Presence Of Ultraviolet B Research Articles

Nitric oxide is a key part of the UV-B-induced photomorphogenesis in Arabidopsis

Ultraviolet- B (UV-B) radiation exerts a dual effect on plants. While high doses induce stress, lower doses act as a signal. The sensing of UV-B triggers a photomorphogenic response, causing changes like the hypocotyl shortening. This response is strongly regulated by the UV-B photoreceptor UV RESISTANCE LOCUS 8 (UVR8). Although nitric oxide (NO) was proven to inhibit hypocotyl elongation in Arabidopsis thaliana, its role in UV-B-induced photomorphogenesis remains unclear. By using the NO probe DAF-FM DA, we found that UV-B radiation induced the accumulation of NO in the hypocotyl. This event is dependent on the presence of UVR8. Moreover, the NO donor S-nitrosoglutathione (GSNO), restored the WT phenotype when the Arabidopsis line lacking UVR8 was grown in the presence of UV-B. Also, we found that DELLA proteins were necessary for GSNO sensing in UV-B-induced photomorphogenesis. We showed that, through DELLAs, GSNO negatively controlled the levels of gibberellin (GA) bioprocessing-related genes. Therefore, a downregulation of GA signaling by NO is proposed. On the other hand, GSNO supplementation before UV-B treatment inhibited the induction of genes of the UVR8 signaling pathway: HY5, CHS, and PHR1. This resulted in augmented DNA damage in short exposure to UV-B scenarios. Altogether, these results point to a complex regulation by NO of the UV-B-induced photomorphogenesis.

UV RESISTANCE LOCUS 8-Mediated UV-B Response Is Required Alongside CRYPTOCHROME 1 forPlant Survival in Sunlight under Field Conditions.

As sessile, photoautotrophic organisms, plants are subjected to fluctuating sunlight that includes potentially detrimental ultraviolet-B (UV-B) radiation. Experiments under controlled conditions have shown that the UV-B photoreceptor UV RESISTANCE LOCUS 8 (UVR8) controls acclimation and tolerance to UV-B in Arabidopsis thaliana; however, its long-term impact on plant fitness under naturally fluctuating environments remain poorly understood. Here, we quantified the survival and reproduction of different Arabidopsis mutant genotypes under diverse field and laboratory conditions. We found that uvr8 mutants produced more fruits than wild type when grown in growth chambers under artificial low-UV-B conditions but not under natural field conditions, indicating a fitness cost in the absence of UV-B stress. Importantly, independent double mutants of UVR8 and the blue light photoreceptor gene CRYPTOCHROME 1 (CRY1) in two genetic backgrounds showed a drastic reduction in fitness in the field. Experiments with UV-B attenuation in the field and with supplemental UV-B in growth chambers demonstrated that UV-B caused the cry1 uvr8 conditional lethal phenotype. Using RNA-seq data of field-grown single and double mutants, we explicitly identified genes showing significant statistical interaction of UVR8 and CRY1 mutations in the presence of UV-B in the field. They were enriched in Gene Ontology categories related to oxidative stress, photoprotection and DNA damage repair in addition to UV-B response. Our study demonstrates the functional importance of the UVR8-mediated response across life stages in natura, which is partially redundant with that of cry1. Moreover, these data provide an integral picture of gene expression associated with plant responses under field conditions.

Membrane Blue Dual Protects Retinal Pigment Epithelium Cells/Ganglion Cells-Like through Modulation of Mitochondria Function.

Although recent data highlight the greater protective effects exerted by Membrane Blue Dual (MBD), a precise analysis of the mechanisms of action is missing. We examined the effects of MBD with/without polyethylene glycol (PEG) on both human retinal pigment epithelial cells (ARPE-19) and retinal ganglion cells-like (RGC-5) cultured in the presence/absence of ultraviolet B (UVB) treatment on mitochondria function, oxidants, and apoptosis. In ARPE-19/RGC-5 cells either treated or not with UVB, the effects of MBD with/without PEG were evaluated by specific assays for viability, mitochondrial membrane potential and mitochondrial reactive oxygen species (mitoROS) release. Annexin V was used to detect apoptosis, whereas trypan blue and the scratch assay were used for proliferation/migration. In both physiologic conditions and in the presence of UVB, MBD with/without PEG increased cell viability, mitochondrial membrane potential, proliferation and migration in both ARPE-19 and RGC-5 cells. In general, the effects of MBD with PEG were greater than those caused by MBD without PEG. Our results suggest that, in particular, MBD with PEG is a safe and effective dye for vitreoretinal surgery through the modulation of mitochondrial function.

UV-B Irradiation Effect on Microalgae Performance in the Remediation of Effluent Derived from the Cigarette Butt Cleaning Process.

In this study, the potential of ultraviolet B (UV-B) radiation to alleviate the effects of pollutants in cigarette butt wastewater (CBW) was investigated using different Chlorella sorokiniana strains (F4, R1 and LG1). Microalgae were treated with UV-B (1.7 W m−2) for 3 days prior to their exposure to CBW and then incubated for 4 days in the absence or presence of UV-B. UV-B-untreated microalgae were used as the control. Comparative physiological responses, including photosynthetic pigments and non-enzymatic antioxidants, as well as nicotine and nicotyrine removal, were evaluated in 7-day cultures. UV-B treatments did not negatively impact algal chlorophyll or carotenoid production. UV-B acclimation was strain-dependent, correlating with native environment adaptations and genetic constitutions. UV-B as a pretreatment had long-term positive effects on non-enzymatic antioxidant capacity. However, LG1 needed more time to readjust the pro-oxidant/antioxidant balance, as it was the most UV-B-sensitive. Phenolic compounds played an important role in the antioxidant system response to UV-B, while flavonoids did not contribute to the total antioxidant capacity. Although cross-resistance between UV-B and CBW was observed in F4 and R1, only R1 showed nicotine/nicotyrine catabolism induction due to UV-B. Overall, the results suggest that UV-B activates defense pathways associated with resistance or tolerance to nicotine and nicotyrine.

Antioxidant activity of kafirin hydrolysates on UVB irradiated human keratinocyte cells and in silico identification.

Ultraviolet B (UVB) causes photoaging of the skin, the appearance of wrinkles, spots, and alteration of the skin barrier. The main cells in the most superficial layer of the skin are the keratinocytes; these cells play an important role in protecting this organ. The present study aimed to investigate the antioxidant activity of the hydrolysates from kafirin to inhibit UVB-induced responses in human keratinocytes cells (HaCaT). Kafirin hydrolysates were produced by enzymatic hydrolysis with alcalase. The activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), in the HaCaT cell line in the presence of UVB and the effects of the hydrolysates against the UVB-induced response were evaluated. Furthermore, the peptides that were generated by hydrolysis were identified in silico using the BIOPEP database. Two protein sequences were identified (α-kafirin and the precursor protein of α-kafirin), in the kafirin extract. A degree of hydrolysis of 18.8% was obtained by hydrolyzing the kafirin extract with alcalase. The kafirin hydrolysates avoided the decrease in endogenous antioxidant enzymes such as SOD, CAT, and GPx reducing the oxidative stress generated by UVB. Using the BIOPEP-UWM database, we found 102 peptide sequences, and it has shown that the peptides have a large amount of hydrophobic amino acids such as proline, alanine, and glutamine, and amino acids with high antioxidant capacity. These results suggest that the kafirin hydrolysates can be used as antioxidant agents to ameliorate UVB-induced skin keratinocytes cells' response in vitro, providing an alternative against UVB-induced photoaging.

GCR1 Positively Regulates UV-B- and Ethylene-Induced Stomatal Closure via Activating GPA1-Dependent ROS and NO Production.

Heterotrimeric G proteins function as key players in guard cell signaling to many stimuli, including ultraviolet B (UV-B) and ethylene, but whether guard cell G protein signaling is activated by the only one potential G protein-coupled receptor, GCR1, is still unclear. Here, we found that gcr1 null mutants showed defects in UV-B- and ethylene-induced stomatal closure and production of reactive oxygen species (ROS) and nitric oxide (NO) in guard cells, but these defects could be rescued by the application of a Gα activator or overexpression of a constitutively active form of Gα subunit GPA1 (cGPA1). Moreover, the exogenous application of hydrogen peroxide (H2O2) or NO triggered stomatal closure in gcr1 mutants and cGPA1 transgenic plants in the absence or presence of UV-B or ethylene, but exogenous ethylene could not rescue the defect of gcr1 mutants in UV-B-induced stomatal closure, and gcr1 mutants did not affect UV-B-induced ethylene production in Arabidopsis leaves. These results indicate that GCR1 positively controls UV-B- and ethylene-induced stomatal closure by activating GPA1-dependent ROS and NO production in guard cells and that ethylene acts upstream of GCR1 to transduce UV-B guard cell signaling, which establishes the existence of a classic paradigm of G protein signaling in guard cell signaling to UV-B and ethylene.

UV RESISTANCE LOCUS8 mediates ultraviolet-B-induced stomatal closure in an ethylene-dependent manner

Although the UV RESISTANCE LOCUS 8 (UVR8)-CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1)-ELONGATED HYPOCOTYL5 (HY5) signaling pathway, ethylene, hydrogen peroxide (H2O2), and nitric oxide (NO) all participate in ultraviolet-B (UV-B)-triggered stomatal closing, their interrelationship is not clear. Here, we found that UV-B-induced the expression of ethylene biosynthetic genes, production of ethylene, H2O2, and NO, and stomata closing were impaired in uvr8, cop1, and hy5 mutants. UV-B-induced NO production and stomata closing were also defective in mutants for ETHYLENE RESPONSE 1 (ETR1), ETHYLENE INSENSITIVE 2 (EIN2), and EIN3, but UV-B-triggered H2O2 generation was only inhibited in etr1. In either the absence or presence of UV-B, ethylene triggered H2O2 production but not NO generation and stomatal closure in cop1 and hy5, and stomata closing in cop1 and hy5 was induced by NO but not H2O2. Moreover, NO production and stomatal closure were constitutively caused by over-expression of COP1 or HY5 in ein2 and ein3, but not by over-expression of EIN2 or EIN3 in cop1 and hy5. Our data indicate that the UVR8-COP1-HY5 signaling module mediates UV-B-induced ethylene production, ethylene is then perceived by ETR1 to induce H2O2 synthesis. H2O2 induces NO generation and subsequent stomata closing via an EIN2, EIN3, COP1, and HY5-dependent pathway(s).

The inhibition of NOTCH2 reduces UVB-induced damage in retinal pigment epithelium cells.

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the elderly. The pathogenesis of dry AMD remains indistinct and the mechanism of retinal pigment epithelium (RPE) cells death in dry AMD is controversial. The aim of the present study was to investigate the functions of Notch signaling in ultraviolet B (UVB)-induced damage of RPE cells. It was identified that, in RPE cells, UVB increased intracellular reactive oxygen species (ROS) and induced cell apoptosis. In addition, UVB activated Notch signaling in a dose dependent manner. Surprisingly, NOTCH2, but not NOTCH1, was demonstrated to be the major Notch receptor in RPE cells. Under normal conditions, the inhibition of NOTCH2 reduced cell growth and cell migration, but had no impact on intracellular ROS and cell apoptosis. However, in the presence of UVB, the inhibition of NOTCH2, but not NOTCH1, attenuated intracellular ROS and cell apoptosis. The function of Notch signaling involved in UVB damage of RPE cells may not only be significant to understanding the pathogenesis of AMD (especially dry AMD), but also useful for designing effective therapeutic agents for dry AMD.

Ultraviolet B radiation alters movement and thermal selection of zebrafish (Danio rerio).

Temperature and ultraviolet B (UV-B) interact in causing cellular damage and impairing locomotor performance. Here, we test the hypothesis that movement and thermal selection of zebrafish (Danio rerio) change in the presence of UV-B, and in particular, that fish which were chronically exposed to UV-B avoid high and low temperature extremes to maximize activities of antioxidant enzymes. Fish chronically (two to three weeks) exposed to UV-B had increased reactive oxygen species (ROS)-induced damage to proteins and membranes, and reduced swimming performance at high (more than 26°C) temperatures. In an open field arena with a thermal gradient, chronically exposed fish avoided high and low temperature extremes compared with control fish. Additionally, both control and chronically exposed fish showed slower voluntary swimming speeds in the presence of UV-B. We suggest that in the presence of UV-B fish may reduce muscular activity to minimize intrinsic ROS production. Our data show that the interaction between UV-B and temperature determines movement and microhabitat selection of fish, which is therefore of ecological importance particularly in anthropogenically modified environments.

Ultraviolet-B radiation stimulates downward leaf curling in Arabidopsis thaliana

Plants are very well adapted to growth in ultraviolet-B (UV-B) containing light. In Arabidopsis thaliana, many of these adaptations are mediated by the UV-B receptor UV RESISTANCE LOCUS 8 (UVR8). Using small amounts of supplementary UV-B light, we observed changes in the shape of rosette leaf blades. Wild type plants show more pronounced epinasty of the blade edges, while this is not the case in uvr8 mutant plants. The UVR8 effect thus mimics the effect of phytochrome (phy) B in red light. In addition, a meta-analysis of transcriptome data indicates that the UVR8 and phyB signaling pathways have over 70% of gene regulation in common. Moreover, in low levels of supplementary UV-B light, mutant analysis revealed that phyB signaling is necessary for epinasty of the blade edges. Analysis of auxin levels and the auxin signal reporter DR5::GUS suggest that the epinasty relies on altered auxin distribution, keeping auxin at the leaf blade edges in the presence of UV-B. Together, our results suggest a co-action of phyB and UVR8 signaling, with auxin as a downstream factor.

UVR8 in Arabidopsis thaliana regulates multiple aspects of cellular differentiation during leaf development in response to ultraviolet B radiation

Responses specific to ultraviolet B (UV-B) wavelengths are still poorly understood, both in terms of initial signalling and effects on morphogenesis. Arabidopsis thaliana UV RESISTANCE LOCUS8 (UVR8) is the only known UV-B specific signalling component, but the role of UVR8 in leaf morphogenesis is unknown. The regulatory effects of UVR8 on leaf morphogenesis at a range of supplementary UV-B doses were characterized, revealing both UVR8-dependent and independent responses to UV irradiation. Inhibition of epidermal cell division in response to UV-B is largely independent of UVR8. However, overall leaf growth under UV-B irradiation in wild-type plants is enhanced compared with a uvr8 mutant because of a UVR8-dependent compensatory increase of cell area in wild-type plants. UVR8 was also required for the regulation of endopolyploidy in response to UV-B, and the uvr8 mutant also has a lower density of stomata than the wild type in the presence of UV-B, indicating that UVR8 has a regulatory role in other developmental events. Our findings show that, in addition to regulating UV-protective gene expression responses, UVR8 is involved in controlling aspects of leaf growth and morphogenesis. This work extends our understanding of how UV-B response is orchestrated at the whole-plant level.

Effects of ultraviolet-B radiation on behaviour and growth of three species of amphibian larvae

Effects of ultraviolet-B (UV-B) radiation on amphibian embryos have been investigated in a number of studies, but the effects on larvae have received less attention. We investigated the effects of UV-B radiation on the behaviour and growth of larvae of three amphibians ( Rana arvalis, Rana temporaria and Bufo bufo) in two different experiments. First, we tested whether larvae of the three species actively avoid UV-B exposure if given a choice. We found no evidence for active avoidance of UV-B or changes in activity in the presence of UV-B in any of the species. Second, we assessed the effects of natural (1.25 kJ m −2) and enhanced (1.58 kJ m −2) UV-B radiation on the survival and growth of the three species and found that the exposure to UV-B radiation did not have any effect on survival rates of any of the species. However, UV-B radiation had a positive effect on the growth of R. arvalis and R. temporaria, whereas the growth of B. bufo tadpoles was unaffected by the UV-B treatments. Our results suggest that a short-term exposure to UV-B radiation does not induce any UV-B avoidance behaviour in tadpoles of these three species. Furthermore, unlike some previous studies, the results suggest that the young tadpoles of these species are not negatively affected by UV-B radiation. In fact, our results demonstrate that a moderate amount of UV-B radiation enhance tadpole growth rates in two of the three species.