Arabidopsis Flavonoid Mutants Are Hypersensitive to UV-B Irradiation

Li, Jiayang; Ou-Lee, Tsai-Mei; Raba, Richard; Amundson, Ronald; Last, Robert L.

doi:10.2307/3869583

Cited by 417 publications

(213 citation statements)

References 30 publications

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“…In particular, not a single phenylpropanoid compound has been identified in this species that would have a decisive role in disease resistance, despite the invariably observed strong induction of phenylpropanoid biosynthetic mRNAs and enzymes upon infection or elicitor treatment of A. thaliana (20,21). This apparent discrepancy is in contrast to the UV-light response in A. thaliana, which has been shown to be closely related to the accumulation of flavonoid glycosides and sinapoyl esters as well as the transcriptional activation of the responsible genes (22)(23)(24).…”

contrasting

confidence: 50%

“…This question seemed particularly relevant in view of both the previously established flavonoid and ferulate͞sinapate pathway interactions in A. thaliana (22) and more recent results, again obtained with parsley, indicating that induction of flavonoid biosynthesis has major effects on various supply pathways from primary metabolism (54) and thus may indirectly affect other biosynthetic capacities as well. Clearly, for the three classes of compounds investigated, flavonoid glycosides, sinapoyl esters, and indole derivatives, evidence for mutual interference with product accumulation rates was not obtained.…”

Section: Discussionmentioning

confidence: 99%

“…Of the three nonindolic compounds A, B, and G, the last, sinapoyl malate, has a proven role in UV resistance (22) but not in pathogen defense. Its decline upon infection is in line with both this functional assignment and the previous observation in parsley that the response to UV irradiation is strongly overridden by treatment with a pathogen-derived elicitor (53).…”

Section: Discussionmentioning

confidence: 99%

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Accumulation of soluble and wall-bound indolic metabolites in Arabidopsis thaliana leaves infected with virulent or avirulent Pseudomonas syringae pathovar tomato strains

Hagemeier¹

2001

Proceedings of the National Academy of Sciences

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The chemical structures and accumulation kinetics of several major soluble as well as wall-bound, alkali-hydrolyzable compounds induced upon infection of Arabidopsis thaliana leaves with Pseudomonas syringae pathovar tomato were established. All identified accumulating products were structurally related to tryptophan. Most prominent among the soluble substances were tryptophan, ␤-D-glucopyranosyl indole-3-carboxylic acid, 6-hydroxyindole-3-carboxylic acid 6-O-␤-D-glucopyranoside, and the indolic phytoalexin camalexin. The single major accumulating wall component detectable under these conditions was indole-3-carboxylic acid. All of these compounds increased more rapidly, and camalexin as well as indole-3-carboxylic acid reached much higher levels, in the incompatible than in the compatible P. syringae͞A. thaliana interaction. The only three prominent phenylpropanoid derivatives present in the soluble extract behaved differently. Two kaempferol glycosides remained largely unaffected, and sinapoyl malate decreased strongly upon bacterial infection with a time course inversely correlated with that of the accumulating tryptophan-related products. The accumulation patterns of both soluble and wallbound compounds, as well as the disease resistance phenotypes, were essentially the same for infected wild-type and tt4 (no kaempferol glycosides) or fah1 (no sinapoyl malate) mutant plants. Largely different product combinations accumulated in wounded or senescing A. thaliana leaves. It seems unlikely that any one of the infection-induced compounds identified so far has a decisive role in the resistance response to P. syringae.

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confidence: 50%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Accumulation of soluble and wall-bound indolic metabolites in Arabidopsis thaliana leaves infected with virulent or avirulent Pseudomonas syringae pathovar tomato strains

Hagemeier¹

2001

Proceedings of the National Academy of Sciences

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“…As a consequence, the cop1-4 mutant is impaired in the accumulation of flavonoids and the establishment of tolerance to UV-B. By contrast, under white light, cop1 mutants display elevated basal levels of CHS transcript and flavonoids compared with the wild type ( Figures 4B and 4C), which are potential sunscreen metabolites that may interfere with the UV-B response (Li et al, 1993). The phenotype of elevated flavonoid levels in cop1-4 is shared with det1-1, cop1 eid6 , and the spa quadruple mutant ( Figure 4B; Laubinger et al, 2004).…”

Section: Cop1 Regulation Of Uv-b-dependent Transcription and Photomormentioning

confidence: 99%

CONSTITUTIVELY PHOTOMORPHOGENIC1 Is Required for the UV-B Response in Arabidopsis

et al. 2006

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CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) is a negative regulator of photomorphogenesis in Arabidopsis thaliana. COP1 functions as an E3 ubiquitin ligase, targeting select proteins for proteasomal degradation in plants as well as in mammals. Among its substrates is the basic domain/leucine zipper (bZIP) transcription factor ELONGATED HYPOCOTYL5 (HY5), one of the key regulators of photomorphogenesis under all light qualities, including UV-B responses required for tolerance to this environmental threat. Here, we report that, in contrast with the situation in visible light, COP1 is a critical positive regulator of responses to low levels of UV-B. We show that in the cop1-4 mutant, flavonoid accumulation and genome-wide expression changes in response to UV-B are blocked to a large extent. COP1 is required for HY5 gene activation, and both COP1 and HY5 proteins accumulate in the nucleus under supplementary UV-B. SUPPRESSOR OF PHYTOCHROME A-105 family proteins (SPA1 to SPA4) that are required for COP1 function in dark and visible light are not essential in the response to UV-B. We conclude that COP1 performs a specific and novel role in the plants' photomorphogenic response to UV-B, coordinating HY5-dependent and -independent pathways, which eventually results in UV-B tolerance.

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“…Low fluence rates of UV-B promote the expression of a range of genes involved in UV-B protection (5,6,10,11). These include genes concerned with the production of flavonoids and other phenolic compounds that accumulate in the epidermal layers and provide a UV-absorbing sun screen (12,13). Other UV-B-induced genes are involved, for instance in ameliorating oxidative stress and repairing UV damage.…”

mentioning

confidence: 99%

A UV-B-specific signaling component orchestrates plant UV protection

Brown

Cloix

Jiang

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

497

792

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UV-B radiation in sunlight has diverse effects on humans, animals, plants, and microorganisms. UV-B can cause damage to molecules and cells, and consequently organisms need to protect against and repair UV damage to survive in sunlight. In plants, low nondamaging levels of UV-B stimulate transcription of genes involved in UV-protective responses. However, remarkably little is known about the underlying mechanisms of UV-B perception and signal transduction. Here we report that Arabidopsis UV RESISTANCE LOCUS 8 (UVR8) is a UV-B-specific signaling component that orchestrates expression of a range of genes with vital UV-protective functions. Moreover, we show that UVR8 regulates expression of the transcription factor HY5 specifically when the plant is exposed to UV-B. We demonstrate that HY5 is a key effector of the UVR8 pathway, and that it is required for survival under UV-B radiation. UVR8 has sequence similarity to the eukaryotic guanine nucleotide exchange factor RCC1, but we found that it has little exchange activity. However, UVR8, like RCC1, is located principally in the nucleus and associates with chromatin via histones. Chromatin immunoprecipitation showed that UVR8 associates with chromatin in the HY5 promoter region, providing a mechanistic basis for its involvement in regulating transcription. We conclude that UVR8 defines a UV-B-specific signaling pathway in plants that orchestrates the protective gene expression responses to UV-B required for plant survival in sunlight.photomorphogenesis ͉ ultraviolet-B radiation ͉ UV RESISTANCE LOCUS 8 U V-B radiation (280-320 nm) is an integral component of sunlight. UV-B can cause damage to macromolecules, including DNA, and generate reactive oxygen species. Because UV-B affects the growth, development, reproduction, and survival of many organisms, there is concern that any further increases in ambient levels of UV-B, resulting from stratospheric ozone depletion may have a significant impact on natural and agricultural ecosystems (1-4). Hence, it is important to understand how plants and other organisms protect themselves against the potentially damaging effects of UV-B.Exposure to UV-B is obligatory for higher plants because of the need to maximize light capture for photosynthesis. The effects of UV-B on diverse species of plants have been reported in the literature, and it is evident that different responses are observed at different UV-B fluence rates (5, 6). Exposure to high amounts of UV-B causes tissue necrosis and induces the expression of stressassociated genes in part through activation of pathogen-defense and wound-signaling pathways (5-7). At ambient UV-B levels, crosstalk between wound and UV-B signaling pathways modifies plantinsect interactions (8). Importantly, exposure to low nondamaging levels of UV-B has numerous regulatory effects on plant morphology, development, physiology, and biochemical composition (1,5,6,9). Low fluence rates of UV-B promote the expression of a range of genes involved in UV-B protection (5, 6, 10, 11). These include genes c...

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Arabidopsis Flavonoid Mutants Are Hypersensitive to UV-B Irradiation

Cited by 417 publications

References 30 publications

Accumulation of soluble and wall-bound indolic metabolites in Arabidopsis thaliana leaves infected with virulent or avirulent Pseudomonas syringae pathovar tomato strains

Accumulation of soluble and wall-bound indolic metabolites in Arabidopsis thaliana leaves infected with virulent or avirulent Pseudomonas syringae pathovar tomato strains

CONSTITUTIVELY PHOTOMORPHOGENIC1 Is Required for the UV-B Response in Arabidopsis

A UV-B-specific signaling component orchestrates plant UV protection

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