Solar UV light regulates flavonoid metabolism in apple (Malus x domestica)

Ultraviolet‐B light (UV‐B) is one environmental signal perceived by plants that affects the flavonoid pathway and influences the levels of anthocyanins, flavonols, and proanthocyanidins. To understand the mechanisms underlying UV exposure, apple trees were grown under spectral filters that altered t...

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Bibliographic Details
Published in:Plant, cell and environment cell and environment, 2018-03, Vol.41 (3), p.675-688
Main Authors: Henry‐Kirk, Rebecca A., Plunkett, Blue, Hall, Miriam, McGhie, Tony, Allan, Andrew C., Wargent, Jason J., Espley, Richard V.
Format: Article
Language:English
Subjects:
Agricultural production
anthocyanin
Anthocyanins
Biosynthesis
Crop production
Crops
Elongation
environmental effects
Exposure
Filters
Flavonoids
Flavonols
Fruit trees
Fruits
Functional analysis
Functional testing
Gene expression
Gene regulation
Genes
HY5
Light
Light levels
Malus domestica
Metabolism
MYB
Physiology
Proanthocyanidins
Ripening
Transcription
Trees
Ultraviolet radiation
UV light
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Summary:Ultraviolet‐B light (UV‐B) is one environmental signal perceived by plants that affects the flavonoid pathway and influences the levels of anthocyanins, flavonols, and proanthocyanidins. To understand the mechanisms underlying UV exposure, apple trees were grown under spectral filters that altered transmission of solar UV light. Fruit analysis showed that UV induced changes in physiology, metabolism, and gene expression levels during development over a season. These changes were sustained after storage. Under low UV, ripening was delayed, fruit size decreased, and anthocyanin and flavonols were reduced. Expression analysis showed changes in response to UV light levels for genes in the regulation and biosynthesis of anthocyanin and flavonols. Transcription of flavonol synthase (FLS), ELONGATED HYPOCOTYL 5 (HY5), MYB10, and MYB22 were down‐regulated throughout fruit development under reduced UV. Functional testing showed that the FLS promoter was activated by HY5, and this response was enhanced by the presence of MYB22. The MYB22 promoter can also be activated by the anthocyanin regulator, MYB10. As ambient levels of UV light vary around the globe, this study has implications for future crop production, the quality of which can be determined by the response to UV. In this manuscript, we examined the mechanisms underlying UV exposure of apple trees grown under spectral filters that altered transmission of solar UV light. The experiment was conducted in the orchard so that we could examine relevant effects. Fruit analysis showed that UV induced changes in physiology, metabolism, and gene expression levels during development. The most fundamental of these changes was a severe reduction in fruit size under restricted UV exposure. Many of these UV‐induced changes were sustained well after harvest. Expression and functional analysis showed changes in genes involved in the regulation and biosynthesis of anthocyanin and flavonols. This study has implications for future crop production, the quality of which can be determined by the response to UV. We feel that this work is directly relevant to the readers of PC&E.
ISSN:0140-7791
1365-3040
DOI:10.1111/pce.13125