Integrating UV-B signalling in to plant photomorphogenesis networks

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

Abstract

In addition to supplying energy for photosynthesis, light provides plants with important spatial and seasonal information. Light signals are perceived by specialised photoreceptors, which include the red and far-red light-absorbing phytochromes and the blue light-absorbing cryptochromes. Although a minor component of sunlight, UV-B radiation (280-315 nm) is a major regulator of plant metabolism and development. The much sought-after UV-B photoreceptor has recently been identified as the 7-bladed propeller protein, UVR8. Although plants perceive the full sunlight spectrum, UV-B signalling has traditionally been studied in isolation from other photoreceptor networks. The dwarf phenotype of UV-B-treated plants is well-established but the molecular mechanisms underpinning this striking developmental adaptation are unknown. Our recent work has identified a novel molecular mechanism through which UV-B regulates plant architecture, via direct crosstalk with phytochrome and cryptochrome signalling pathways. The proposed research programme will build on these exciting findings to gain deeper molecular understanding of sunlight signalling in plants. More specifically, we aim to understand how UV-B perceived by UVR8 controls the agriculturally-important shade avoidance response.

Technical Summary

The recent ground-breaking discovery that UVR8 functions as a UV-B photoreceptor provides a timely opportunity to understand sunlight signalling in plants. Towards this aim, we have already established direct crosstalk between UVR8 and phytochrome signalling pathways in the regulation of plant growth, via converged regulation of the key transcriptional regulators, PHYTOCHROME INTERACTING FACTORs (PIFs). This project aims to dissect the molecular mechanisms through which UV-B signals control PIF abundance and activity. Furthermore, we aim to understand how phytochrome, cryptochrome and UVR8 signalling pathways converge to regulate plant architecture in dense canopies through detailed molecular analysis of the shade avoidance syndrome.

Planned Impact

Plant UV-B responses have significant social, economic and ecological importance. In addition to modulating plant growth, UV-B regulates plant metabolism, defence and abiotic stress tolerance. These wide-ranging effects make UV-B signalling a prime target for crop improvement. Furthermore, human depletion of the stratospheric ozone layer makes understanding the effects of elevated UV-B on organisms and ecosystems a subject of key importance to policy makers.

Beneficiaries:

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

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. The establishment of tree saplings and young vines requires tubular plastic shelters which significantly alter the spectra of light reaching plants. Understanding how plants perceive and respond to low doses of UV-B will greatly facilitate the optimal design of plant growth regimes and consumables.Towards this aim, Franklin has existing industrial collaborations with Tubex to optimise treeshelter design and VHB to investigate the effects of UV-B supplementation on glasshouse-grown pot herbs (see pathways to impact).

Policy makers: The ability of plants to survive and compete at elevated levels of UV-B 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. In addition, it will provide training in plant physiology, a strategically important research skill, recently highlighted by the Royal Society as being in decline and in urgent need of investment (Royal Society Report (2009) Reaping the benefits: Science and the sustainable intensification of global agriculture. http://royalsociety.org). This project will also provide training for MSci, undergraduate and summer students.

Publications

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Franklin KA (2016) Photomorphogenesis: Plants Feel Blue in the Shade. in Current biology : CB

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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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Fraser DP (2016) Photoreceptor crosstalk in shade avoidance. in Current opinion in plant biology

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

 
Description 1. A key objective of this award is to understand how UV-B signals inhibit plant stem growth. The PHYTOCHROME INTERACTING FACTOR (PIF) transcription factors 4, 5 and 7 promote stem growth by promoting synthesis of the plant hormone auxin. We had previously shown that UV-B leads to rapid degradation of the PIF transcription factors. A major output from this study was a detailed understanding of how UV-B inhibits high temperature-mediated stem elongation. We have shown that UV-B inhibits PIF4 transcript accumulation and promotes PIF4 protein degradation in a temperature-independent manner. At high temperature, UV-B stabilises the transcription factor HFR1 which binds to PIF4 and inhibits PIF4 activity. We additionally identified a novel role for the transcription factor HYH. This work has been published (Hayes et al. 2017 Current Biology 27, 120-127). Further work involving PIF5 has been published (Sharma et al. 2019 Nature Communications 10: 4417). 2. A second objective involved investigating whether UV-B induced flavonoid accumulation contributes to the UV-B-mediated inhibition of stem elongation. We showed that this wasn't the case using mutants deficient in flavonoid biosynthesis. This has been published (Fraser et al. 2018, Scientific Reports 7). 3. A third output from this work has shown that our findings in Arabidopsis are translatable to glasshouse horticulture. Working with our industrial partner, Vitacress, we have shown that UV-B supplementation can produce more compact coriander plants which have a greater market value. This work has been published (Fraser et al. 2018, Scientific Reports, 7).
Exploitation Route 1. We are currently working with Vitacress (the UK's largest supplier of potted herbs) to investigate ways in which UV-B lighting can be used to improve plant quality in commercial horticulture. Excessive stem growth can reduce the shelf life and value of potted herbs. UV-B supplementation produces a more compact plant and therefore improves product quality. 2. PIF transcription factors are major integrators of plant environmental signalling. Understanding their regulation by UV-B will therefore be of interest to a wide variety of plant biologists.
Sectors Agriculture, Food and Drink,Environment

URL https://www.cell.com/current-biology/fulltext/S0960-9822(16)31329-X?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS096098221631329X%3Fshowall%3Dtrue
 
Description We have an industrial collaboration with Vitacress herbs to investigate the role of UV-B light on potted herb architecture. Our findings have established that although UV-B supplementation is effective at enhancing crop quality, it is not cost- or energy- efficient. These findings have formed the basis of a further BBSRC CASE studentship to investigate the effects of UV-B transmitting glass on potted herb quality.
First Year Of Impact 2017
Sector Agriculture, Food and Drink
Impact Types Economic

 
Description BBSRC IAA
Amount £20,000 (GBP)
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 04/2016 
End 02/2017
 
Description BBSRC responsive mode
Amount £410,707 (GBP)
Funding ID BB/R002045/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 04/2018 
End 04/2022
 
Description GrowBristol 
Organisation GrowBristol
Country United Kingdom 
Sector Private 
PI Contribution We provided intellectual input and resources to the project
Collaborator Contribution GrowBristol provided materials and technical expertise on the vertical farming of microgreens.
Impact 1. We found that UV-B supplementation could increase the antioxidant content of microgreens but had little effect on plant architecture and appearance. This was likely due to the very short growing period of these plants (7 days).
Start Year 2016
 
Description Vitacress 
Organisation Vitacress Salads ltd
Country United Kingdom 
Sector Private 
PI Contribution We provided the intellectual input and resources to the project.
Collaborator Contribution Vitacress provided materials, glasshouse space and knowledge of herb growth and glasshouse lighting protocols.
Impact 1. We have shown that UV-B supplementation can produce more compact, higher value, coriander plants with a higher leaf antioxidant content. This work has been published (Fraser et al. 2017, Scientific Reports 7).
Start Year 2014
 
Description GrowBristol 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Industry/Business
Results and Impact We had regular meetings with local urban farming company, GrowBristol, to discuss the use of photomorphogenesis research in vertical farming. A technician from the lab presented her work to the general public at a GrowBristol open day.
Year(s) Of Engagement Activity 2017
 
Description Open day research presentations 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Multiple research talks to prospective students and their parents at University open days and department visit days.
Year(s) Of Engagement Activity 2015,2016,2017,2018
 
Description RHS award publicity 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Publicity for the award of the Marsh Christian Trust award for Horticultural Science on the funder's website, the Royal Horticultural Society website and in the RHS magazine. This award was given to my PhD student for his work on UV-B control of plant architecture.
Year(s) Of Engagement Activity 2017
URL http://www.marshchristiantrust.org/award/marsh-horticultural-science-award/
 
Description Vitacress 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Multiple discussions with research managers at Vitacress herbs about the application of plant light signalling research in commercial horticulture.
Year(s) Of Engagement Activity 2014,2015,2016,2017,2018