Integrating UV-B signalling in to plant photomorphogenesis networks

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.

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.

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.