Integration of UV-B and temperature signalling in plants

Lead Research Organisation: University of Bristol
Department Name: Biological Sciences


Light and temperature are two of the most important signals regulating plant development. Thermomorphogenesis (developmental adaptation to non-stressful changes in ambient temperature) is a rapidly expanding field in plant biology with direct applications to crop productivity, ecology and biodiversity management in a changing climate. Although interactions between red/blue photoreceptors and high temperature signalling pathways have been identified, the integration of UV-B and high temperature signalling remains poorly characterised. In sunlight-grown plants, leaf temperature increases concomitantly with UV-B absorption. In contrast to the situation in the field, the majority of plant science is carried out in glasshouses and growth cabinets, conditions in which plants are exposed to little or no UV-B. Understanding how UV-B and high temperature signals are integrated is therefore central to our understanding of plant development in natural environments.

Our recently published work has identified a novel molecular mechanism through which UV-B, perceived by the UVR8 photoreceptor, inhibits high temperature-induced stem elongation. This provides plants with an important braking mechanism in bright sunlight, preventing excessive stem growth which could lead to lodging and critical reductions in biomass. The proposed programme will build on these findings to gain deeper molecular understanding of UV-B and temperature signal crosstalk. In particular, we wish to understand how UV-B regulates the transcript abundance and protein activity of the transcription factor, PIF4. Our results will have direct relevance to existing industrial collaborations aiming to reduce stem elongation in commercial horticulture, through UV-B supplementation.

Technical Summary

Elucidating how plants integrate UV-B and temperature signals is fundamental to understanding plant growth and development in sunlight. Towards this aim, we have recently shown that low dose UV-B, perceived by UVR8, inhibits high temperature-mediated stem elongation through suppressing the transcript abundance and activity of the bHLH transcription factor, PIF4. This reduces auxin biosynthesis, limiting cell elongation. This project aims to deepen molecular understanding of this process by firstly establishing whether UV-B regulates PIF4 promoter activity, transcript stability and/or histone acetylation. We will then dissect the molecular mechanisms through which UV-B regulates PIF4 protein activity at different temperatures. These include protein degradation, altered stability of the PIF4 inhibitor, HFR1 and a novel mechanism involving the bZIP transcription factor HYH.

Planned Impact

Plant UV-B and temperature responses have significant social, economic and ecological importance. In addition to controlling plant growth, both signals regulate plant metabolism, defence and abiotic stress tolerance. These wide-ranging effects make UV-B and temperature signalling prime targets for crop improvement. Furthermore, global warming makes understanding the effects of UV-B and elevated temperature on organisms and ecosystems a subject of key importance to policy makers.


The horticulture/forestry/viticulture industries: The stature and flowering time of glasshouse crops are commonly controlled through light quality manipulations. To date, these have focussed on red to far-red ratio and blue light which have much less potent effects on architecture than UV-B. The establishment of tree saplings and young vines requires tubular plastic shelters which significantly alter the spectra of light reaching plants and create a warm microclimate. Understanding how plants perceive and respond to low doses of UV-B at different temperatures will greatly facilitate the optimal design of plant growth regimes and growth materials (eg. tree shelters). Towards this aim, Franklin has existing BBSRC-supported industrial collaborations with Vitacress and GrowBristol to investigate the effects of UV-B supplementation on glasshouse-grown pot herbs and hydroponically-grown microgreens, respectively (see pathways to impact and letters of support).

Plant breeders: Increased understanding of UV-B signalling at different temperatures will facilitate the design of crops with optimal architecture, increased pest resistance and enhanced tolerance to climate change.

Policy makers: The ability of plants to survive and compete at elevated levels of UV-B and increased temperature will have significant impact on global food security, ecosystems and biodiversity. This project will therefore benefit policy makers, ecologists and conservationists.

Lab staff, postgraduate and undergraduate students: The provision of BBSRC funding will enable the training of both a PDRA and research technician in plant photobiology and a range of molecular biology techniques. This project will also provide training for MSci, undergraduate and summer students.


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Franklin KA (2020) PRR proteins of the circadian clock call time on shade avoidance. in Proceedings of the National Academy of Sciences of the United States of America

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Fraser DP (2021) Phytochrome A elevates plant circadian-clock components to suppress shade avoidance in deep-canopy shade. in Proceedings of the National Academy of Sciences of the United States of America

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Hayes S (2019) Soil Salinity Limits Plant Shade Avoidance. in Current biology : CB

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Sharma A (2023) ELONGATED HYPOCOTYL5 (HY5) and HY5 HOMOLOGUE (HYH) maintain shade avoidance suppression in UV-B. in The Plant journal : for cell and molecular biology

Description We have established that UV-B regulates the abundance of PHYTOCHROME INTERACTING FACTOR (PIF) proteins by sequestering CONSTITUTIVE PHOTOMORPHOGENESIS1 (COP1) protein. Our data explain why PIF protein levels are rapidly degraded in the presence of UV-B. This work has been published in Nature Communications. We have also established that UV-B perceived by UVR8 can regulate the gibberellin signalling pathway. UVR8-mediated up-regulation of the transcription factors HY5 and HYH increases the abundance of 2 GA2OXIDASE enzymes which increase DELLA stability, reducing PIF function. UVR8 additionally regulates XTH enzymes involved in cell wall loosening. This work was submitted to The Plant Journal. We were given an invited resubmission, pending additional experiments to show that UV-B increases the stability of HY5 protein. These have been completed and the manuscript is now being prepared for resubmission.
Exploitation Route We are currently working with agricultural engineers LettUs Grow to design light treatments to enhance the quality and shelf life of aeroponically-grown crops.
Sectors Agriculture, Food and Drink

Description BBSRC SWBio studentship on enhancing the stress tolerance and shelf life of horticultural crops through light quality manipulation
Amount £90,000 (GBP)
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 09/2020 
End 09/2024
Description Boostcrop- Boosting crop growth using natural product and synthesis enabled solar harvesting
Amount £4,900,000 (GBP)
Funding ID FET Open 
Organisation European Commission H2020 
Sector Public
Country Belgium
Start 01/2019 
End 01/2023
Description Evolution of plant thermomorphogenesis
Amount £103,106 (GBP)
Funding ID NIF\R1\201402 
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 04/2021 
End 04/2023
Description Royal Society Leverhulme Trust Senior Research Fellowship
Amount £54,034 (GBP)
Funding ID SRF \ R1 \ 201085 
Organisation The Leverhulme Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 09/2020 
End 09/2021
Description SWBio studentship on the role of UV-B in plant freezing tolerance
Amount £100,000 (GBP)
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 09/2018 
End 09/2022
Description Research collaboration with agricultural engineering company, LettUs Grow 
Organisation LettUs Grow
Country United Kingdom 
Sector Private 
PI Contribution We are helping to design light treatment protocools to enhance the quality and shelf life of aeroponically-grown crops.
Collaborator Contribution Access to their vertical farm in Bristol, seeds and plant growth materials.
Impact Too early.
Start Year 2020
Description Co-organised plant temperature responses session at the SEB annual meeting in Florence 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Potential new collaborations.
Year(s) Of Engagement Activity 2018
Description High School student summer work placement 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact My lab hosted a high school student from Dorset for a summer work experience placement. She has now decided to study a for a degree in Biology.
Year(s) Of Engagement Activity 2019
Description Presentation at the UK Controlled Environment User's Group (CUEC) annual conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact The UK Controlled Environment Users group includes managers of controlled environment facilities, users of controlled environments from university departments and research institutes, companies involved in plant research and representatives of manufacturers of controlled environment cabinets, rooms and glasshouses. I presented an overview of my research, highlighting the specific plant growth facilities we use. This resulted in some follow up enquiries from controlled environment facility managers at other universities.
Year(s) Of Engagement Activity 2018