Identification and characterisation of microbial effectors that interfere with the plant circadian rhythm

Lead Research Organisation: University of Warwick
Department Name: School of Life Sciences

Abstract

Plant microbial pathogens secrete multiple effector proteins into plant cells in order to interfere with the plant immune system. Subsequently, plants have evolved multiple receptors capable to recognise these effectors, leading to an evolutionary arms race between pathogen and host. The plant circadian clock is essential for effective immune responses to pathogens by regulating the stomatal aperture and the levels of immune receptors. Therefore the clock is a likely target for microbial effectors. The aim of this project is to identify clock interfering effectors, elucidate the molecular mechanism of their virulent function and subsequently use them in synthetic biology approaches in an effort to engineer high performing plants.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
BB/M01116X/1 01/10/2015 30/09/2023
1643126 Studentship BB/M01116X/1 05/10/2015 30/09/2019 Olivia Nippe
 
Description In the same way that humans can become synchronised to their environment as a way of maintaining good health (the sleep wake cycle), so too can plants. These so called circadian rhythms are 24 hours oscillations in biological processes that enable organisms to function efficiently, preserving energay and resources for when they would be most useful. It was previously seen that plants time their immune responses such that they are more susceptible to bacterial infection at certain times of day (for instance at dawn when dew on leaves created a damp environment that facilitates bacterial infection of inner leaf tissues).

Because bacteria evolve at a much faster rate than multicellular organisms such as plants, there is a school of thought that if anything is involved in the immune system, they will probably already have evolved a mechanism to disrupt that mechanism to aid their own infection of a host. Thus, if the internal clock mechanism of a plant can influence immunity, bacteria can probably disrupt the clock in turn. My project sought to understand how bacteria might disrupt the plant interal clock in order to induce time-of-day dependent immune susceptibility.

We discovered a number of bacterial proteins known as effectors are able to induce disruptions in the plant clock when presented alone to plant cells. This supports our hypothesis that bacteria are able to dysregulate the plants inner genetic timekeeping ability.

One of these bacterial effector proteins interacts with a specific transcription factor, a protein that is able to change the amount a specific gene is expressed. The transcription factor in question is known to alter expression of genes that control the plant clock. Not only that, but the effector in fact enhanced the ability of the transcription factor to bind to that clock gene. We believe this is mechanistic evidence of a bacterial protein disrupting the plant clock as a way of hindering immune function.

We also found that this effector, which was previously only known to impact plant expression of immune system genes when in the cytoplasm, is also able to induce host genetic changes in the nucleus, and that coordinate function by the effector in both areas of the cell is required for the immune system to be maximally disrupted.

By improving our understanding of how A) this one particular effector can impact disease in plants and B) which bacterial proteins are able to disrupt the plant internal timekeeping mechanism we have provided new insight into plant disease, and present ample new avenues for research that warrant further study and would enable the design of more disease resistant crops.
Exploitation Route By clarifying the way by which this effector interacts with a clock associated transcription factor to induce host genetic changes, it could be that we could identify a way to prevent this mechanism from being enacted in plants. This would no doubt prevent the infection of plants by this bacteria- in this case P. syringae, a blight-causing, hemibiotrophic bacterium.

If we could prevent the disruption of the clock in plants by invading pathogens, this would benefit plant fitness and could prevent disease, and be used to genetically engineer more disease resistant crops.
Sectors Agriculture, Food and Drink

 
Description European Cooperation in Science and Technology (E-COST)
Amount € 2,500 (EUR)
Funding ID COST-STSM-ECOST-STSM-FA1208-040117-081632 
Organisation European Cooperation in Science and Technology (COST) 
Sector Public
Country Belgium
Start 01/2017 
End 03/2017
 
Description Second Grand Challenges in Plant Pathology Interdisciplinary Study Group 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact The second Grand Challenges in Plant Pathology Interdisciplinary Study Group took place at Chicheley Hall from 25-28th September 2018. The meeting was attended by 30 graduate and post-graduate researchers and 9 champions from 25 universities, research institutes, non-profit organisations and industry.
Year(s) Of Engagement Activity 2018