Browsing by Subject "ULTRAVIOLET-RADIATION"

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  • Gawronski, Piotr; Burdiak, Pawel; Scharff, Lars B.; Mielecki, Jakub; Gorecka, Magdalena; Zaborowska, Magdalena; Leister, Dario; Waszczak, Cezary; Karpinski, Stanislaw (2021)
    Chloroplast-to-nucleus retrograde signaling is essential for cell function, acclimation to fluctuating environmental conditions, plant growth and development. The vast majority of chloroplast proteins are nuclear-encoded, and must be imported into the organelle after synthesis in the cytoplasm. This import is essential for the development of fully functional chloroplasts. On the other hand, functional chloroplasts act as sensors of environmental changes and can trigger acclimatory responses that influence nuclear gene expression. Signaling via mobile transcription factors (TFs) has been recently recognized as a way of communication between organelles and the nucleus. In this study, we performed a targeted reverse genetic screen to identify dual-localized TFs involved in chloroplast retrograde signaling during stress responses. We found that CHLOROPLAST IMPORT APPARATUS 2 (CIA2) has a functional plastid transit peptide, and can be located both in chloroplasts and the nucleus. Further, we found that CIA2, along with its homolog CIA2-like (CIL) are involved in the regulation of Arabidopsis responses to UV-AB, high light and heat shock. Finally, our results suggest that both CIA2 and CIL are crucial for chloroplast translation. Our results contribute to a deeper understanding of signaling events in the chloroplast-nucleus cross-talk.
  • Mäkelä, Jakke Sakari; Lakkala, Kaisa; Koskela, Tapani; Karppinen, Tomi; Karhu, Juha Matti; Savastiouk, Vladimir; Suokanerva, Hanne; Kaurola, Jussi; Arola, Antti; Lindfors, Anders Vilhelm; Meinander, Outi; De Leeuw, Gerrit; Heikkilä, Anu (2016)
    The data flow involved in a long-term continuous solar spectral UV irradiance monitoring program is investigated and structured to provide an overall view on the multiphase process from data acquisition to the final products. The program employing Brewer spectrophotometers as measuring instruments is maintained by the Finnish Meteorological Institute (FMI) ever since the 1990s at two sites in Finland: Sodankyla (67 degrees N) and Jokioinen (61 degrees N). It is built upon rigorous operation routines, processing procedures, and tools for quality control (QC) and quality analysis (QA) under continuous development and evaluation. Three distinct levels of data emerge, each after certain phase in the data flow: Level 0 denoting raw data, Level 1 meaning calibrated data processed in near-real time, and Level 2 comprising of postprocessed data corrected for all distinguishable errors and known inaccuracies. The final products disseminated to the users are demonstrated to result from a process with a multitude of separate steps, each required in the production of high-quality data on solar UV radiation at the Earth's surface.
  • Geraldes, Vanessa; de Medeiros, Livia Soman; Lima, Stella T.; Alvarenga, Danillo Oliveira; Gacesa, Ranko; Long, Paul F.; Fiore, Marli Fatima; Pinto, Ernani (2020)
    Cyanobacteria have been widely reported to produce a variety of UV-absorbing mycosporine-like amino acids (MAAs). Herein, we reported production of the unusual MAA, mycosporine-glycine-alanine (MGA) in the cyanobacterium Sphaerospermopsis torques-reginae ITEP-024 using a newly developed UHPLC-DAD-MS/HRMS (ultra-high performance liquid chromatography-diode array detection-high resolution tandem mass spectrometry) method. MGA had previously been first identified in a red-algae, but S. torques-reginae strain ITEP-024 is the first cyanobacteria to be reported as an MGA producer. Herein, the chemical structure of MGA is fully elucidated from one-dimensional / two-dimensional nuclear magnetic resonance and HRMS data analyses. MAAs are unusually produced constitutively in S. torques-reginae ITEP-024, and this production was further enhanced following UV-irradiance. It has been proposed that MAA biosynthesis proceeds in cyanobacteria from the pentose phosphate pathway intermediate sedoheptulose 7-phosphate. Annotation of a gene cluster encoded in the genome sequence of S. torques-reginae ITEP-024 supports these gene products could catalyse the biosynthesis of MAAs. However, addition of glyphosate to cultures of S. torques-reginae ITEP-024 abolished constitutive and ultra-violet radiation induced production of MGA, shinorine and porphyra-334. This finding supports involvement of the shikimic acid pathway in the biosynthesis of MAAs by this species.
  • Rantala, Marttiina; Kivila, E. Henriikka; Meyer-Jacob, Carsten; Atti, Sanna; Luoto, Tomi P.; Smol, John P.; Nevalainen, Liisa (2023)
    Algal communities act as sensitive indicators of past and present climate effects on northern lakes, but their responses can vary considerably between ecosystems. Functional trait-based approaches may help us better understand the nature of the diverse biotic responses and their underlying ecosystem changes. We explored patterns in diatom (Bacillariophyceae) growth forms and species composition during the Neoglacial in two shallow lakes typical of subarctic regions, including a dark-colored woodland lake and a clear tundra lake. Sediment carbon and nitrogen elemental and isotope biogeochemistry and spectral indices were used to track broadscale changes in lake productivity, the inflow of organic carbon from land, and benthic substratum over the past three millennia. The biogeochemical indices tracked declines in land-lake connectivity as well as lake-water and sediment organic enrichment above and below the subarctic treeline driven by Neoglacial cooling. This broadscale environmental transition was intercepted by periods of elevated primary production associated with transient Neoglacial warm anomalies and, in particular, the twentieth century warming. Although the Neoglacial development of the lakes showed conspicuous similarities, diatom functional and taxonomic responses were not uniform between the lakes pointing to intrinsic differences in the development of benthic habitats and underwater-light regimes. Many of the observed biotic shifts aligned with expectations based on earlier research linking diatom functional traits to changing light and organic levels but the results also point to further research needs, particularly to better differentiate the individual and interactive effects of substratum and light. Despite distinct anthropogenic imprints in the biogeochemical record, the scale of human impact on the lakes' biota has not, as yet, been profound, but the changes are nonetheless clear when compared to the previous three millennia of natural lake development.
  • Putkinen, Anuliina; Siljanen, Henri M. P.; Laihonen, Antti; Paasisalo, Inga; Porkka, Kaija; Tiirola, Marja; Haikarainen, Iikka; Tenhovirta, Salla; Pihlatie, Mari (2021)
    Methane (CH4) exchange in tree stems and canopies and the processes involved are among the least understood components of the global CH4 cycle. Recent studies have focused on quantifying tree stems as sources of CH4 and understanding abiotic CH4 emissions in plant canopies, with the role of microbial in situ CH4 formation receiving less attention. Moreover, despite initial reports revealing CH4 consumption, studies have not adequately evaluated the potential of microbial CH4 oxidation within trees. In this paper, we discuss the current level of understanding on these processes. Further, we demonstrate the potential of novel metagenomic tools in revealing the involvement of microbes in the CH4 exchange of plants, and particularly in boreal trees. We detected CH4-producing methanogens and novel monooxygenases, potentially involved in CH4 consumption, in coniferous plants. In addition, our field flux measurements from Norway spruce (Picea abies) canopies demonstrate both net CH4 emissions and uptake, giving further evidence that both production and consumption are relevant to the net CH4 exchange. Our findings, together with the emerging diversity of novel CH4-producing microbial groups, strongly suggest microbial analyses should be integrated in the studies aiming to reveal the processes and drivers behind plant CH4 exchange.
  • Glippa, Olivier; Engström-Öst, Jonna; Kanerva, Mirella; Rein, Anni; Vuori, Kristiina (2018)
    On a daily basis, planktonic organisms migrate vertically and thus experience widely varying conditions in their physico-chemical environment. In the Gulf of Finland, these changes are larger than values predicted by climate change scenarios predicted for the next century (up to 0.5 units in pH and 5 degrees C in temperature). In this work, we are interested in how temporal variations in physico-chemical characteristics of the water column on a daily and weekly scale influence oxidative stress level and antioxidant responses in the planktonic copepod of the genus Acartia. Responses were determined from samples collected during a two-week field survey in the western Gulf of Finland, Baltic Sea. Our results showed that GST (Glutathione-S-transferase) enzyme activity increased in the surface waters between Weeks I and II, indicating antioxidant defense mechanism activation. This is most likely due to elevating temperature, pH, and dissolved oxygen observed between these two weeks. During Week II also GSSG (oxidized glutathione) was detected, indicating that copepods responded to stressor(s) in the environment. Our results suggest that Acartia copepods seem fairly tolerant to weekly fluctuations in environmental conditions in coastal and estuarine areas, in terms of antioxidant defense and oxidative stress. This could be directly connected to a very efficient glutathione cycling system acting as antioxidant defense system for neutralizing ROS and avoiding elevated levels of LPX.
  • Pieristè, Marta; Chauvat, Matthieu; Kotilainen, Titta K.; Jones, Alan G.; Aubert, Michaël; Robson, T. Matthew; Forey, Estelle (2019)
    Sunlight can accelerate the decomposition process through an ensemble of direct and indirect processes known as photodegradation. Although photodegradation is widely studied in arid environments, there have been few studies in temperate regions. This experiment investigated how exposure to solar radiation, and specifically UV-B, UV-A, and blue light, affects leaf litter decomposition under a temperate forest canopy in France. For this purpose, we employed custom-made litterbags built using filters that attenuated different regions of the solar spectrum. Litter mass loss and carbon to nitrogen (C:N) ratio of three species: European ash (Fraxinus excelsior), European beech (Fagus sylvatica) and pedunculate oak (Quercus robur), differing in their leaf traits and decomposition rate, were analysed over a period of 7–10 months. Over the entire period, the effect of treatments attenuating blue light and solar UV radiation on leaf litter decomposition was similar to that of our dark treatment, where litter lost 20–30% less mass and had a lower C:N ratio than under the full-spectrum treatment. Moreover, decomposition was affected more by the filter treatment than mesh size, which controlled access by mesofauna. The effect of filter treatment differed among the three species and appeared to depend on litter quality (and especially C:N), producing the greatest effect in recalcitrant litter (F. sylvatica). Even under the reduced irradiance found in the understorey of a temperate forest, UV radiation and blue light remain important in accelerating surface litter decomposition.
  • Rantala, Marttiina V.; Meyer-Jacob, Carsten; Kivila, E. Henriikka; Luoto, Tomi P.; Ojala, Antti. E. K.; Smol, John P.; Nevalainen, Liisa (2021)
    Global environmental change alters the production, terrestrial export, and photodegradation of organic carbon in northern lakes. Sedimentary biogeochemical records can provide a unique means to understand the nature of these changes over long time scales, where observational data fall short. We deployed in situ experiments on two shallow subarctic lakes with contrasting light regimes; a clear tundra lake and a dark woodland lake, to first investigate the photochemical transformation of carbon and nitrogen elemental (C/N ratio) and isotope (delta C-13, delta N-15) composition in lake water particulate organic matter (POM) for downcore inferences. We then explored elemental, isotopic, and spectral (inferred lake water total organic carbon [TOC] and sediment chlorophyll a [CHLa]) fingerprints in the lake sediments to trace changes in aquatic production, terrestrial inputs and photodegradation before and after profound human impacts on the global carbon cycle prompted by industrialization. POM pool in both lakes displayed tentative evidence of UV photoreactivity, reflected as increasing delta C-13 and decreasing C/N values. Through time, the tundra lake sediments traced subtle shifts in primary production, while the woodland lake carried signals of changing terrestrial contributions, indicating shifts in terrestrial carbon export but possibly also photodegradation rates. Under global human impact, both lakes irrespective of their distinct carbon regimes displayed evidence of increased productivity but no conspicuous signs of increased terrestrial influence. Overall, sediment biogeochemistry can integrate a wealth of information on carbon regulation in northern lakes, while our results also point to the importance of considering the entire spectrum of photobiogeochemical fingerprints in sedimentary studies.
  • Puttonen, Maya; Isola, Jorma; Ylinen, Onni; Böhling, Tom; Koljonen, Virve; Sihto, Harri (2022)
    Eccrine porocarcinoma (EPC) is a rare malignant adnexal tumour of the skin. Part of EPCs develop from their benign counterpart, poroma (EP), with chronic light exposure and immunosuppression hypothesized to play a role in the malignant transformation. However, the impact of chronic light exposure on the microenvironment of EPCs and EPs has not been investigated yet. Although the clinical relevance of tumour infiltrating lymphocytes (TILs) and tertiary lymphoid structures (TLSs) has been established in various tumours, their distribution and significance in EPCs and EPs is still poorly understood. We characterized the distribution of TILs and TLSs using CD3, CD4, CD8, CD20 immunohistochemistry in a cohort of 10 EPCs and 49 EPs. We then classified our samples using solar-elastosis grading, analyzing the influence of ultraviolet (UV) damage on TIL density. A negative correlation between UV damage and TIL density was observed (CD4 r = −0.286, p = 0.04. CD8 r = −0.305, p = 0.033). No significant difference in TIL density was found between EPCs and EPs. TLS was scarse with the presence rate 10% in EPCs and 8.3% in EPs. The results suggest that UV has an immunosuppressive effect on the microenvironment of EPCs and EPs.