innovative in terms of the species studied and the methods used. Using unique species and the latest research methods, this paper was able to add information to this topic for the species R. chrysanthum. We treated R. chrysanthum grown in a simulated alpine environment, with group M receiving no UV-B radiation and groups N and Q (externally applied abscisic acid treatment) receiving UV-B radiation for 2 days (8 h per day). The results of the MN group showed significant changes in phenolic acid accumulation and differential expression of genes related to phenolic acid synthesis in leaves of R. chrysanthum after UV-B radiation. We combined transcriptomics and metabolomics data to map the metabolic regulatory network of phenolic acids under UV-B stress in order to investigate the response of such secondary metabolites to stress. L-phenylalanine, L-tyrosine and phenylpyruvic acid contents in R. chrysanthum were significantly increased after UV-B radiation. Simultaneously, the levels of 3-hydroxyphenylacetic acid, 2-phenylethanol, anthranilate, 2-hydroxycinnamic acid, 3-hydroxycinnamic acid, α-hydroxycinnamic acid and 2-hydroxy-3-phenylpropanoic acid in this pathway were elevated in response to UV-B stress. In contrast, the study in the NQ group found that externally applied abscisic acid (ABA) in R. chrysanthum had greater tolerance to UV-B radiation, and phenolic acid accumulation under the influence of ABA also showed greater differences. The contents of 2-phenylethanol, 1-o-p-coumaroyl-ß-d-glucose, 2-hydroxy-3-phenylpropanoic acid, 3-(4-hydroxyphenyl)-propionic acid and 3-o-feruloylquinic ac-id-o-glucoside were significantly elevated in R. chrysanthum after external application of ABA to protect against UV-B stress. Taken together, these studies of the three groups indicated that ABA can influence phenolic acid production to promote the response of R. chrysanthum to UV-B stress, which provided a theoretical reference for the study of its complex molecular regulatory mechanism.

Inhibiting Neutrophil Extracellular Traps Protects against Ultraviolet B-Induced Skin Damage: Effects of Hochu-ekki-to and DNase I.

UV-B radiation induces sunburn, and neutrophils are pivotal in this inflammation. In this study, we examined the potential involvement of neutrophil extracellular traps (NETs) in ultraviolet B (UVB)-induced skin inflammation, correlating the skin inflammation-mitigating effects of Hochu-ekki-to on UV-B irradiation and NETs. To elucidate NET distribution in the dorsal skin, male ICR mice, exposed to UVB irradiation, were immunohistologically analyzed to detect citrullinated histone H3 (citH3) and peptidylarginine deiminase 4 (PAD4). Reactive oxygen species (ROS) production in the bloodstream was analyzed. To establish the involvement of NET-released DNA in this inflammatory response, mice were UV-B irradiated following the intraperitoneal administration of DNase I. In vitro experiments were performed to scrutinize the impact of Hochu-ekki-to on A23187-induced NETs in neutrophil-like HL-60 cells. UV-B irradiation induced dorsal skin inflammation, coinciding with a significant increase in citH3 and PAD4 expression. Administration of DNase I attenuated UV-B-induced skin inflammation, whereas Hochu-ekki-to administration considerably suppressed the inflammation, correlating with diminished levels of citH3 and PAD4 in the dorsal skin. UV-B irradiation conspicuously augmented ROS and hydrogen peroxide (H2O2) production in the blood. Hochu-ekki-to significantly inhibited ROS and H2O2 generation. In vitro experiments demonstrated that Hochu-ekki-to notably inhibited A23187-induced NETs in differentiated neutrophil-like cells. Hence, NETs have been implicated in UV-B-induced skin inflammation, and their inhibition reduces cutaneous inflammation. Additionally, Hochu-ekki-to mitigated skin inflammation by impeding neutrophil infiltration and NETs in the dorsal skin of mice.

UVR8-TCP4-LOX2 module regulates UV-B tolerance in Arabidopsis.

The phytohormone jasmonate (JA) coordinates stress and growth responses to increase plant survival in unfavorable environments. Although JA can enhance plant UV-B stress tolerance, the mechanisms underlying the interaction of UV-B and JA in this response remain unknown. In this study, we demonstrate that the UV RESISTANCE LOCUS 8 - TEOSINTE BRANCHED1, Cycloidea and PCF 4 - LIPOXYGENASE2 (UVR8-TCP4-LOX2) module regulates UV-B tolerance dependent on JA signaling pathway in Arabidopsis thaliana. We show that the nucleus-localized UVR8 physically interacts with TCP4 to increase the DNA-binding activity of TCP4 and upregulate the JA biosynthesis gene LOX2. Furthermore, UVR8 activates the expression of LOX2 in a TCP4-dependent manner. Our genetic analysis also provides evidence that TCP4 acts downstream of UVR8 and upstream of LOX2 to mediate plant responses to UV-B stress. Our results illustrate that the UV-B-dependent interaction of UVR8 and TCP4 serves as an important UVR8-TCP4-LOX2 module, which integrates UV-B radiation and JA signaling and represents a new UVR8 signaling mechanism in plants.

Does the Symbiotic Relationship Between Hydra Viridissima and Photoautotrophic Alga Provide an Evolutionary Advantage in Protecting DNA against Damage by the Cytotoxic or Genotoxic Mode of Action of Environmental Stressors?

The aim of this paper was to evaluate whether symbiotic cooperation between green hydra (Hydra viridissima) and photoautotrophic alga gives higher resistance of the preservation of DNA integrity compared to brown hydra (Hydra oligactis). Norflurazon concentrations were 0.061 or 0.61 mg/L and UV-B light 254 nm, 0.023mWcm- 2 applied separately or simultaneously. By alkaline comet assay primary DNA damage was assessed and cytotoxicity by fluorescent staining. Norflurazon at 0.61 mg L- 1 significantly increased DNA damage in brown hydras compared to the control (6.17 ± 0.6 µm, 5.2 ± 1.7% vs. 2.9 ± 0.2 µm, 1.2 ± 0.2%). Cytotoxicity was significantly elevated, being higher in brown hydras (25.7 ± 3.5% vs. 8.2 ± 0.2%). UV-B irradiation induced significant DNA damage in brown hydras (13.5 ± 1.0 µm, 4.1 ± 1.0%). Simultaneous exposure to UV-B and norflurazon led to a synergistic DNA damaging. The frequency of cytotoxicity and hedgehog nucleoids was more pronounced in brown (78.3 ± 9.4%; 56.4 ± 6.0%) than in green hydras (34.7 ± 2.5%; 24.2 ± 0.6%). Evolutionary established symbiotic cooperation proved to provide resistance against cyto/genotoxicity.