Divining Roots: uncovering how SUMO-mediated responses control developmental plasticity

Food security represents a major global issue. Significant improvements in crop yields are urgently required to meet the increase in world population by 2050. The ability of a crop to efficiently absorb water and nutrients from soil is dependent on its root system responding to the availability of these resources. For example, roots preferentially form branches when in contact with water employing a mechanism called hydropatterning. Understanding the regulation of root branching is of vital agronomic importance.

This research project will investigate how hydropatterning works to position new root branches in response to water availability. Our research project attempts to 'fill in the gaps' between roots sensing water availability and then branching. To help our studies, we have already identified plant signals and genes such as auxin and ARF7 that are important for this process. Several promising processes will also be characterised including one that modifies ARF7 that switches on root branching. The knowledge gained from this study will provide new information about the key genes and processes controlling root branching in response to water availability, helping scientists design novel approaches to manipulate root architecture to enhance resource capture and yield in crops.

Root branching is influenced by the soil environment to improve foraging efficiency. For example, lateral roots initiate and develop towards the availability of water employing a novel adaptive response termed hydropatterning. We recently identified the molecular mechanism regulating hydropatterning (Orosa et al, 2018, Science). In brief, this mechanism involves the SUMO-dependent post-translational modification of the lateral root regulator ARF7. SUMOylation of ARF7 is required to recruit the Aux/IAA repressor protein IAA3. Blocking ARF7 SUMOylation disrupts IAA3 recruitment and hydropatterning. We conclude that this new form of auxin regulation controls root branching pattern in response to water availability.

The new BBSRC proposal takes this research beyond ARF7 and addresses how SUMO-mediated environmental responses control hydropatterning. In objective 1, we initially address whether a hydropatterning stimulus modifies ARF7 SUMO status by altering the stability and/or activity of SUMO machinery components. Objective 2 will determine which root tissue ARF7 SUMOylation takes place to trigger hydropatterning. In objective 3, we will pinpoint the ARF7 gene targets required to be asymmetrically expressed to promote hydropatterning. Finally, objective 4 will explore whether IAA3 controls hydropatterning via just ARF7 or interacts with other SUMOylated transcription factors. By unravelling the SUMO mediated signal transduction pathway during hydropatterning we lay the foundations for understanding a major regulator of plant-environmental responses.

The knowledge generated about the new signals, genes and their regulatory pathways will underpin on going efforts to re-engineer root systems architecture and improve crop performance. The expertise, resources and tools that have been assembled for this project at Nottingham and Durham with our international collaborators uniquely position us to successfully complete this project.

Who will benefit from this research?
Life science researchers
Agronomists and plant breeders
Industrial collaborators
Members of the public

How will they benefit from this research?
The project will generate a number of new and innovative experimental tools, data resources and models that a wide spectrum of researchers from other disciplines would be interested in employing. For example, Life Scientists could employ similar approaches to study SUMO-regulated processes in other biological systems; plant breeders and agronomists will use the information generated about SUMO and its target genes and processes in breeding studies and/or to design new approaches to manipulate root branching in crops, forestry and horticultural varieties. This award would also help establish a knowledge base that will allow by Industrial collaborators, to be explored, helping generate IP and new products with the information. Members of the public would gain access to images and movies of root systems via the web-based 'Hidden Half' interface as part of this project.

Data generated during the project will be stored in accordance with UKAS guidelines and published in peer-reviewed journals. All biological materials generated will be deposited at the Nottingham Arabidopsis Stock Centre (NASC); whilst light sheet movies will be deposited at https://mediaspace.nottingham.ac.uk/tag/tagid/the%20hidden%20half for public access.

The project will also help train researchers experienced with working as part of a multidisciplinary team. This multidisciplinary expertise will uniquely position them for employment in the UK Life Science and Pharmaceutical Industries.

In terms of timescales of benefits, selected data and materials generated would be made publically available during the period of the award as outlined above and in accordance with our data release statement (see Data Management Plant for details). Staff would be available to enter the UK work force in 2022. Application of findings made by the award to create, for example, new products and IP, is anticipated to be on the scale of 5-10 years.

Engagement with end users and beneficiaries about the project:
The PI, co-Is and PDRAs will disseminate their results at scientific conferences, through published journal articles, annual IP review with PBL and at our annual Nottingham Research Innovation and Impact Showcase with >100 commercial organisations.

Datasets providing light sheet microscopy images and movies of root systems will be added to the web-based 'Hidden Half' interface as part of this project.