High Levels Of UV-B Radiation Research Articles

Gall-inducing Eriophyes tiliae stimulates the metabolism of Tilia platyphyllos leaves towards oxidative protection

Red galls have high levels of anthocyanins which perform different physiological functions, such as antioxidants and protection against UVB radiation. High levels of anthocyanins and other polyphenols have been associated with low photosynthetic pigment content. In environments with high levels of UVB radiation, it would thus be expected that red galls would have high anthocyanin and polyphenol levels and low photosynthetic pigment contents, enabling the gall with high antioxidant capacity compared to its host organ. The red galls induced by Eriophyes tiliae, and their host environment of Tilia platyphyllos leaves in the Mediterranean climate of Chile, were investigated in relation to their anatomy, histochemistry, pigment, sugar, protein, and polyphenol contents, and antioxidant capacity. The anthocyanin, sugars, and polyphenol contents and the antioxidant capacity were increased in galls. Photosynthetic pigment and protein contents were higher in non-galled leaves. The high levels of anthocyanin and total polyphenols increase the galls' antioxidant capacity in the high UV radiation environment of a Mediterranean climate. The establishment of E. tiliae induced redifferentiation of nutritive tissue, rich in sugars, proteins, and lipids, and an inner epidermis with trichomes and long emergences. E. tiliae galls’ structural and metabolic features are probably enhanced towards mite nutrition and protection. The current results shed light on the role of anthocyanin in the antioxidant protection of plant galls in environments with high UV irradiance.

Olive Varieties under UV-B Stress Show Distinct Responses in Terms of Antioxidant Machinery and Isoform/Activity of RubisCO.

In recent decades, atmospheric pollution led to a progressive reduction of the ozone layer with a consequent increase in UV-B radiation. Despite the high adaptation of olive trees to the Mediterranean environment, the progressive increase of UV-B radiation is a risk factor for olive tree cultivation. It is therefore necessary to understand how high levels of UV-B radiation affect olive plants and to identify olive varieties which are better adapted. In this study we analyzed two Italian olive varieties subjected to chronic UV-B stress. We focused on the effects of UV-B radiation on RubisCO, in terms of quantity, enzymatic activity and isoform composition. In addition, we also analyzed changes in the activity of antioxidant enzymes (SOD, CAT, GPox) to get a comprehensive picture of the antioxidant system. We also evaluated the effects of UV-B on the enzyme sucrose synthase. The overall damage at biochemical level was also assessed by analyzing changes in Hsp70, a protein triggered under stress conditions. The results of this work indicate that the varieties (Giarraffa and Olivastra Seggianese) differ significantly in the use of specific antioxidant defense systems, as well as in the activity and isoform composition of RubisCO. Combined with a different use of sucrose synthase, the overall picture shows that Giarraffa optimized the use of GPox and opted for a targeted choice of RubisCO isoforms, in addition to managing the content of sucrose synthase, thereby saving energy during critical stress points.

Transmission and Prevention of Wuhan Coronavirus Disease 2019 (COVID-19) under Minimum Sunspot Number

Porpoises, infected by Cetacean Morbillivirus from the feces of humpback whales in the East Sea, swam along the Yangtze River to reach Dongting Lake. Infected porpoises could be stranded and moved to Huanan Seafood Wholesale Market. Wuhan is low-lying and susceptible to flooding from the Yangtze River. Agricultural water in Hubei should prevent the harmful algal blooms for clean water. Sterilization by ultraviolet is recommended in air, water and confirmed patient with dialyzer to recover the Wuhan coronavirus disaster. The vaccine can be developed by culturing blood from CeMV infected porpoises in the Yangtze River or Dongting Lake, along with Wuhan coronavirus confirmed patient blood. Existing MMR Vaccine can be applied to cure the confirmed patient. CO2 emissions increased continuously with years (R2= 0.9497) causing high levels of UVB radiation on the Earth. Due to 11 years cycle of the sunspot number, there can be another dangerous outbreak at Dongting Lake with millions of migratory birds in China in coming years between 2030 and 2032.

Differential expression after UV-B radiation and characterization of chalcone synthase from the Patagonian hairgrass Deschampsia antarctica

Deschampsiaantarctica inhabits the maritime territory of Antarctica and South Patagonia. It grows under very harsh environmental conditions. The survival of this species in low freezing temperatures and under high levels of UV-B radiation may constitute some of the most remarkable adaptive plant responses and suggests that this plant possesses genes associated with cold and UV tolerance. Frequently, increased levels of flavonoids have been linked to highly UV-B irradiated plants. Studies examining the biosynthesis of flavonoids in D. antarctica may provide clues to its success in this extreme environment. In this study, we characterized the family of genes encoding chalcone synthase, a key enzyme of the flavonoid biosynthetic pathway. DaCHS was cloned, sequenced and characterized by using software tools. CHS contains two domains, the N-terminal domain ranges from amino acid 8 to 231 and the C-terminal domain ranges from amino acid 241 to 391. Sequence analysis of the three family members revealed a high degree of identity after comparison with other monocotyledons such as Oryza sativa L., Zea mays L. and Hordeum vulgare L. According to these results, DaCHS can be grouped together with H. vulgare CHS1 in the same branch. The phylogenetic tree was built using MEGA software and the neighbour join method with 1000 bootstrap replicates. A model of DaCHS was constructed by way of structural tools and key amino acid residues were identified at the active motif site.

UV-B shock induces photoprotective flavonoids but not antioxidant activity in Antarctic Colobanthus quitensis (Kunth) Bartl

Colobanthus quitensis, the only dicot that inhabits Antarctica, is subjected to different abiotic factors such as high UV-B levels in spring-summer. Several authors described the flavonoid biosynthesis as crucial to tolerating UV-B enriched environments. The goal of this work is the study of the relationship between biosynthesis of flavonoids, resistance to high UV-B levels and the maintenance of redox homeostasis. With this objective, C. quitensis plantlets were subjected to low, medium and high levels of UV-B radiation, in the presence and absence of aminooxiacetic acid (AOA), a phenylalanine ammonia-lyase (PAL) inhibitor with the aim to determine the role of flavonoids in the capacity of C. quitensis to survive to UV-B. The results showed that plants subjected to increasing levels of UV-B, in the absence of the inhibitor, did not present oxidative damage; on the other hand, plants that were treated by the inhibitor showed oxidative stress symptoms and photosynthetical damage. Oxidative damage was correlated with flavonoids content; at the molecular level, these results showed an increase in transcript levels related to the phenylpropanoid pathway enzymes and their activity, as well as the expression of the UVR8−COP1-HY5 transduction system. Moreover, in AOA treated plants, the results show significant damage and plant death. Our results suggest that the survival mechanism showed by C. quitensis to UV-B radiation is mediated by biosynthesis of flavonoids.

Climate change conditions (elevated CO2 and temperature) and UV-B radiation affect grapevine (Vitis vinifera cv. Tempranillo) leaf carbon assimilation, altering fruit ripening rates

The increase in grape berry ripening rates associated to climate change is a growing concern for wine makers as it rises the alcohol content of the wine. The present work studied the combined effects of elevated CO2, temperature and UV-B radiation on leaf physiology and berry ripening rates. Three doses of UV-B: 0, 5.98, 9.66kJm−2d−1, and two CO2–temperature regimes: ambient CO2-24/14°C (day/night) (current situation) and 700ppm CO2-28/18°C (climate change) were imposed to grapevine fruit-bearing cuttings from fruit set to maturity under greenhouse-controlled conditions. Photosynthetic performance was always higher under climate change conditions. High levels of UV-B radiation down regulated carbon fixation rates. A transient recovery took place at veraison, through the accumulation of flavonols and the increase of antioxidant enzyme activities. Interacting effects between UV-B and CO2–temperature regimes were observed for the lipid peroxidation, which suggests that UV-B may contribute to palliate the signs of oxidative damage induced under elevated CO2–temperature. Photosynthetic and ripening rates were correlated. Thereby, the hastening effect of climate change conditions on ripening, associated to higher rates of carbon fixation, was attenuated by UV-B radiation.

Photoprotective and toxicological activities of extracts from the Antarctic moss Sanionia uncinata.

Background:The Antarctic moss Sanionia uncinata (Hedw.) Loeske has shown high ultraviolet (UV)-absorbers content after exposition to high levels of UV-B radiation and can be an important source of antioxidants.Objective:The aim was to investigate photoprotection and mutagenicity by the aqueous extract (AE) and hydroethanolic extract (HE) from the Antarctic moss S. uncinata.Materials and Methods:Photoprotective activities were determined through survival curves of Escherichia coli strains, after UV irradiation in an aqueous solution of thymine and in vitro sun protection factor (SPF). The Salmonella/microsome assays were applied to assess the mutagenicity.Results:Both extracts induced photoprotection against UV-C radiation. The AE showed a higher protection than the hydroethanolic one against UV-induced thymine dimerization. The SPFs were low in both extracts. In association to benzophenone-3 a significant increase in the SPF was detected for the AE, and a significant decrease was induced by the HE. No mutagenicity was found in the both extracts. Furthermore, it was observed absence of cytotoxicity.Conclusion:Water-extractable compounds seem to contribute on photoprotection of this Antarctic moss.

Temperature and UV-B insensitive performance in tadpoles of the Ornate burrowing frog: an ephemeral pond specialist

Animals may overcome the challenges of temperature instability through behavioural and physiological mechanisms in response to short- and long-term temperature changes. When ectotherms face the challenge of large diel temperature fluctuations, one strategy may be to reduce the thermal sensitivity of key traits in order to maintain performance across the range of temperatures experienced. Additional stressors may limit the ability of animals to respond to these thermally challenging environments through changes to energy partitioning or interactive effects. Ornate burrowing frog (Platyplectrum ornatum) tadpoles develop in shallow ephemeral pools that experience high diel thermal variability (>20°C) and can be exposed to high levels of UV-B radiation. Here, we investigated how development in fluctuating versus stable temperature conditions in the presence of high or low UV-B radiation influences thermal tolerance and thermal sensitivity of performance traits of P. ornatum tadpoles. Tadpoles developed in either stable (24°C) or fluctuating temperatures (18-32°C) under high or low UV-B conditions. Tadpoles were tested for upper critical thermal limits, thermal dependence of resting metabolic rate and maximum burst swimming performance. We hypothesised that developmental responses to thermal fluctuations would increase thermal tolerance and reduce thermal dependence of physiological traits, and that trade-offs in the allocation of metabolic resources towards repairing UV-B-induced damage may limit the ability to maintain performance over the full range of temperatures experienced. We found that P. ornatum tadpoles were thermally insensitive for both burst swimming performance, across the range of temperatures tested, and resting metabolic rate at high temperatures independent of developmental conditions. Maintenance of performance led to a trade-off for growth under fluctuating temperatures and UV-B exposure. Temperature treatment and UV-B exposure had an interactive effect on upper critical thermal limits possibly due to the upregulation of the cellular stress response. Thermal independence of key traits may allow P. ornatum tadpoles to maintain performance in the thermal variability inherent in their environment.

Plant physiological responses to UV-B radiation

During the last few decades, there has been considerable concern over the depletion of stratospheric ozone as a result of anthropogenic pollutants. This has resulted in a concomitant increase in solar ultraviolet-B radiation (280–320 nm). High levels of UV-B radiation are responsible for multiple biologically harmful effects in both plants and animals. Many different plant responses to supplemental UV-B radiation have been observed, mostly injurious but sometimes beneficial. UV-B can influence plant processes either through direct damage or via various regulatory effects. In plants, direct effects include DNA damage, membrane changes and protein denaturation, which often cause heritable mutations affecting various physiological processes, including the photosynthetic apparatus. These could adversely affect plant growth, development and morphology, especially the productivity of sensitive crop species. This paper reviews the current knowledge about the plant physiological responses to UV-B stress. doi: http://dx.doi.org/10.9755/ejfa.v24i6.14669

Independent responses to ultraviolet radiation and herbivore attack in broccoli.

The plant responses to ultraviolet-B radiation (UV-B) and to insect herbivory are believed to be partially similar. In this study, responses to these factors were investigated in the crop species broccoli (Brassica oleracea L. convar. botrytis, Brassicaceae). Plants were first grown under three UV-B regimes (80%, 23%, and 4% transmittance of ambient UV-B) in greenhouses covered with either innovative materials (high and medium transmittance) or conventional glass (low transmittance). Half of the plants then remained under these conditions, but the other half were transferred to the field with ambient light and herbivore access for up to 3 d. The plant responses to distinct environmental conditions were examined by analysing the morphological and chemical parameters of plants kept inside and plants exposed in the field. Furthermore, suitability of field-exposed plants to naturally occurring insects was investigated in relation to UV-B pretreatment. High levels of UV-B radiation led to increased flavonoid concentrations, but to a lower biomass accumulation in broccoli. These patterns remained after outdoor exposure. However, UV-induced changes of plant traits did not alter attractiveness to herbivorous insects: thrips, whiteflies, and aphids attacked plants independently of UV-B pretreatment. A 3-fold increase of indolyl glucosinolate concentrations occurred in above-ground tissue of all the plants, most likely due to massive herbivore attack after 3 d of field exposure. The results show that plants respond with high specificity to different abiotic and biotic impacts, demonstrating the separate perception and processing of stress factors.

Effects of prolonged UV-B exposure in plants

Over the past few decades, there has been a depletion of the stratospheric ozone layer due to emissions of halogen-containing compounds of anthropogenic origin. This has resulted in a concomitant increase in solar ultraviolet-B radiation. High levels of UV-B radiation are responsible for multiple biologically harmful effects in both plants and animals. In plants, these effects include DNA damage, which often causes heritable mutations affecting various physiological processes, including the photosynthetic apparatus, protein destruction and signal transduction via UV-B photoreceptors. High UV-B levels introduce a number of different lesions, predominantly cyclobutane pyrimidine dimmers (CPDs) and pyrimidine (6-4) pyrimidinone products [(6-4) PPs] in the genome. These could adversely affect plant growth, development and morphology, especially the productivity of sensitive crop species. This paper reviews the genetic effects of long-term UV-B exposure in plants.

Ultraviolet radiation negatively affects growth but not food quality of arctic diatoms

We studied the short‐term effects of ultraviolet radiation (UV radiation, 280–400 nm) on the fatty acid composition and cellular stoichiometry of three dominant arctic diatom species (Thalassiosira antarctica var. borealis, Chaetoceros socialis, Bacterosira bathyomphala) in laboratory experiments. Photosynthetic efficiency during UV irradiation was inhibited 90%, which led to a substantial reduction in biomass. In contrast to results of previous studies, the percentage of total polyunsaturated fatty acids (PUFAs) did not decrease during UV exposure. Instead, the two major PUFAs, 16:4(n‐1) and 20:5(n‐3), of B. bathyomphala increased, and the PUFA content of T. antarctica and C. socialis did not change significantly. However, the monounsaturated fatty acid 16:1(n‐7) content in all three species substantially decreased during UV radiation. Since high concentrations of 16:1(n‐7) are usually associated with exponential growth under favorable conditions, UV radiation probably did not affect a specific type of fatty acid directly; the fatty acid profile rather reflected a general deterioration in the algal physiological state. The nutritional quality of the fatty acids did not decrease during UV exposure; the C: P and N: P ratios decreased by 50% in all species, whereas the C:N ratios increased slightly in two species. Our results indicate that UV radiation has strong negative effects on photosynthesis and biomass production, but not on food quality with regard to PUFAs and stoichiometry.

Influence of Temperature on the Effects of Artificially Enhanced UV-B Radiation on Aquatic Bryophytes Under Laboratory Conditions

We examined, under laboratory conditions, the influence of temperature (2 °C vs. 10 °C) on the physiological responses of two aquatic bryophytes from a mountain stream to artificially enhanced UV-B radiation for 82 d. These organisms may be exposed naturally to relatively low temperatures and high levels of UV-B radiation, and this combination is believed to increase the adverse effects of UV-B radiation. In the moss Fontinalis antipyretica, UV-B-treated samples showed severe physiological damages, including significant decreases in chlorophyll (Chl) and carotenoid (Car) contents, Chl a/b and Chl/phaeopigment ratios, Chl a fluorescence parameters Fv/Fm and ΦPS2, electron transport rate (ETRmax), and growth. In the liverwort Jungermannia cordifolia, UV-B radiation hardly caused any physiological change except for growth reduction. Thus, this liverwort seemed to be more tolerant to UV-B radiation than the moss under the specific experimental conditions used, maybe partly due to the accumulation of UV-B absorbing compounds. The influence of temperature on the effects of UV-B radiation depended on the species: the higher the UV-B tolerance, the lower the influence of temperature. Also, different physiological variables showed varied responses to this influence. Particularly, the lower temperature used in our study enhanced the adverse effects of UV-B radiation on important physiological variables such as Fv/Fm, growth, and Chl/phaeopigment ratios in the UV-B-sensitive F. antipyretica, but not in the more UV-B-tolerant J. cordifolia. Thus, the adverse effects of cold and UV-B radiation were apparently additive in the moss, but this additiveness was lacking in the liverwort. The Principal Components Analyses (PCA) conducted for both species with the physiological data obtained after 36 and 82 d of culture confirmed the above results. Under natural conditions, the relatively high water temperatures in summer might facilitate the acclimation of aquatic bryophytes from mountain streams to high levels of UV-B radiation. This may be relevant to predict the consequences of concomitant global warming and increasing UV-B radiation.

Caffeine: More Than a Wake-up?

Researchers at Rutgers University conducted an animal study to evaluate topical caffeine's ability to prevent the formation of cutaneous malignancies after high UV light exposure. Hairless laboratory mice were exposed to high levels of UVB radiation (30 mJ/cm2) twice daily for 20 days, producing a …

The Potential Sensitivity of Tropical Plants to Increased Ultraviolet-B Radiation

Little is known concerning the impact of stratospheric ozone depletion and increasing ultraviolet (UV)-B radiation on the phenology and growth of tropical plants. This is because, ostensibly, tropical plants are already exposed to relatively high levels of UV-B radiation (relative to a temperate environment) and should, therefore, possess a greater degree of tolerance to increased UV-B radiation. In this brief review I hope to show that, potentially, direct and indirect effects on photosynthesis, assimilate partitioning, phenology and biomass could occur in both tropical crops (e.g. cassava, rice) and native species (e.g. Cecropia obtusifolia (Bertol. Fl)., Tetramolopium humile (Gray), Nana sandwicensis L.). However, it should be noted that differences in sensitivity to UV-B radiation can be related to experimental conditions, and care should be taken to ensure that the quantity and quality of background solar radiation remains at near ambient conditions. Nevertheless, by integrating current and past studies on the impact of UV-B radiation on tropical species, I hope to be able to demonstrate that photosynthesis, morphology and growth in tropical plants could be directly affected by UV-B radiation and that UV-B radiation may be a factor in species and community dynamics in natural plant populations in the tropics.

Ultraviolet-B Radiation-induced Inhibition of Leaf Expansion and Promotion of Anthocyanin Production

Leaf discs from expanding leaves of Rumex patientia L. were exposed to 7 hours of visible plus different levels of ultraviolet radiation in the 290 to 315 nm waveband (UV-B) and then placed in darkness. Leaf disc expansion was reduced and anthocyanin production was increased in discs exposed to moderate or high levels of UV-B radiation when compared to control discs. The possibility that the inhibition of leaf expansion by UV-B radiation might be at least partially phytochrome-mediated was examined by giving discs brief red or far red irradiation following exposure to UV-B radiation. Brief red radiation (R) following treatment with moderate or high UV-B radiation did not alter the pattern of growth or anthocyanin production compared to discs placed in darkness following UV-B treatment. However, a posttreatment with far red radiation (FR) reduced the growth of discs subjected previously to either moderate UV-B or no UV-B irradiation to the level of growth of discs given high UV-B. FR posttreatment also decreased anthocyanin production in discs in moderate and high UV-B treatments. Effects of FR and UV-B radiation apparently do not involve the same mechanism. This was demonstrated by experiments in which FR following the UV-B treatments was in turn followed by R, which reversed the effects of the FR but did not alter the growth inhibition or increased anthocyanin production induced by moderate or high levels of UV-B radiation.