UV-B Treatment Research Articles

Repressor MrERF4 and Activator MrERF34 Synergistically Regulate High Flavonol Accumulation Under UV-B Irradiation in Morella rubra Leaves.

Flavonols are important plant photoprotectants to defence UV-B irradiation, however, the underlying transcriptional regulatory mechanism of rapid flavonol accumulation in response to UV-B remains unknown. In this study, content of flavonols was significantly induced from 0.11 to 3.80 mg/g fresh weight by UV-B irradiation in leaves of Morella rubra seedlings. MrERF34 was identified as an activator that can regulate the expression of MrFLS2, and promoted flavonol biosynthesis with activator MrMYB12 under UV-B treatment. Transient overexpression of MrERF34 resulted in higher flavonol accumulation, while virus-induced gene silencing of MrERF34 reduced the content of flavonols in bayberry leaves. We further demonstrated that a repressor MrERF4 inhibited the expression of MrERF34 and MrMYB12 as well as MrFLS2 via ERF-associated-amphiphilic repression motif. Exposure to UV-B reduced the promoter activity and transcription of MrERF4, which weakened the inhibitory effect of MrERF4 on MrERF34, MrMYB12, and MrFLS2, leading to a tremendous accumulation of flavonols. Such inhibitory roles of MrERF4 in regulation of flavonol biosynthesis were further validated by transient overexpression in leaves of Nicotiana benthamiana and M. rubra. These findings enrich the synergistical regulatory mechanisms between repressor and activators in flavonol biosynthesis, and provide new insights into photoprotectants biosynthesis to mitigate UV-B stress in plants.

MaPom1, a Dual-Specificity Tyrosine Phosphorylation-Regulated Kinase, Positively Regulates Thermal and UV-B Tolerance in Metarhizium acridum.

Fungi play irreplaceable roles in the functioning of natural ecosystems, but global warming poses a significant threat to them. However, the mechanisms underlying fungal tolerance to thermal and UV-B stresses remain largely unknown. Dual-specificity tyrosine phosphorylation-regulated kinase (DYRK) Pom1 is crucial for fungal growth, conidiation, and virulence. However, its role in stress tolerance within kingdom fungi has not been explored. In this study, we analyzed the function of MaPom1 (a Pom1 homologous gene) in the entomopathogenic fungus Metarhizium acridum and its regulatory roles in stress tolerance. Conidial thermal and UV-B tolerance significantly decreased in the MaPom1 disruption strain (ΔMaPom1), whereas conidial yield and virulence were unaffected. RNA-Seq analysis indicated that the differentially expressed genes (DEGs) were primarily related to amino sugar, nucleotide sugar metabolism, cell wall components, growth and development, and stress response pathways. Under heat shock treatment, the expression levels of heat shock protein genes decreased significantly, leading to reduced thermotolerance. Moreover, under UV-B treatment, MaPom1 expression and the enzyme activity significantly changed, indicating its involvement in regulating UV-B tolerance. The percentage of nuclear damage in ΔMaPom1 under UV-B treatment was higher than that in the wild-type strain (WT) and the complementary strain (CP). Additionally, the transcription levels of DNA damage-related genes significantly decreased, whereas those of several genes involved in the DNA damage repair response increased significantly. Overall, MaPom1 contributed to thermal and UV-B tolerance by regulating the expression of heat shock protein genes and DNA damage repair genes.

Genome-wide identification of the eggplant jasmonate ZIM-domain (JAZ) gene family and functional characterization of SmJAZ10 in modulating chlorophyll synthesis in leaves.

The jasmonate ZIM-domain (JAZ) plays a crucial role in regulating several economic traits in crops. Despite its importance, the characterization of the SmJAZ gene family in eggplant (Solanum melongena L.) has not been documented. In this study, we identified 13 SmJAZ distributed across 9 chromosomes, which were categorized into 5 subgroups based on phylogenetic analysis. Both of them possess TIFY-motif and CCT_2 domains with varying degrees of variation. Promoter cis-element analysis predicted 42 distributed cis-elements that respond to diverse signals. Gene expression analysis demonstrated that SmJAZ exhibited responsiveness to JA, ABA, NaCl, PEG, 4 °C, blue light, and UV-B treatments. Moreover, microRNA interaction predictions identified 150 potential miRNAs, among which ath-miR5021 was found to target 8 SmJAZ mRNAs. Yeast two-hybrid assays demonstrated that most of the SmJAZs were able to interact with SmMYC2 and SmNINJA and could form JAZ-JAZ complexes. Subcellular localization analysis unveiled a diverse array of intranuclear and extranuclear localization signals for SmJAZs. Overexpressing of SmJAZ10 could decrease the chlorophyll content of seedling leaves, and the transcriptome showed that genes related to chlorophyll synthesis, such as SmCHLH, SmPORA, and SmGLK2, underwent down-regulated expression. Overall, these findings serve as a valuable resource for leveraging JA signaling to enhance eggplant quality.

Influence of UV-B and culinary treatment on vitamin D2 and agaritine in button mushrooms

This study investigated the effects of different culinary treatments on the levels of vitamin D2 and agaritine in irradiated white button mushrooms. In addition, the intake of this vitamin via mushroom dishes was evaluated. In fresh irradiated white button mushrooms, the vitamin D2 content was 21.5 ± 2.4 µg/100 g fresh weight, 42 % of which was in the cap skin. The highest losses of vitamin D2 (63 %) were found in samples boiled in acidic water. In contrast, the lowest losses were found in samples boiled in non-acidified water. In the baking and frying experiments, vitamin D2 retention depended more on the cooking time than on the temperature. This resulted in high-heat frying being the second-best treatment for retaining vitamin D2 content in the samples. In the case of agaritine, no effect of UV treatment on its content was observed, and cooking treatment reduced its consumption. At the same time, the formation of toxic degradation products was not observed. The Recommended Daily Intake (RDI) of vitamin D can be achieved by consuming about 75–190 g of cooked, irradiated white button mushrooms, which can thus be an important dietary source of this vitamin.

Light-Regulated Growth, Anatomical, Metabolites Biosynthesis and Transcriptional Changes in Angelica sinensis

Angelica sinensis is an alpine medicinal plant that has been widely used as a general blood tonic and gynecological indications over 2000 years, which depend on the bioactive metabolites (e.g., volatile oils, organic acids, and flavonoids). Although the accumulation of these metabolites is significantly affected by the environmental factors (e.g., altitude, temperature, and sunshine) as found in previous studies, the regulatory mechanism of different lights has not been clearly revealed. Here, growth parameters, contents of bioactive metabolites, and expression levels of related genes were examined when A. sinensis was exposed to different white-light (WL) and UV-B radiation treatments. The results showed that the differences in growth parameters (e.g., plant height, root length, and plant biomass) and leaf tissue characteristics (e.g., leaf thickness, stomatal density and shape, and chloroplast density) were observed under different light treatments. The contents of Z-ligustilide and ferulic acid elevated with the increase of WL (50 to 150 µmol·m2/s) and maximized under the combination of WL-100 and UV-B (107 µW/m2, UV-107) radiation, while the total flavonoids and polysaccharides contents, as well as in vitro antioxidant capacity, elevated with the increasing of WL and UV-B. mRNA transcripts encoding for the biosynthesis of volatile oils, ferulic acid, flavonoids, and polysaccharides were found to be differentially regulated under the different WL and UV-B treatments. These morphological, anatomical, and transcriptional changes are consistent with the elevated bioactive metabolites in A. sinensis under the combination of WL and UV-B. These findings will provide useful references for improving bioactive metabolite production via the cultivation and bioengineering of A. sinensis.

The production of extracellular polymeric substances (EPS) by cyanobacteria isolated from biocrusts in Sejzi Plain, Iran, and their contribution to UVB stress tolerance

ABSTRACT Cyanobacterial extracellular polymeric substances (EPS) are secondary metabolites with high physiological importance for survival under ultraviolet radiation (UVR). This is particularly important in drylands, where cyanobacteria are the main components of biological soil crusts (biocrusts), which are subjected to strong natural solar UVB (280–315 nm) irradiation. This research aims to assess the capability of cyanobacteria isolated from biocrusts from Sejzi Plain, Iran, to produce EPS under UVB treatment. Using a top-down approach, two cyanobacterial species were isolated from biocrusts, and identified as Microcoleus vaginatus and Oscillatoria sp. Both taxa were exposed to controlled UVB radiation for 24, 48 and 72 h. Chlorophyll a content, more soluble EPS fraction (loosely bound EPS, LB-EPS), and less soluble EPS fraction (tightly bound EPS, TB EPS) production were measured. M. vaginatus and Oscillatoria sp. produced equal amounts of both EPS under the UVB treatment. A significant relationship was found for decreasing LB-EPS after 24 h of exposure to UVB, while the amount of TB EPS did not decrease, and even increased significantly after 48 and 72 h. The chlorophyll a content of treated cyanobacteria and their control culture was not significantly different. Therefore, under prolonged UVB up to 72 h, these cyanobacteria produced more TB-EPS than LB-EPS. Consequently, TB-EPS might contribute to higher survival under UVB than LB-EPS.

Multi-Omics Analysis Reveals the Molecular Mechanisms of the Glycolysis and TCA Cycle Pathways in Rhododendron chrysanthum Pall. under UV-B Stress

UV-B radiation is becoming a bigger threat to plants as a result of the ozone layer’s depletion. As an alpine plant, Rhododendron chrysanthum Pall. (R. chrysanthum) may grow regularly under UV-B radiation throughout its lengthy acclimatization period, although the mechanism of acclimatization is still poorly understood. The current investigation uncovered a number of adaptation strategies that R. chrysanthum has developed in reaction to UV-B rays. UV-B radiation impeded photosynthesis and damaged the photosystem, according to OJIP testing. Through transcriptomics and proteomics analyses, this study found that the differential proteins and differential genes of R. chrysanthum were significantly enriched in glycolysis and tricarboxylic acid (TCA) cycle pathways after UV-B treatment. The metabolomics results showed that a total of eight differential metabolites were detected in the glycolytic and TCA cycle pathways, and the changes in the expression of these metabolites reflected the final outcome of gene regulation in the glycolytic and TCA cycle pathways. The combined experimental results demonstrated that R. chrysanthum’s photosynthetic system was impacted by UV-B stress and, concurrently, the plant activated an adaptation mechanism in response to the stress. To maintain its energy supply for growth, R. chrysanthum adapts to UV-B stress by adjusting the expression of the relevant proteins, genes, and metabolites in the glycolytic and TCA cycling pathways. This study provides a new perspective for understanding the changes in the carbon metabolism of R. chrysanthum under UV-B stress and its mechanisms for UV-B resistance, and provides an important theoretical basis for the study of enhancing plant resistance to stress.

Dissecting the genetic basis of UV-B responsive metabolites in rice

BackgroundUV-B, an important environmental factor, has been shown to affect the yield and quality of rice (Oryza sativa) worldwide. However, the molecular mechanisms underlying the response to UV-B stress remain elusive in rice.ResultsWe perform comprehensive metabolic profiling of leaves from 160 diverse rice accessions under UV-B and normal light conditions using a widely targeted metabolomics approach. Our results reveal substantial differences in metabolite accumulation between the two major rice subspecies indica and japonica, especially after UV-B treatment, implying the possible role and mechanism of metabolome changes in subspecies differentiation and the stress response. We next conduct a transcriptome analysis from four representative rice varieties under UV-B stress, revealing genes from amino acid and flavonoid pathways involved in the UV-B response. We further perform a metabolite-based genome-wide association study (mGWAS), which reveals 3307 distinct loci under UV-B stress. Identification and functional validation of candidate genes show that OsMYB44 regulates tryptamine accumulation to mediate UV-B tolerance, while OsUVR8 interacts with OsMYB110 to promote flavonoid accumulation and UV-B tolerance in a coordinated manner. Additionally, haplotype analysis suggests that natural variation of OsUVR8groupA contributes to UV-B resistance in rice.ConclusionsOur study reveals the complex biochemical and genetic foundations that govern the metabolite dynamics underlying the response, tolerance, and adaptive strategies of rice to UV-B stress. These findings provide new insights into the biochemical and genetic basis of the metabolome underlying the crop response, tolerance, and adaptation to UV-B stress.

Characterization of UV-absorbing Mycosporine-like Amino Acids in Freshwater Cyanobacterium Nostoc calcicola

Mycosporine-like amino acids (MAAs) are gaining attention for their UV photoprotective properties and potential applications in biomedical fields, cosmetics, and toiletries. In this study, Nostoc calcicola a genus of cyanobacteria distributed in freshwater were tested for MAA production. This organism was provided by the Freshwater Algae Culture Collection of the Institute of Hydrobiology, the Chinese Academy of Sciences. It was isolated and cultured in the laboratory, in 500 ml glass flasks containing 300 ml of liquid medium BG11 treated on UV-B light 0.1 Wm–2. At different time, cultures were exposed to UV-B light at intensity 0.1 W. m-1 to determine the Maximum PSII photochemical (Fv/Fm). MAAs were extracted using 100% HPLC grade methanol and separated through high-performance liquid chromatography and liquid chromatography/mass spectrometry. Based on liquid chromatography/mass spectrometry analysis, one MAA compound was identified as porphyra. Thus, UV-B treatment of Nostoc calcicola significantly enhanced the production of UV-absorbing mycosporine-like amino acids (MAAs). The content of porphyra could reach up to 8.5 mg/g dry weight in Nostoc calcicola under UV-B treatments for 2 days. The present cyanobacteria could be used for biotechnology research and the UV-absorbing compound porphyra may be of great value in the development of novel sunscreens.

Pityriasis Rubra Pilaris Following Administration of the Pfizer-BioNTech COVID-19 Vaccine Successfully Treated with Acitretin and Dupilumab

Introduction: Pityriasis rubra pilaris (PRP) is an inflammatory eruption of unknown origin; rare cases of COVID-19 vaccine-induced PRP have been reported. Here, we present a case of COVID-19 vaccine-induced pityriasis rubra pilaris inadequately managed with acitretin, successfully treated with the IL-4/IL-13 inhibitor dupilumab. Case Report: A 76-year-old male presented to an outpatient dermatology clinic with a 2-month history of a profoundly pruritic worsening rash characterized by large, orange-salmon-colored follicular papules with scale coalescing into plaques covering approximately 80% of the body surface area. The plaques had well-defined borders and multiple islands of sparing characteristic of PRP. Multiple therapies were trialed with no improvement, including oral prednisone, mycophenolate, topical corticosteroids, antiparasitics, antifungals, doxepin, and UVB treatments. A trial of oral acitretin resulted in improvement of the skin plaques and keratoderma, but the patient remained uncontrollably pruritic. Dupilumab was initiated which provided rapid relief, and the patient has remained clear for several months. Conclusion: Clinicians should be aware of dupilumab’s potential for effective treatment of PRP with recalcitrant pruritus.

Prevention of UVB-Induced Photoaging by an Ethyl Acetate Fraction from Allomyrina dichotoma Larvae and Its Potential Mechanisms in Human Dermal Fibroblasts.

Allomyrina dichotoma larvae (ADL) is an insect type that is used ethnopharmacologically to treat various diseases; however, its use as an antiaging treatment has not been widely studied. Previously, we found that an ethyl acetate (EA) fraction derived from an ADL extract (ADLE) has a high polyphenol content and antioxidant properties. In this study, we identified the underlying molecular mechanism for the protective effect of the EA fraction against UVB-induced photodamage in vitro and ex vivo. UVB treatment increased intracellular reactive oxygen species levels and DNA damage; the latter of which was significantly decreased following cotreatment with the EA fraction. Biological markers of aging, such as p16INK4a, p21WAF1, and senescence-associated β-gal levels, were induced by UVB treatment but significantly suppressed following EA-fraction treatment. UVB-induced upregulation of matrix metalloproteinase (MMP)-1 and downregulation of COL1A1 were also reversed by EA-fraction treatment in both cells and a 3D skin model, which resulted in increased keratin and collagen deposition. Moreover, EA-fraction treatment inhibited the phosphorylation of MAPKs (p38, ERK, and JNK) and nuclear factor (NF-)-kB and decreased the levels of inflammatory cytokines in UVB-treated cells. The results indicate that an EA fraction from ADLE ameliorates UVB-induced degradation of COL1A1 by inhibiting MMP expression and inactivating the MAPK/NF-κB p65/AP-1 signaling pathway involved in this process.

Ultraviolet (Spot)light on Water Treatment: Targeting Inactivation Efficiency and Stress Responses of Gram-Positive and Gram-Negative Bacteria Using UV-B and UV-C LEDs

This study examines the inactivation kinetics and stress responses of Gram-positive and Gram-negative waterborne bacteria using ultraviolet (UV)-B and UV-C LEDs at varying fluences. Our findings show that UV-light-emitting diodes (LED) treatment effectively inactivates both bacterial types, achieving over 4-log reductions at 255 nm and 285 nm wavelengths. Notably, inactivation rates at 285 nm, especially at higher fluences, are comparable to or exceed those at 255 nm. Additionally, UV-B treatment at 285 nm requires shorter exposure times for the same UV dose due to its deeper penetration into water and higher radiant flux. Stress responses varied between species: 255 nm exposure caused more direct DNA damage, triggering the SOS response with recA upregulation, particularly in Gram-positive L. innocua; while 285 nm exposure primarily induced oxidative stress, leading to soxS upregulation, especially in Gram-negative bacteria. These results suggest that UV-B complements UV-C effects by causing reactive oxygen species (ROS) formation in addition to DNA damage, challenging DNA repair. Given the higher cost of UV-C LEDs, our results support the optimization of water treatment systems using UV-B LEDs, which is a promising approach for improving bacterial inactivation while reducing exposure time and energy use.

Effect of UV-B radiation on photosynthesis based flavonoid synthesis in daylily leaves

In order to assess the impact of UV-B radiation on flavonoid compound levels in 'Stella de Oro' daylily leaves, three distinct treatment groups were established: a control group (CK) devoid of UV-B exposure, a low-dose UV-B group (L, 10 μw/cm²), and a high-dose UV-B group (H, 20 μw/cm²). Throughout the UV-B exposure period, parameters including leaf gas exchange, dry weight ratio, and flavonoid compound content were monitored. Following the UV-B treatment, there was a notable increase in the net photosynthesis rate (Pn) by 72 %, stomatal conductance (Gs) by 46 %, transpiration rate (Tr) by 42 %, and water use efficiency (WUE) by 21 %. Moreover, there was a notable increase in the total content of rutin, myricetin, and quercetin in the leaves by 110 %, 55 %, and 47 % respectively. The observed changes in leaf dry weight ratio under UV-B exposure in group H were consistent with the alterations in flavonoid compound levels in the leaves. Based on the results, PCA analysis indicated a significant correlation between WUE and flavonoids content, possibly related with the combined effect of Pn and Tr.

Blueberry (Vaccinium corymbosum L.) postharvest UV-B treatments induce changes in bioactive compounds and reduce weight losses during cold storage

Blueberry (<i>Vaccinium corymbosum</i> L.) postharvest UV-B treatments induce changes in bioactive compounds and reduce weight losses during cold storage

P07 Mutagenicity of narrowband ultraviolet B

Abstract Introduction and aims Exposure to ultraviolet (UV) radiation causes DNA mutations in skin and development of skin cancer. Despite this, UV radiation in the form of narrowband UVB is commonly used by dermatologists to treat skin diseases such as psoriasis. However, the mutagenicity of narrowband UVB in human skin is unknown. In this study, we investigated the mutation burden resulting from a course of narrowband UVB in patients with psoriasis. Methods Skin biopsies were taken from uninvolved skin of sixteen patients with psoriasis before and after a treatment course of narrowband UVB. Following microdissection, DNA was extracted from the epidermis and sequenced using nanorate sequencing (NanoSeq), which detects mutations in single molecules of DNA with an error rate of fewer than five errors per billion base pairs. Whole-genome sequencing of blood DNA was employed as germline control. Comparison of mutations in prenarrowband UVB and postnarrowband UVB skin samples allowed quantification of mutation burden and mutational signatures owing to narrowband UVB. Results There was a significant increase in the mutation burden in skin following the narrowband UVB treatment course, with UV radiation signatures SBS7a, SBS7b and DBS1 documented in both nonsun-exposed skin and frequently sun-exposed skin samples. Comparison of the magnitude of the mutation burden resulting from narrowband UVB to that in keratinocyte cancers provided insight into the mutagenicity of narrowband UVB in relation to the potential numbers of narrowband UVB courses over a lifetime that might lead to skin cancer development. Conclusions Narrowband UVB treatment for psoriasis Results in significant numbers of UV-radiation-induced mutations in human skin.

Weaker photosynthetic acclimation to fluctuating than to corresponding steady UVB radiation treatments in grapevines

AbstractThe effects of transient increases in UVB radiation on plants are not well known; whether cumulative damage dominates or, alternately, an increase in photoprotection and recovery periods ameliorates any negative effects. We investigated photosynthetic capacity and metabolite accumulation of grapevines (Vitis vinifera Cabernet Sauvignon) in response to UVB fluctuations under four treatments: fluctuating UVB (FUV) and steady UVB radiation (SUV) at similar total biologically effective UVB dose (2.12 and 2.23 kJ m−2 day−1), and their two respective no UVB controls. We found a greater decrease in stomatal conductance under SUV than FUV. There was no decrease in maximum yield of photosystem II (Fv/Fm) or its operational efficiency (ɸPSII) under the two UVB treatments, and Fv/Fm was higher under SUV than FUV. Photosynthetic capacity was enhanced under FUV in the light‐limited region of rapid light‐response curves but enhanced by SUV in the light‐saturated region. Flavonol content was similarly increased by both UVB treatments. We conclude that, while both FUV and SUV effectively stimulate acclimation to UVB radiation at realistic doses, FUV confers weaker acclimation than SUV. This implies that recovery periods between transient increases in UVB radiation reduce UVB acclimation, compared to an equivalent dose of UVB provided continuously. Thus, caution is needed in interpreting the findings of experiments using steady UVB radiation treatments to infer effects in natural environments, as the stimulatory effect of steady UVB is greater than that of the equivalent fluctuating UVB.

Development of reversibly photo-crosslinkable water-stable poly(2-ethyl-2-oxazoline) nanofibers via functionalization with cinnamoyl moieties

Poly(2-ethyl-2-oxazoline) (PEtOx) is a potent member of the versatile poly(2-oxazoline) polymer platform with its high hydrophilicity that could be beneficial in numerous biomedical applications, especially in the form of a nanofibrous membrane. However, its water-solubility limits its application in situations where a stable, nanofibrous morphology is required in aqueous environments. The present work offers a straightforward route towards water-stable PEtOx-based nanofibrous membranes, via post-polymerization functionalization with cinnamoyl moieties (PEtOx-Cin) and photo-crosslinking of the electrospun membranes. It is shown that a UVB treatment does not significantly affect the nanofibrous morphology, while successfully inducing the cinnamoyl dimerization process and hence the formation of a polymeric network, as evidenced by spectral analysis. The hereby crosslinked PEtOx-based nanofibers exhibit a prolonged water-stability (at least 45 days), while, interestingly, intermediate irradiation times yield the best results. Full disintegration of the photo-crosslinked nanofibers in aqueous media could be achieved by subsequent UVC exposure. This is not only due to decrosslinking of the cinnamoyl dimers, but was also found to be due to partial degradation of the polymeric backbone. The investigation of UVB/UVC exposure on pure PEtOx nanofibrous membranes confirmed the photo-degradation of the polymeric backbone by a significant decrease in molar mass as observed by size exclusion chromatography and supported by spectral analysis. The hereby proposed, straightforward route for reversible crosslinking of PEtOx-based nanofibrous membranes and their accessible disintegration will contribute to the promotion of these materials in biomedical applications where a water-stable, nanofibrous morphology combined with high hydrophilicity and easy removal is required.

MicroRNA164 Affects Plant Responses to UV Radiation in Perennial Ryegrass.

Increasing the ultraviolet radiation (UV) level, particularly UV-B due to damage to the stratospheric ozone layer by human activities, has huge negative effects on plant and animal metabolism. As a widely grown cool-season forage grass and turfgrass in the world, perennial ryegrass (Lolium perenne) is UV-B-sensitive. To study the effects of miR164, a highly conserved microRNA in plants, on perennial ryegrass under UV stress, both OsmiR164a overexpression (OE164) and target mimicry (MIM164) transgenic perennial ryegrass plants were generated using agrobacterium-mediated transformation, and UV-B treatment (~600 μw cm-2) of 7 days was imposed. Morphological and physiological analysis showed that the miR164 gene affected perennial ryegrass UV tolerance negatively, demonstrated by the more scorching leaves, higher leaf electrolyte leakage, and lower relative water content in OE164 than the WT and MIM164 plants after UV stress. The increased UV sensitivity could be partially due to the reduction in antioxidative capacity and the accumulation of anthocyanins. This study indicated the potential of targeting miR164 and/or its targeted genes for the genetic manipulation of UV responses in forage grasses/turfgrasses; further research to reveal the molecular mechanism underlying how miR164 affects plant UV responses is needed.

Characterization of Mycosporine-like Amino Acids in Chlorophyll f Producing Cyanobacteria from Shaded Niches

Cyanobacteria are the oldest photoautotrophic prokaryotes that can perform plant-like oxygenic photosynthesis. The obligate requirement of sunlight for photosynthesis inevitably exposes cyanobacteria to UV radiation. Mycosporine-like amino acids (MAAs) played necessary roles in protecting cyanobacteria from UV radiation and were frequently reported in cyanobacteria exposed to high light radiation. Here, the MAA production was tried in the chlorophyll f-producing cyanobacterial strains isolated from the shaded environments. Four Chroococcidiopsis strains were finally induced to produce MAAs under 0.15 W·m-2 of UV-B exposure, and the MAA contents increased along with the prolonged UV-B treatments in these four Chroococcidiopsis strains. After separation by HPLC system, one MAA type was detected at similar retention times in the methanol extracts of Chroococcidiopsis strains, and all the MAA compounds showed in-line absorption at 310 nm and mass spectra 246 m/z. The absorption spectra and mass spectra matched well the characteristics of the simplest MAA mycosporine-glycine. Chroococcidiopsis had the simplest MAA gene clusters for mycosporine-glycine. MAAs could also be produced in the cyanobacteria even distributed in the light-deficient niches. These results suggested other roles of MAAs in addition to UV-B protection in the special cyanobacteria from shaded environments.

Interferon alpha promotes caspase-8 dependent ultraviolet light-mediated keratinocyte apoptosis via interferon regulatory factor 1.

Ultraviolet (UV) light is a known trigger of both cutaneous and systemic disease manifestations in lupus patients. Lupus skin has elevated expression of type I interferons (IFNs) that promote increased keratinocyte (KC) death after UV exposure. The mechanisms by which KC cell death is increased by type I IFNs are unknown. Here, we examine the specific cell death pathways that are activated in KCs by type I IFN priming and UVB exposure using a variety of pharmacological and genetic approaches. Mice that overexpress Ifnk in the epidermis were exposed to UVB light and cell death was measured. RNA-sequencing from IFN-treated KCs was analyzed to identify candidate genes for further analysis that could drive enhanced cell death responses after UVB exposure. We identify enhanced activation of caspase-8 dependent apoptosis, but not other cell death pathways, in type I IFN and UVB-exposed KCs. In vivo, overexpression of epidermal Ifnk resulted in increased apoptosis in murine skin after UVB treatment. This increase in KC apoptosis was not dependent on known death ligands but rather dependent on type I IFN-upregulation of interferon regulatory factor 1 (IRF1). These data suggest that enhanced sensitivity to UV light exhibited by lupus patients results from type I IFN priming of KCs that drives IRF1 expression resulting in caspase-8 activation and increased apoptosis after minimal exposures to UVB.