Trends in Plant Science
ReviewUV-B photoreceptor-mediated signalling in plants
Section snippets
Plants and their light environment
Plants are sessile photoautotrophic organisms and thus must constantly adapt to surrounding environmental factors for optimal growth and development. Light in particular is an environmental factor of utmost importance to plants. It is not only the source of energy, driving photosynthesis, but also an informational signal directing plant development from germination to flowering. Plants sense the quality (wavelength), intensity, duration (including day length) and direction of light, and these
UV-B perception by the UVR8 photoreceptor
UVR8 is a β-propeller protein originally identified in a screen for Arabidopsis mutants hypersensitive to UV-B [13]. Under light conditions that specifically activate the UV-B photoreceptor pathway, UVR8 proteins are absolutely required for UV-B responses [14]. By contrast, at increased UV-B levels UV-B stress responses are maintained in the uvr8 mutant [15].
The UVR8 protein is localised in the cytoplasm and the nucleus and its abundance is unaffected by UV-B or other light qualities 14, 16.
UVR8-mediated signal transduction
UVR8 must be associated with a molecular signalling pathway for UV-B perception to be translated into plant photomorphogenesis and UV-B acclimation. However, only few of the molecular players involved in UVR8-mediated UV-B signal transduction are currently known. Regardless, there is solid evidence that COP1 and HY5, two common elements in light signalling, both play major roles in promoting UV-B-induced photomorphogenesis (Figure 3).
Negative feedback regulation of the UVR8 signalling pathway
The enhanced UV-B photomorphogenic response in transgenic UVR8 overexpression lines is associated with dwarf growth, highlighting the importance of achieving balance between UV-B-specific responses and plant growth [14]. A negative feedback regulation of UVR8 signalling by the UVR8-interacting REPRESSOR OF UV-B PHOTOMORPHOGENESIS1 (RUP1) and RUP2 proteins has recently been described [43]. RUP1 and RUP2 were identified and described in parallel as EARLY FLOWERING BY OVEREXPRESSION 1 (EFO1) and
UVR8-mediated UV-B responses
The identification of UVR8 as the UV-B photoreceptor now allows investigation of UVR8 involvement in known UV-B responses, as already shown for gene expression, UV-B acclimation and tolerance, and hypocotyl growth inhibition 13, 14, 17. Involvement of UVR8 in the control of endoreduplication and leaf morphogenesis, including stomatal differentiation, has also been proposed [48]. HY5 was recently implicated in UV-B-mediated cotyledon expansion [49], suggesting that UVR8 also plays a role in this
Commonalities with and differences to visible light signalling
In common with some of the other plant photoreceptors (in response to their respective wavebands), UVR8 accumulates rapidly in the nucleus in response to UV-B, requires UV-B to be activated (e.g. nuclear localization is not sufficient for UV-B signalling), interacts directly with COP1, uses HY5 as a downstream effector and is regulated by a negative feedback pathway. The fact that COP1 and HY5 are major downstream effectors in UV-B as well as in visible light signalling indicates high potential
Concluding remarks and future outlook
Significant progress has been made over recent years in identifying the molecular players and understanding the early mechanisms and functions of the UV-B perception and signalling pathway in plants. The perception of UV-B by UVR8 followed by UVR8–COP1 interaction has emerged as a primary mechanism of the UV-B response that is crucial for UV-B acclimation and tolerance. However, several open questions remain regarding the photochemistry, signal transduction and regulatory mechanisms of UVR8
Acknowledgements
We would like to thank Marina Gonzàlez Besteiro, Kimberley Tilbrook and Pat King for helpful comments on the manuscript. Research in the Ulm laboratory is supported by the University of Geneva, the Emmy Noether Programme (Grant UL341/1-1) and the Swiss National Science Foundation (Grant no. 31003A_132902).
References (67)
UV-B as an environmental factor in plant life: stress and regulation
Trends Ecol. Evol.
(1997)- et al.
Ecological roles of solar UV radiation: towards an integrated approach
Trends Ecol. Evol.
(2003) Light-regulated plant growth and development
Curr. Top. Dev. Biol.
(2010)The action mechanisms of plant cryptochromes
Trends Plant Sci.
(2011)- et al.
Signalling and gene regulation in response to ultraviolet light
Curr. Opin. Plant Biol.
(2005) Plant stress and human health: Do human consumers benefit from UV-B acclimated crops?
Plant Sci.
(2008)- et al.
Interaction of the Arabidopsis UV-B-specific signaling component UVR8 with chromatin
Mol. Plant
(2008) - et al.
COP1 – from plant photomorphogenesis to mammalian tumorigenesis
Trends Cell Biol.
(2005) Blue light-dependent interaction of CRY2 with SPA1 regulates COP1 activity and floral initiation in Arabidopsis
Curr. Biol.
(2011)Purification of the yeast PHR1 photolyase from an Escherichia coli overproducing strain and characterization of the intrinsic chromophores of the enzyme
J. Biol. Chem.
(1987)
The role of the pyridoxine (vitamin B6) biosynthesis enzyme PDX1 in ultraviolet-B radiation responses in plants
Plant Physiol. Biochem.
root uv-b sensitive mutants are suppressed by specific mutations in ASPARTATE AMINOTRANSFERASE2 and by exogenous vitamin B6
Mol. Plant
The degradation of HFR1, a putative bHLH class transcription factor involved in light signaling, is regulated by phosphorylation and requires COP1
Curr. Biol.
Changes in biologically active ultraviolet radiation reaching the Earth's surface
Photochem. Photobiol. Sci.
Perception of UV-B by the Arabidopsis UVR8 protein
Science
Effects of solar ultraviolet radiation on terrestrial ecosystems. Patterns, mechanisms, and interactions with climate change
Photochem. Photobiol. Sci.
Repair of DNA damage induced by solar UV
Photosynth. Res.
Signal transduction in responses to UV-B radiation
Annu. Rev. Plant Biol.
Arabidopsis UVR8 regulates ultraviolet-B signal transduction and tolerance and contains sequence similarity to human regulator of chromatin condensation 1
Plant Physiol.
Interaction of COP1 and UVR8 regulates UV-B-induced photomorphogenesis and stress acclimation in Arabidopsis
EMBO J.
Arabidopsis MAP kinase phosphatase 1 and its target MAP kinases 3 and 6 antagonistically determine UV-B stress tolerance, independent of the UVR8 photoreceptor pathway
Plant J.
UV-B promotes rapid nuclear translocation of the Arabidopsis UV-B specific signaling component UVR8 and activates its function in the nucleus
Plant Cell
A UV-B-specific signaling component orchestrates plant UV protection
Proc. Natl. Acad. Sci. U.S.A.
CONSTITUTIVELY PHOTOMORPHOGENIC1 is required for the UV-B response in Arabidopsis
Plant Cell
FHY1 and FHL act together to mediate nuclear accumulation of the phytochrome A photoreceptor
Plant Cell Physiol.
Photoexcited CRY2 interacts with CIB1 to regulate transcription and floral initiation in Arabidopsis
Science
Blue-light-dependent interaction of cryptochrome 1 with SPA1 defines a dynamic signaling mechanism
Genes Dev.
Arabidopsis cryptochrome 1 interacts with SPA1 to suppress COP1 activity in response to blue light
Genes Dev.
A light-switchable gene promoter system
Nat. Biotechnol.
The third chromophore of DNA photolyase: Trp-277 of Escherichia coli DNA photolyase repairs thymine dimers by direct electron transfer
Proc. Natl. Acad. Sci. U.S.A.
Lightening up the UV response by identification of the arylhydrocarbon receptor as a cytoplasmatic target for ultraviolet B radiation
Proc. Natl. Acad. Sci. U.S.A.
Is the photoactive yellow protein a UV-B/blue light photoreceptor?
Photochem. Photobiol. Sci.
Cited by (353)
UV-B reduction and excess: Management strategies regarding Coffea sp. crop
2024, Scientia HorticulturaeThe potential of gamma irradiation on antioxidant capacity and genomic alterations in Calendula officinalis
2023, Applied Radiation and IsotopesInvestigating physiological responses of Wild Rocket subjected to artificial Ultraviolet B irradiation
2023, Scientia HorticulturaeEffective strategies to enhance ultraviolet barrier ability in biodegradable polymer-based films/coatings for fruit and vegetable packaging
2023, Trends in Food Science and Technology