| 1. |
- Neugart, Susanne, et al.
(author)
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Ultraviolet-B radiation exposure lowers the antioxidant capacity in the Arabidopsis thaliana pdx1.3-1 mutant and leads to glucosinolate biosynthesis alteration in both wild type and mutant
- 2020
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In: Photochemical and Photobiological Sciences. - : Royal Society of Chemistry. - 1474-905X .- 1474-9092. ; 19:2, s. 217-228
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Journal article (peer-reviewed)abstract
- Pyridoxine (vitamin B6) and its vitamers are used by living organisms both as enzymatic cofactors and as antioxidants. We used Arabidopsis pyridoxine biosynthesis mutant pdx1.3-1to study involvement of the PLP-synthase main polypeptide PDX1 in plant responses to ultraviolet radiation of two different qualities, one containing primarily UV-A (315-400 nm), the other containing both UV-A and UV-B (280-315 nm). The antioxidant capacity and the flavonoid and glucosinolate (GS) profiles were examined. As indicator of stress, Fv/Fmof photosystem II reaction centers was used. In pdx1.3-1, UV-A+B exposure led to a significant 5% decrease in Fv/Fmon the last day (day 15), indicating mild stress at this time point. Antioxidant capacity of Col-0 wildtype increased significantly (50-73%) after 1 and 3 days of UV-A+B. Instead, in pdx1.3-1, the antioxidant capacity significantly decreased by 44-52% over the same time period, proving the importance of a full complement of functional PDX1genes for detoxification of reactive oxygen species. There were no significant changes in flavonoid glycoside profile under any light condition. However, the GS profile was significantly altered, both with respect to Arabidopsis accession and exposure to UV. The difference in flavonoid and GS profiles reflect that the GS biosynthesis pathway contains at least one pyridoxine-dependent enzyme, whereas no such enzyme is used in flavonoid biosynthesis. Also, there was strong correlation between the antioxidant capacity and the content of some GS compounds. Our results show that vitamin B6vitamers, functioning both as antioxidants and co-factors, are of importance for physiological fitness of plants.
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| 2. |
- Qian, Minjie, et al.
(author)
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UV-A light induces a robust and dwarfed phenotype in cucumber plants (Cucumis sativus L.) without affecting fruit yield
- 2020
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In: Scientia Horticulturae. - : Elsevier. - 0304-4238 .- 1879-1018. ; 263
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Journal article (peer-reviewed)abstract
- Solar ultraviolet (UV) light influences plant growth and metabolism. Whereas high doses of UV can be deleterious for plants, natural UV doses are important for morphogenesis in many plants species, including those used in horticulture. Greenhouses are widely used for horticultural production and common cladding materials strongly absorb UV. Thus, low amounts of UV may be limiting the optimal development in some plant species. Light supplementation using UV tubes can overcome UV deficiency. Here we study cucumber seedling production in the absence or presence of different UV wavelengths. UV-A- (315-400 nm) and UV-B- (280-315 nm) enriched light was used for exposure and parameters such as the maximum quantum yield of photosystem II, stem development (internode length and diameter, stem dry weight, stem weight per unit of stem length, and stem bending), root biomass, leaf biomass and specific leaf mass were measured. We found that UV-A supplementation resulted in shorter more compact and sturdy plants, properties that are positive from a horticultural perspective. In contrast, UV-B-enriched light led to even smaller plants that lacked the sturdy phenotype. There were no signs of decreased Fv/Fmunder any of the treatments, nor statistically significant differences in fruit yield between the control plants and the UV-treated plants when grown to harvest. In particular, the differences in fruit yield between the controls and the UV-A-treated plants were negligible in all cases. Thus, supplementary UV-A light can be an interesting alternative to chemical growth regulators for production of sturdy horticultural plants.
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| 3. |
- Castro Alves, Victor, 1986-, et al.
(author)
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The taste of UV light : Using sensomics to improve horticultural quality
- 2020
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In: UV4Plants Bulletin. - Helsingfors : University of Helsinki. - 2343-323X. ; :1, s. 39-43
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Journal article (peer-reviewed)abstract
- Greenhouse horticulture is in its broad definition the production of plant products within, under or sheltered by structures that provide protection against biotic and/or abiotic stress. In greenhouses, horticultural crops can grow protected from infectious agents and adverse weather conditions, allowing off-season, year-round production. However, greenhouse production often comes with a trade-off, which is a skewed light environment with a lack of UV light. In some instances, the blockage of UV by greenhouse glass and plastic covers is beneficial from a commercial perspective, especially on tropical latitudes where plants can often encounter higher UV levels, which may impair plant growth and nutrient absorption (Krause et al. 1999; Verdaguer et al. 2017). On the other hand, reduced UV inside greenhouses may reduce the synthesis of metabolites associated with crop protection against biotic and abiotic stress, such as flavonoids, terpenoids and alkaloids (Yang et al. 2018). This reduction in the amount of protective compounds may not be seen as an important limitation in a protected environment, but these metabolic changes caused by reduced UV exposure may in fact negatively impact on product quality. For example, it is possible to improve of the aroma and taste of greenhouse tomato by exposing plants to low levels of supplementary UV light (Dzakovich et al. 2016).
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| 4. |
- Ni, Junbei, et al.
(author)
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Ethylene mediates the branching of the jasmonate-induced flavonoid biosynthesis pathway by suppressing anthocyanin biosynthesis in red Chinese pear fruits
- 2020
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In: Plant Biotechnology Journal. - : Wiley-Blackwell. - 1467-7644 .- 1467-7652. ; 18:5, s. 1223-1240
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Journal article (peer-reviewed)abstract
- Flavonoid accumulation in most fruitsis enhanced by ethylene and jasmonate. However, little is known about the hormone functions related to red pear fruit coloration or their combined effects and potential underlying mechanisms. Various treatments were used to investigate the flavonoid metabolite profile and pear transcriptome to verify the effects of ethylene and jasmonate on flavonoid biosynthesis in red pear fruits as well as the mechanism behind this. Ethylene inhibits anthocyanin biosynthesis in red Chinese pear fruits, whereas jasmonate increases anthocyanin and flavone/isoflavone biosyntheses. The branching of the jasmonate-induced flavonoid biosynthesis pathway is determined by ethylene. Co-expression network and Mfuzz analyses revealed 4,368 candidate transcripts. Additionally, ethylene suppresses PpMYB10 and PpMYB114 expression via TF repressors, ultimately decreasing anthocyanin biosynthesis. Jasmonate induces anthocyanin accumulation through transcriptional or post-translational regulation of TFs like MYB and bHLH in the absence of ethylene. However, jasmonate induces ethylene biosynthesis and the associated signaling pathway in pear, thereby decreasing anthocyanin production, increasing the availability of the precursors for flavone/isoflavone biosynthesis, and enhancing deep yellow fruit coloration. We herein present new phenotypes and fruit coloration regulatory patterns controlled by jasmonate and ethylene, and confirm that the regulation of fruit coloration is complex.
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| 5. |
- Rai, Neha, et al.
(author)
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The photoreceptor UVR8 mediates the perception of both UV-B and UV-A wavelengths up to 350 nm of sunlight with responsivity moderated by cryptochromes
- 2020
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In: Plant, Cell and Environment. - : John Wiley & Sons. - 0140-7791 .- 1365-3040. ; 43:6, s. 1513-1527
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Journal article (peer-reviewed)abstract
- The photoreceptors UV RESISTANCE LOCUS 8 (UVR8) and CRYPTOCHROMES 1 and 2 (CRYs) play major roles in the perception of UV-B (280–315 nm) and UV-A/blue radiation (315–500 nm), respectively. However, it is poorly understood how they function in sunlight. The roles of UVR8 and CRYs were assessed in a factorial experiment with Arabidopsis thaliana wild-type and photoreceptor mutants exposed to sunlight for 6 h or 12 h under five types of filters with cut-offs in UV and blue-light regions. Transcriptome-wide responses triggered by UV-B and UV-A wavelengths shorter than 350 nm (UV-Asw) required UVR8 whereas those induced by blue and UV-A wavelengths longer than 350 nm (UV-Alw) required CRYs. UVR8 modulated gene expression in response to blue light while lack of CRYs drastically enhanced gene expression in response to UV-B and UV-Asw. These results agree with our estimates of photons absorbed by these photoreceptors in sunlight and with in vitro monomerization of UVR8 by wavelengths up to 335 nm. Motif enrichment analysis predicted complex signaling downstream of UVR8 and CRYs. Our results highlight that it is important to use UV waveband definitions specific to plants’ photomorphogenesis as is routinely done in the visible region.
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| 6. |
- Santin, Marco, et al.
(author)
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The outer influences the inner : postharvest UV-B radiation modulates peach flesh metabolome although shielded by the skin
- 2020
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In: Food Chemistry. - : Elsevier. - 0308-8146 .- 1873-7072.
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Journal article (peer-reviewed)abstract
- UV-B-driven modulation of secondary metabolism in peach fruit by enhancing the biosynthesis of specific phenolic subclasses, is attracting interest among consumers. However, current literature explored the UV-B-induced metabolic changes only in peach skin subjected to direct UV-B irradiation. Accordingly, this study aimed to understand whether UV-B radiation penetrates the fruit skin and is able to induce metabolic changes also within the inner flesh. Peaches were UV-B irradiated either 10 or 60 min, and the flesh was sampled after 24 and 36 h. Non-targeted metabolomics revealed that UV-B has a strong impact on peach flesh metabolome, determining an initial decrease after 24 h, followed by an overall increase after 36 h, particularly for terpenoids, phenylpropanoids, phytoalexins and fatty acids in the 60 min UV-B-treated samples (+150.02, +99.14, +43.79 and +25.44 log2FC, respectively). Transmittance analysis indicated that UV-B radiation does not penetrate below the skin, suggesting a possible signalling pathway between tissues.
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