Light-independent sugar signalling in Arabidopsis

Lead Research Organisation: University of York
Department Name: Biology

Abstract

Sugar metabolism is a fundamental biological process providing energy and the molecular building blocks to sustain life on our planet. 'Green organisms', such as plants and algae, use light energy from the sun to convert carbon dioxide into stored energy in the form of sugars while producing the oxygen we breathe. This process, known as photosynthesis, is probably the most important metabolic process on the planet. Photosynthetic organisms living in the 'primordial soup' produced the oxygen which gave rise to the Great Oxidation Event ~2.5 billion years ago, facilitating a massive evolutionary advance. Plants are among the descendants of these organisms, which continue to provide most of the energy necessary to sustain life today. Therefore, investigating how plants sense and respond to sugars is a fundamentally important research question in biology. Through improved understanding of these processes, we can gain valuable insight and develop tools to improve efficiency and total productivity of agriculture to feed the growing population around the world.
Since photosynthesis depends on light, it must be effectively regulated to optimise use of daylight. Sugars must be transported to tissues that cannot photosynthesise to meet their energy needs and stored appropriately to last the night. Furthermore, as daylength and seasons change, plants need to be able to adapt to the changes in environment while maintaining optimal carbohydrate metabolism. Coordination of these processes requires mechanisms for plants to sense and respond to sugar availability. The requirement for light in sugar production in plants adds complexity that is a critical consideration to understand these endogenous sugar signalling pathways in photosynthetic organisms. For example, it is difficult to interpret effects of sugars in the light when photosynthesis is active. There is still much to be learned about the underlying mechanisms in these processes. The main objective of this research is to identify novel components of sugar signalling in the model plant species, Arabidopsis thaliana. A novel, sensitive assay has been developed to investigate sugar responses that act independently of light signalling in plants. This assay will be used to identify genes that contribute to light-independent responses to sugars and determine the function of these genes in the context of various, physiologically relevant growth environments. Ultimately, the goal of this research is gain insight into how plants integrate sugar and light signals to optimise photosynthetic efficiency and growth. This work will use a range of genetic and molecular approaches, utilising state-of-the-art technologies to gain genome-wide information about the impacts of these processes.

Technical Summary

Carbohydrate metabolism is a fundamental biological process providing energy and the molecular building blocks for life. In plants, sugars are produced from photosynthesis in a light-dependent manner. Photosynthesis is probably the most important metabolic process on the planet. Understanding how plants sense and respond to sugars is therefore a fundamental research question in biology because, in addition to the role in energy storage, sugars regulate growth, developmental, flowering time, pathogen resistance, cell cycle progression and circadian entrainment. The requirement for light in sugar production in plants adds complexity that is a critical consideration to understand endogenous sugar signalling pathways in photosynthetic organisms.
Sugar signalling pathways in plants have been identified so far either by genetic screens for resistance to very high exogenous sucrose in the light or inferred from animal or yeast systems. While these approaches have been successful in identifying components of plant sugar sensing and signalling, there remains much to be learned about these processes. A more sensitive genetic screen for a physiologically relevant sugar-dependent response would provide a powerful tool to uncover plant-specific sugar signalling components.
A genetic screen, based on a novel sugar response assay, has identified mutants that affect sugar signalling independently of light and photosynthesis. Mutants will be mapped and characterised in the context of various physiologically relevant growth environments. A high quality transcriptome dataset will be generated to define global transcriptional events in wild type and mutant plants in response to sugars in the context of light signalling and photosynthesis. This research will identify molecular components of sugar signalling and advance our understanding of how external light signals and endogenous sugar signals are integrated to optimise plant growth and development.

Planned Impact

Who might benefit from this research?
1. The PDRA
2. Industrial and commercial scientists interested in plant energy biology and/or sustainable agriculture
3. The general public
How might they benefit from this research?
1. The research programme provides an exciting opportunity for an early career scientist to acquire a wide range of professional skills that are applicable to either an academic or non-academic career.
Within a research context, the PDRA will gain experience and training in broadly applicable, state-of-the-art technologies for gene and protein expression analysis for biological research. This research will be conducted to world-class standards and is expected to have high academic impact. Therefore, this project has the potential to progress the academic career of the researcher. The publication record of Dr Haydon demonstrates a strong track record of academic impact with a high quality of research output. The PDRA will also have the opportunity to interact with world-class biological scientists at the University of York, collaborating partners of the research lab, and while attending an international conference. These networking opportunities will facilitate the next step in his/her career, if an academic path is desired.
The PDRA will also gain experience and training in a range of broadly relevant, non-academic skills including management of research students and technical staff, oral and written presentation, use of general and specialised software and computing tools and effective time-management and organisation. Training will be provided both informally within the context of the research group and formally from training courses provided by the department and the university.
2. Although the research project is focused on fundamental research into biological processes in plants, there is potential for this research to benefit agriculture and the plant science industry. The research builds on recently published, high impact research and will advance our knowledge of energy sensing and carbon metabolism, which are fundamental to all biological systems. Carbohydrate metabolism in plants not only supplies biomass for plant growth but also provides almost all the fixed carbon and oxygen for life on this planet and so has broad implications not only for agriculture but also the environment. This field of research is highly relevant to urgent problems associated with climate change and resource demands because plant carbohydrate metabolism lies at the foundation of energy storage for bio-fuels and provides a major pathway for carbon sequestration. Therefore, contributions to our understanding of sugar metabolism in plants is relevant to achieving the recognised goals of improving sustainable agricultural yields to support the rapidly growing population around the world, enhancing the potential of biofuels and minimising impact of climate change. The impact could be indirect, through the open-access publication of research outcomes, or could be direct by specific interaction with potential industrial and commercial partners as outlined in the pathways to impact.
3. Breakthrough findings towards understanding fundamental biological questions have high potential to make an impact on the general population through the popular science media. This can be facilitated by publication of research outputs in widely recognised scientific journals, publicity through press releases and through public outreach. Public outreach can be achieved at a number of levels such as interaction through the internet and social media, participation in university open days targeted at students and families and, ultimately, through involvement in science media such as podcasts and radio programmes. Effective use of these means of public engagement will ensure this research contributes to increasing public awareness and understanding of the importance of fundamental questions in the biological sciences.

Publications

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Haydon MJ (2015) Nutrient homeostasis within the plant circadian network. in Frontiers in plant science

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Haydon MJ (2016) Assessing the Impact of Photosynthetic Sugars on the Arabidopsis Circadian Clock. in Methods in molecular biology (Clifton, N.J.)

 
Description We have developed transgenic lines to detect cell-type specific transcriptional responses in Arabidopsis seedlings, and have used them to detect tissue-specific behaviour of sugar-regulated and circadian reporters. Analyses of the comprehensive transcriptomic experiment to dissect light and sugar networks is complete and has produced a rich dataset, including providing evidence for unexplored signalling pathways required for metabolic signalling. Specifically, this pointed to a role of reactive oxygen species signalling, which we have confirmed using pharmacological and genetic tools (manuscript in preparation). Thus, despite the technical and experimental difficulties associated with mapping sourpuss mutants, we have achieved all objectives.
Exploitation Route This research project has generated a rich data resource for our labs, which will be made available to the community in due course. In combination with a chemical genetic approach in the Haydon lab, the project has opened exciting new pathways to investigate and manipulate metabolic signalling pathways in Arabidopsis. This will have significant impact for the research community. Furthermore, the chemical genetic approach, in particular, is highly tractable to other species, including crops or weeds, and so has strong potential to impact agriculture in the long term. This is an ongoing research activity in the Haydon lab.
Sectors Agriculture, Food and Drink

URL https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5619894/
 
Description The principal finding from the research project is that reactive oxygen species contribute to sugar-regulated gene expression in Arabidopsis. This represents a novel component of plant sugar signalling that controls plant growth. This finding will contribute to a manuscript which will be submitted in 2020 and provided substantial preliminary data for a grant submission to the Australian Research Council in 2020. The experimental challenges faced with the genetic approaches in this project prompted us to switch to a chemical biology approach, supported by a small Royal Society Grant. This has opened possibilities to target these metabolic signalling pathways with improved precision and potential for agrochemical development. In this project, we also developed a new reporter system to measure spatiotemporal gene expression in Arabidopsis. This was published in Plant Journal in 2019. This tool is broadly applicable to report tissue-specific gene promoter activity. We will continue to use this tool to investigate sugar signalling and make this available to the Arabidopsis research community.
First Year Of Impact 2015
Sector Agriculture, Food and Drink
Impact Types Economic

 
Description BBSRC DTP REPS
Amount £2,500 (GBP)
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 07/2015 
End 09/2015
 
Description Internal Research Grants Support Scheme - Award to co-investigator, Dr Mike Haydon, providing 3 months funding to ARF for April to June 2018.
Amount $530,000 (AUD)
Organisation University of Melbourne 
Sector Academic/University
Country Australia
Start  
 
Description Royal Society Research Grant
Amount £15,000 (GBP)
Funding ID RG150144 
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2015 
End 09/2016
 
Title A tool to measure spatiotemporal promoter activity in Arabidopsis 
Description In multicellular organisms different types of tissues have distinct gene expression profiles associated with specific function or structure of the cell. Quantification of gene expression in whole organs or whole organisms can give misleading information about levels or dynamics of expression in specific cell types. Tissue- or cell-specific analysis of gene expression has potential to enhance our understanding of gene regulation and interactions of cell signalling networks. The Arabidopsis circadian oscillator is a gene network which orchestrates rhythmic expression across the day/night cycle. There is heterogeneity between cell and tissue types of the composition and behaviour of the oscillator. In order to better understand the spatial and temporal patterns of gene expression, flexible tools are required. By combining a Gateway®-compatible split luciferase construct with a GAL4 GFP enhancer trap system, we developed a tissue-specific split luciferase assay for non-invasive detection of spatiotemporal gene expression in Arabidopsis. This enhancer trap-compatible split luciferase assay (ETSLA) system can be used to investigate tissue-specific dynamics of circadian gene expression. Resources are available to investigate any gene of interest. 
Type Of Material Technology assay or reagent 
Year Produced 2019 
Provided To Others? Yes  
Impact Research outputs as described in Román et al., 2019. 
URL https://onlinelibrary.wiley.com/doi/full/10.1111/tpj.14603
 
Description Dr Mike Haydon (project co-investigator) was a speaker at ComBio 2018 held in Sydney, Australia 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Dr Mike Haydon gave a talk entitled 'Reactive oxygen species contribute to sugar signalling and growth in Arabidopsis' and presented some of the work from this project.
Year(s) Of Engagement Activity 2018
 
Description FAPESP-British Council Workshop on Plant Metabolism and Development 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Networking opportunity between young UK and Brazilian scientists. Stimulated discussions about potential collaborations and opportunities for funding.

Several UK scientists from the meeting have subsequently been invited to York to strengthen links and share information.
Year(s) Of Engagement Activity 2015
 
Description Poster presentation, ComBio 2016 conference, Brisbane, Australia 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Dr Mike Haydon (former project PI) presented a poster at the ComBio conference. This is the main biology conference in Australia, attended by about 800 delegates (both Australian and international).
Year(s) Of Engagement Activity 2016
 
Description Talk given by Dr Angela Roman-Fernandez at July 2018 SEB Gothenberg meeting 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Project PDRA, Angela Roman-Fernandez, gave a research talk on the project titled 'Light-independent sugar signalling in Arabidopsis'.
Year(s) Of Engagement Activity 2017
URL http://www.sebiology.org/docs/default-source/Events-library/seb-gothenburg-2017---full-programme.pdf...
 
Description Talk given by Dr M Haydon (co-investigator) at Plant Biology 2017 conference in Honolulu, USA 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Dr Mike Haydon presented a talk titled "Sugar-dependent interactions of ZEITLUPE and ethylene with GIGANTEA in the circadian clock", at the Plant Biology 2017 conference in Honolulu, USA, in June 2017. The talk included data that had been published in the 2017 Plant Physiology paper.
Year(s) Of Engagement Activity 2017
URL https://www.eventscribe.com/2017/ASPB/agenda.asp?h=Fulld16fe96044744ca4384ac69a3cbffd3ead9432ad7621c...
 
Description Talk given by co-investigator (Dr Mike Haydon) at ComBio 2017 conference in Adelaide, Australia 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Research presentation given by Dr Mike Haydon titled "Sweet timing: roles for sugar signals in circadian time-keeping". The talk included data from the recently published Plant Physiology paper.
Year(s) Of Engagement Activity 2017
URL http://combio.org.au/combio2017//docs/2017%20COMBIO%20-%20Final%20Full%20Program%2024.08.17.pdf