UV-B Responses Research Articles

High-glucose impact on UVB responses in human epidermal keratinocytes: Insights on diabetic skin's resistance to photocarcinogenesis

Ultraviolet (UV) B-induced damage in human epidermal keratinocytes (HEKs) initiates photocarcinogenesis. However, how diabetes influences photocarcinogenesis is not well understood. To investigate the impact of high-glucose environments on responses to UVB, we cultured HEKs in normal-glucose (NG) or high-glucose (HG) conditions (G6 and G26), followed by UVB irradiation at 25 mJ/cm2 (G6UVB and G26UVB). We performed next-generation sequencing and analyzed HEKs' expression profiles bioinformatically to identify candidate genes and cellular responses involved. We found UVB induced consistent responses in both NG- and HG-cultivated HEKs, but it also triggered certain distinct processes and pathways specifically in the HG groups. The 459 differentially expressed (DE) genes in the HG groups revealed their roles in chromatin remodeling, nucleosome assembly, and interferon signaling activation. Moreover, the 29 DE genes identified in G26UVB/G6UVB comparison, including the potent tumor suppressor gene TFPI2, were considered key genes contributing to HEKs' altered response to UVB in HG environments. UVB irradiation induced significantly higher TFPI2 expression in HG-cultivated HEKs than their NG-cultivated counterpart. Finally, HG-cultivation significantly increased oxidative stress, cyclobutane pyrimidine dimer formation, and apoptosis, while reducing HEKs' viability after UVB irradiation. These changes under HG conditions probably mediate cell fate toward death and tumor regression. Overall, our findings provide evidence and associated molecular basis on how HG conditions reduce keratinocytes' photocarcinogenic potential following UVB exposure.

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.

Genomic data provides insights into the evolutionary history and adaptive differentiation of two tetraploid strawberries.

Over the decades, evolutionists and ecologists have shown intense interest in the role of polyploidization in plant evolution. Without clear knowledge of the diploid ancestor(s) of polyploids, we would not be able to answer fundamental ecological questions such as the evolution of niche differences between them or its underlying genetic basis. Here, we explored the evolutionary history of two Fragaria tetraploids, Fragaria corymbosa and Fragaria moupinensis. We de novo assembled five genomes including these two tetraploids and three diploid relatives. Based on multiple lines of evidence, we found no evidence of subgenomes in either of the two tetraploids, suggesting autopolyploid origins. We determined that Fragaria chinensis was the diploid ancestor of F. corymbosa while either an extinct species affinitive to F. chinensis or an unsampled population of F. chinensis could be the progenitor of F. moupinensis. Meanwhile, we found introgression signals between F. chinensis and Fragaria pentaphylla, leading to the genomic similarity between these two diploids. Compared to F. chinensis, gene families related to high ultraviolet (UV)-B and DNA repair were expanded, while those that responded towards abiotic and biotic stresses (such as salt stress, wounding, and various pathogens) were contracted in both tetraploids. Furthermore, the two tetraploids tended to down-regulate defense response genes but up-regulate UV-B response, DNA repairing, and cell division gene expression compared to F. chinensis. These findings may reflect adaptions toward high-altitude habitats. In summary, our work provides insights into the genome evolution of wild Fragaria tetraploids and opens up an avenue for future works to answer deeper evolutionary and ecological questions regarding the strawberry genus.

OsUVR8b, rather than OsUVR8a, plays a predominant role in rice UVR8-mediated UV-B response.

UV RESISTANCE LOCUS 8 (UVR8) has been identified in Arabidopsis thaliana as the receptor mediating responses to UV-B radiation. However, UVR8-mediated UV-B signaling pathways in rice, which possesses two proteins (UVR8a and UVR8b) with high identities to AtUVR8, remain largely unknown. Here, UVR8a/b were found to be predominantly expressed in rice leaves and leaf sheaths, while the levels of UVR8b transcript and UVR8b protein were both higher than those of UVR8a. Compared to wild-type (WT) plants, uvr8b and uvr8a uvr8b rice mutants exposed to UV-B showed reduced UV-B-induced growth inhibition and upregulation of CHS and HY5 transcripts alongside UV-B acclimation. However, uvr8a mutant was similar to WT plants and exhibited changes comparable with WT. Overexpressing OsUVR8a/b enhanced UV-B-induced growth inhibition and acclimation to UV-B. UV-B was able to enhance the interaction between E3 ubiquitin ligase OsCOP1 and OsUVR8a/b, whereas the interaction of the homologous protein of Arabidopsis REPRESSOR OF UV-B PHOTOMORPHOGENESIS2 (AtRUP2) in rice with OsUVR8a/b was independent of UV-B. Additionally, OsUVR8a/b proteins were also found in the nucleus and cytoplasm even in the absence of UV-B. The abundance of OsUVR8 monomer showed an invisible change in the leaves of rice seedlings transferred from white light to that supplemented with UV-B, even though UV-B was able to weaken the interactions between OsUVR8a and OsUVR8b homo and heterodimers. Therefore, both OsUVR8a and OsUVR8b, which have different localization and response patterns compared with AtUVR8, function in the response of rice to UV-B radiation, whereas OsUVR8b plays a predominant role in this process.

A synchronized, large-scale field experiment using Arabidopsis thaliana reveals the significance of the UV-B photoreceptor UVR8 under natural conditions.

This study determines the functional role of the plant ultraviolet-B radiation (UV-B) photoreceptor, UV RESISTANCE LOCUS 8 (UVR8) under natural conditions using a large-scale 'synchronized-genetic-perturbation-field-experiment'. Laboratory experiments have demonstrated a role for UVR8 in UV-B responses but do not reflect the complexity of outdoor conditions where 'genotype × environment' interactions can mask laboratory-observed responses. Arabidopsis thaliana knockout mutant, uvr8-7, and the corresponding Wassilewskija wild type, were sown outdoors on the same date at 21 locations across Europe, ranging from 39°N to 67°N latitude. Growth and climatic data were monitored until bolting. At the onset of bolting, rosette size, dry weight, and phenolics and glucosinolates were quantified. The uvr8-7 mutant developed a larger rosette and contained less kaempferol glycosides, quercetin glycosides and hydroxycinnamic acid derivatives than the wild type across all locations, demonstrating a role for UVR8 under field conditions. UV effects on rosette size and kaempferol glycoside content were UVR8 dependent, but independent of latitude. In contrast, differences between wild type and uvr8-7 in total quercetin glycosides, and the quercetin-to-kaempferol ratio decreased with increasing latitude, that is, a more variable UV response. Thus, the large-scale synchronized approach applied demonstrates a location-dependent functional role of UVR8 under natural conditions.

Unveiling UVB resilience in Oryza sativa L.: Integrative analysis of physiological, molecular and microRNA responses

Rice is the staple food for more than half of the global population. It is cultivated in over 100 countries, and is predominant in Asia, which accounts for 90 % of the world's production. As the most crucial food crop globally, rice is sensitive to both UVB radiation and climate variations. UltraViolet-B radiation (UVB) is recognised as adverse factors for photosynthesis and plant growth. The current study investigates the resilience of Oryza sativa L. (IR20) seedlings to UVB irradiation, focusing on parameters such as photosynthetic pigment, total sugar, phenolic, total free amino acids, malondialdehyde content, hydrogen peroxide, and antioxidative enzymes. The mRNA expression levels of genes involved in UVB perception, signalling, and response (UVR8, HY5, RLCK, PHT2, and URP) were studied using quantitative RT-PCR (RT-qPCR). Additionally, a computational approach was employed to identify UVB-responsive microRNAs (miRNAs) and their corresponding target mRNAs; which were subsequently validated using stem-loop RT-qPCR and RT-qPCR, respectively. Surprisingly, it was discovered that the H2O2 content in the IR20 cultivar increased in response to UVB irradiation, despite no significant changes observed in lipid peroxidation, chlorophyll, and phenolic content. Additionally, UVB irradiation increases the total sugar content and decreases the entire free amino acid content, while not affecting total protein. The RT-qPCR analysis of mRNA expression reveals that UVB exposure augment the expression of genes related to UVB signal detection (UVR8), signalling (HY5, RLCK, and WRKY), and response (PHT2, CA, and URP). Our findings also suggest that at the post-transcriptional stage, miRNAs expressed upon UVB irradiation are responsible for the significant tolerance of IR20 seedlings to UVB radiation. Overall, the results reveal that IR20 exhibits promise candidate for the development of rice varieties that are both highly productive and resilient to UVB induced stress.

Changes in Physiological Indices, Amino Acids, and Volatile Compounds in Vitis vinifera L. cv. Pinot Noir under UV-B Radiation and Water Deficit Conditions.

UV-B radiation and water deficit can challenge Pinot noir growth and fruit quality. The aim of this work is to determine the effects of UV-B and water deficit on the physiological indices, amino acids, and volatile compounds of Pinot noir vine and fruit. The results showed that both individual and combined treatments caused a decrease in the leaf SPAD, with the largest amplitude being observed in the combined treatment. Water deficit also decreased the leaf water potential and increased the juice δ13C‱ at harvest, which was the opposite of the latter under UV-B radiation. Interestingly, most of the physiological indices under combined stresses did not show significant changes compared with that under no UV-B and the well-watered control treatment. Moreover, the concentrations of amino acids and volatile compounds in the berries were determined at harvest. The amino acid contents were significantly increased by the combined treatment, particularly proline (Pro), aspartate (Arg), alanine (Ala), and threonine (Thr). There were slight increases in volatile compounds. This research substantially contributed to improve our scientific understanding of UV-B and water deficit responses in an important commercial species. In addition, it highlighted some future research to produce high-quality wines with the anticipated specific characteristics.

Rhododendron chrysanthum's Primary Metabolites Are Converted to Phenolics More Quickly When Exposed to UV-B Radiation.

The plant defense system is immediately triggered by UV-B irradiation, particularly the production of metabolites and enzymes involved in the UV-B response. Although substantial research on UV-B-related molecular responses in Arabidopsis has been conducted, comparatively few studies have examined the precise consequences of direct UV-B treatment on R. chrysanthum. The ultra-high-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) methodology and TMT quantitative proteomics are used in this study to describe the metabolic response of R. chrysanthum to UV-B radiation and annotate the response mechanism of the primary metabolism and phenolic metabolism of R. chrysanthum. The outcomes demonstrated that following UV-B radiation, the primary metabolites (L-phenylalanine and D-lactose*) underwent considerable changes to varying degrees. This gives a solid theoretical foundation for investigating the use of precursor substances, such as phenylalanine, to aid plants in overcoming abiotic stressors. The external application of ABA produced a considerable increase in the phenolic content and improved the plants' resistance to UV-B damage. Our hypothesis is that externally applied ABA may work in concert with UV-B to facilitate the transformation of primary metabolites into phenolic compounds. This hypothesis offers a framework for investigating how ABA can increase a plant's phenolic content in order to help the plant withstand abiotic stressors. Overall, this study revealed alterations and mechanisms of primary and secondary metabolic strategies in response to UV-B radiation.

UV-B responses in the spotlight: Dynamic photoreceptor interplay and cell-type specificity.

Plants are constantly exposed to a multitude of external signals, including light. The information contained within the full spectrum of light is perceived by a battery of photoreceptors, each with specific and shared signalling outputs. Recently, it has become clear that UV-B radiation is a vital component of the electromagnetic spectrum, guiding growth and being crucial for plant fitness. However, given the large overlap between UV-B specific signalling pathways and other photoreceptors, understanding how plants can distinguish UV-B specific signals from other light components deserves more scrutiny. With recent evidence, we propose that UV-B signalling and other light signalling pathways occur within distinct tissues and cell-types and that the contribution of each pathway depends on the type of response and the developmental stage of the plant. Elucidating the precise site(s) of action of each molecular player within these signalling pathways is key to fully understand how plants are able to orchestrate coordinated responses to light within the whole plant body. Focusing our efforts on the molecular study of light signal interactions to understand plant growth in natural environments in a cell-type specific manner will be a next step in the field of photobiology.

Genome-Wide Identification and Expression Analysis of RCC1 Gene Family under Abiotic Stresses in Rice (Oryza sativa L.)

In plants, the essential roles played by the regulator of chromosome condensation 1 (RCC1) in diverse biological processes, including UV-B (ultraviolet-B radiation) response, hormonal signal transduction, cold tolerance and phenotypic plasticity, have been identified. No comprehensive study on the evolution and function of RCC1 gene family in rice has been carried out. A genome-wide analysis of this gene family is thus required. In this study, a total of 26 OsRCC1s unevenly distributed across 10 chromosomes were identified in rice. Based on their phylogenetic relationship and sequence composition, the OsRCC1 family could be classified into six groups. Members within the same group share a similar gene structure and protein motif/domain composition. Gene duplication analysis revealed that segmental duplication might be the main contributor to the expansion of the RCC1 gene family in rice. Several cis-regulatory elements (CREs) relevant to light, abscisic acid (ABA) and methyl jasmonate (MeJA) are abundant in the promoters of OsRCC1s. A large number of microRNA (miRNA) target sites were present in OsRCC1 mRNAs. Additionally, we used data from gene microarray and qRT-PCR to analyze the expression of OsRCC1 genes during various developmental stages and under abiotic stress conditions. OsRCC1s were found to be highly expressed in panicles and seeds, and most OsRCC1s were differentially expressed under abiotic stresses. Taken together, our study provides a systematic characterization of OsRCC1s and preliminarily explores their diversity as well as their biological functions. Evidence demonstrates that OsRCC1s may play vital roles in both development and abiotic stress response. The results presented here lay a foundation for further investigating the functions of OsRCC1s.

Exploring the Physiological Multiplicity of Native Microalgae from the Ecuadorian Highland, Italian Lowland and Indoor Locations in Response to UV-B

The differential effects of UV-B on the inhibition or activation of protective mechanisms to maintain cells photosynthetically active were investigated in native microalgae. Four strains were used, including two Chlorella sorokiniana strains, F4 and LG1, isolated from a Mediterranean inland swamp and a recycled cigarette butt's substrate, respectively, and two isolates from an Ecuadorian highland lake related to Pectinodesmus pectinatus (PEC) and Ettlia pseudoalveolaris (ETI). Monocultures were exposed to acute UV-B (1.7 W m-2) over 18 h under controlled conditions. UV-B-untreated microalgae were used as the control. Comparative physiological responses, including photosynthetic pigments, non-enzymatic antioxidants, and chlorophyll a fluorescence, were evaluated at specific time points. Results showed that UV-B significantly compromised all the physiological parameters in F4, thereby resulting in the most UV-B-sensitive strain. Contrarily, UV-B exposure did not lead to changes in the PEC physiological traits, resulting in the best UV-B-resistant strain. This could be attributed to the acclimation to high light habitat, where maintaining a constitutive phenotype (at the photosynthetic level) is strategically advantageous. Differently, LG1 and ETI at 12 h of UV-B exposure showed different UV-B responses, which is probably related to acclimation, where in LG1, the pigments were recovered, and the antioxidants were still functioning, while in ETI, the accumulation of pigments and antioxidants was increased to avoid further photodamage. Consequently, the prolonged exposure in LG1 and ETI resulted in species-specific metabolic regulation (e.g., non-enzymatic antioxidants) in order to constrain full photoinhibition under acute UV-B.

Proteomic analysis of Morus leaf epidermis indicates the roles of photosystems and ROS in UV-B response

The epidermis is the first layer of cells on leaves that receive UV-B radiation and the place where guard cells distribute. Their stress response mechanism was different from the mesophyll. However, there has been little research on leaf epidermis. To assess the response mechanism of epidermis to UV-B radiation, tissue-specific proteomics were performed on the epidermis of Morus leaf under UV-B radiation and UV-B radiation following dark incubation. A total of 935 proteins were identified and quantified. Changes of proteins involved in light reaction and Calvin cycle were not simultaneous. Antioxidant enzymes showed different patterns. And the contents of H2O2 and Ca2+ were increased after treatments. A UV-B radiation response mechanism of epidermis was proposed based on these results, in which photosystems perceives the stimulus of UV-B radiation to produce reactive oxygen species, and then the antioxidant system and protein homeostasis system were induced through the Ca2+ crosstalk with reactive oxygen species signaling pathway.

Integrated network analyses identify MYB4R1 neofunctionalization in the UV-B adaptation of Tartary buckwheat

A hallmark of adaptive evolution is innovation in gene function, which is associated with the development of distinct roles for genes during plant evolution; however, assessing functional innovation over long periods of time is not trivial. Tartary buckwheat (Fagopyrum tataricum) originated in the Himalayan region and has been exposed to intense UV-B radiation for a long time, making it an ideal species for studying novel UV-B response mechanisms in plants. Here, we developed a workflow to obtain a co-functional network of UV-B responses using data from more than 10,000 samples in more than 80 projects with multi-species and multi-omics data. Dissecting the entire network revealed that flavonoid biosynthesis was most significantly related to the UV-B response. Importantly, we found that the regulatory factor MYB4R1, which resides at the core of the network, has undergone neofunctionalization. In vitro and in vivo experiments demonstrated that MYB4R1 regulates flavonoid and anthocyanin accumulation in response to UV-B in buckwheat by binding to L-box motifs in the FtCHS, FtFLS, and FtUFGT promoters. We used deep learning to develop a visual discrimination model of buckwheat flavonoid content based on natural populations exposed to global UV-B radiation. Our study highlights the critical role of gene neofunctionalization in UV-B adaptation.

A newly developed and validated LC–MS/MS method for measuring 7-dehydrocholesterol (7DHC) concentration in human skin: a tool for vitamin D photobiology research

BackgroundUVB absorption by 7-dehydrocholesterol (7DHC) in the skin triggers the production of vitamin D and its metabolites, which maintain calcium homeostasis. Detection and measurement of 7DHC in skin using modern liquid chromatography–tandem mass spectrometry (LC–MS/MS) techniques have been lacking, yet there is need for such a technique to provide more information on 7DHC concentration and its UVB responses in human skin.ObjectivesTo develop and validate a reliable method to measure 7DHC concentration in skin.MethodsHuman skin punch biopsies of 5 mm diameter obtained through the Manchester Skin Health Biobank were utilised. 7DHC was extracted with ethyl acetate:methanol 1:1 (v/v) and derivatised using 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD), to allow for improved ionisation of 7DHC through Electrospray Ionisation Mass Spectrometry (ESI–MS). Solid supported liquid extraction (SLE) was also employed to allow the removal of larger lipids from 7DHC and minimise potential matrix effects.ResultsThe LC–MS/MS assay satisfied International Council for Harmonisation research standards for method validation. Calibration curve was linear with a typical r2 of 0.997, coefficient of variation was 11.1% and 4.32% for inter-assay and intra-assay imprecision, respectively. Lower limit of quantification was 1.6 µg/g and upper limit of quantification was 100 µg/g, SLE recovery of 7DHC was on average 91.4%.ConclusionsWe have developed a robust, precise and accurate assay for the detection and quantification of 7DHC in small samples of human skin (0.2 cm2 surface area). This novel method of extraction and quantification will be valuable to future vitamin D photobiology research.Graphical

Transcriptome and metabolome analyses revealed that narrowband 280 and 310\xa0nm UV-B induce distinctive responses in Arabidopsis

In plants, the UV-B photoreceptor UV RESISTANCE LOCUS8 (UVR8) perceives UV-B and induces UV-B responses. UVR8 absorbs a range of UV-B (260–335 nm). However, the responsiveness of plants to each UV-B wavelength has not been intensively studied so far. Here, we performed transcriptome and metabolome analyses of Arabidopsis using UV light emitting diodes (LEDs) with peak wavelengths of 280 and 310 nm to investigate the differences in the wavelength-specific UV-B responses. Irradiation with both UV-LEDs induced gene expression of the transcription factor ELONGATED HYPOCOTYL 5 (HY5), which has a central role in the UVR8 signaling pathway. However, the overall transcriptomic and metabolic responses to 280 and 310 nm UV-LED irradiation were different. Most of the known UV-B-responsive genes, such as defense-related genes, responded only to 280 nm UV-LED irradiation. Lipids, polyamines and organic acids were the metabolites most affected by 280 nm UV-LED irradiation, whereas the effect of 310 nm UV-LED irradiation on the metabolome was considerably less. Enzymatic genes involved in the phenylpropanoid pathway upstream in anthocyanin biosynthesis were up-regulated only by 280 nm UV-LED irradiation. These results revealed that the responsivenesses of Arabidopsis to 280 and 310 nm UV-B were significantly different, suggesting that UV-B signaling is mediated by more complex pathways than the current model.

Activation and negative feedback regulation of SlHY5 transcription by the SlBBX20/21-SlHY5 transcription factor module in UV-B signaling.

In tomato (Solanum lycopersicum) and other plants, the photoreceptor UV-RESISTANCE LOCUS 8 regulates plant UV-B photomorphogenesis by modulating the transcription of many genes, the majority of which depends on the transcription factor ELONGATED HYPOCOTYL 5 (HY5). HY5 transcription is induced and then rapidly attenuated by UV-B. However, neither the transcription factors that activate HY5 transcription nor the mechanism for its attenuation during UV-B signaling is known. Here, we report that the tomato B-BOX (BBX) transcription factors SlBBX20 and SlBBX21 interact with SlHY5 and bind to the SlHY5 promoter to activate its transcription. UV-B-induced SlHY5 expression and SlHY5-controlled UV-B responses are normal in slbbx20 and slbbx21 single mutants, but strongly compromised in the slbbx20 slbbx21 double mutant. Surprisingly, UV-B responses are also compromised in lines overexpressing SlBBX20 or SlBBX21. Both SlHY5 and SlBBX20 bind to G-box1 in the SlHY5 promoter. SlHY5 outcompetes SlBBX20 for binding to the SlHY5 promoter in vitro, and inhibits the association of SlBBX20 with the SlHY5 promoter in vivo. Overexpressing 35S:SlHY5-FLAG in the WT background inhibits UV-B-induced endogenous SlHY5 expression. Together, our results reveal the critical role of the SlBBX20/21-SlHY5 module in activating the expression of SlHY5, the gene product of which inhibits its own gene transcription under UV-B, forming an autoregulatory negative feedback loop that balances SlHY5 transcription in plants.

UV-B Irradiation Results in Inhibition of Hypocotyl Elongation, Cell Cycle Arrest, and Decreased Endoreduplication Mediated by miR5642.

UV-B as a component of natural solar radiation can induce damage and morphological development in plants. The UV-B response from germination and early development in seedlings is still largely unknown, with most studies focused on older, light-exposed seedlings. We used fluence response curves measuring hypocotyl length after UV-B exposure coupled with RNA-seq and sRNA-seq evaluation of the early seedling response in the model organism Arabidopsis thaliana. We identified miR5642 as a potential novel key regulator of UV-B responses. miR5642 is a noncanonical miRNA predicted to target previously known and unknown components involved in hypocotyl growth inhibition. These include (i) SMAX1, a signal transmitter for seedling germination and growth; (ii) ZAT1, an uncharacterized transcription factor; and (iii) membrane pores and transporters (VHA-E1, VHA-E3, EPSIN-LIKE and PIP1.4) implicated in cell elongation. In addition, HY5 and HYH, two homologous and redundant transcription factors involved in seedling photomorphogenesis, may interact with these newly identified components. Interestingly, UV-B-induced DNA photodimer formation seems to be the direct trigger leading to inhibition of hypocotyl growth through a combination of cellular decisions including cell cycle arrest, reduced endoreduplication and reduced cell elongation, and this inhibition appears to be modulated by miR5642 target genes.

Randomized controlled trial of fractionated laser resurfacing on aged skin as prophylaxis against actinic neoplasia.

BACKGROUNDThe loss of insulin-like growth factor 1 (IGF-1) expression in senescent dermal fibroblasts during aging is associated with an increased risk of nonmelanoma skin cancer (NMSC). We tested how IGF-1 signaling can influence photocarcinogenesis during chronic UVB exposure to determine if fractionated laser resurfacing (FLR) of aged skin, which upregulates dermal IGF-1 levels, can prevent the occurrence of actinic keratosis (AK) and NMSC.METHODSA human skin/immunodeficient mouse xenografting model was used to test the effects of a small molecule inhibitor of the IGF-1 receptor on chronic UVB radiation. Subsequently, the durability of FLR treatment was tested on a cohort of human participants aged 65 years and older. Finally, 48 individuals aged 60 years and older with considerable actinic damage were enrolled in a prospective randomized clinical trial in which they underwent a single unilateral FLR treatment of one lower arm. Numbers of AKs/NMSCs were recorded on both extremities for up to 36 months in blinded fashion.RESULTSXenografting studies revealed that chronic UVB treatment with a topical IGF-1R inhibitor resulted in a procarcinogenic response. A single FLR treatment was durable in restoring appropriate UVB response in geriatric skin for at least 2 years. FLR resulted in sustained reduction in numbers of AKs and decreased numbers of NMSCs in the treated arm (2 NMSCs) versus the untreated arm (24 NMSCs).CONCLUSIONThe elimination of senescent fibroblasts via FLR reduced the procarcinogenic UVB response of aged skin. Thus, wounding therapies are a potentially effective prophylaxis for managing high-risk populations.TRIAL REGISTRATIONClinicalTrials.gov (NCT03906253).FUNDINGNational Institutes of Health, Veterans Administration.

The Independent and Shared Transcriptomic Response to UVA, UVB and Oxidative Stress in the Cyanobacterium Nostoc punctiforme ATCC 29133.

Research on the UVA, UVB and oxidative (as reactive oxygen species, ROS) stress response in cyanobacteria has typically focused on each individual stress condition, with limited studies addressing the intersection. Here, we evaluated the transcriptomic responses of the model cyanobacterium Nostoc punctiforme after exposure to each of these conditions. Overall, response to UVA was characterized by more gene down-regulation than the UVB or ROS response, although UVB affected over fourfold more genes than UVA or ROS. Regarding expression patterns, responses to UVA and ROS were more similar and differentiated from those to UVB. For example, genes involved in ROS metabolism were up-regulated under both UVA and ROS. However, when it came to RNA and protein metabolism, there were more up-regulated genes under UVB and ROS compared to UVA. This suggests that the response to UVB and ROS is more active than the response to UVA, which stimulated more genes in secondary metabolism. Histidine kinases and response regulators were often differentially expressed, demonstrating that regulatory systems were at the base of the patterns. This study provides background for future studies targeting different genes, proteins and systems sensitive to these conditions. It also highlights the significance of considering multiple stress conditions.

Expression of Tomato UVR8 in Arabidopsis reveals conserved photoreceptor function

UV RESISTANCE LOCUS 8 (UVR8) is a photoreceptor that regulates UV-B photomorphogenesis in plants. UV-B photon perception promotes UVR8 homodimer dissociation into monomer, which is reverted to homodimer post UV-B, forming a complete photocycle. UVR8 monomer interacts with CONSTITUTIVELY PHOTOMORPHOGENEIC 1 (COP1) to initiate UV-B signaling. The function and mechanism of Arabidopsis UVR8 (AtUVR8) are extensively investigated, however, little is known about UVR8 and its signaling mechanisms in other plant species. Tomato is a widely used model plant for horticulture research. In this report we tested whether an ortholog of AtUVR8 in Tomato (SIUVR8) can complement Arabidopsis uvr8 mutant and whether the above-mentioned key signaling mechanisms of UVR8 are conserved. Heterologous expressed SIUVR8 in an Arabidopsis uvr8 null mutant rescued the uvr8 mutant in the tested UV-B responses including hypocotyl elongation, UV-B target gene expression and anthocyanin accumulation, demonstrating that the SIUVR8 is a putative UV-B photoreceptor. Moreover, in response to UV-B, SIUVR8 forms a protein complex with Arabidopsis COP1 in plants, suggesting conserved signaling mechanism. SIUVR8 exhibits similar photocycle as AtUVR8 in plants, which highlights conserved photoreceptor activation and inactivation mechanisms.