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Brockington Group: Why do plants accumulate animal-type neurotransmitters?

NERC / UF / OTHER

Supervisor: Sam Brockington (Plant Sciences)

Brief summary:

It is not widely appreciated that some plant species synthesis and accumulate substantial amounts of animal-type neurotransmitters such as dopamine and epinephrine, and the function of these metabolites for plants is substantially unknown.

Importance of the area of research concerned:

As sessile organisms, plants have evolved an array of specialized metabolites to adapt to their environments. Plants are consequently a rich source of metabolic diversity for biotechnology and have a significant role to play in the emerging bioeconomy. But specialized metabolites in plants are hugely diverse and the majority remain uncharacterized, with their functions in adaptation unknown. An example of these are the catecholamines such as L-DOPA, dopamine and norepinephrine. These metabolites are more widely known as important neurotransmitters in animals. But it is not widely appreciated that these are widely produced in many plants, including important crops, and also hyperaccumulate in some species such as banana. The adaptive significance of catecholamines in the context of plant biology is unknown, but preliminary evidence suggests roles in pathogen defense and storage tissue mobilization. Remarkably catecholamines also play an analogous role in storage tissue mobilization in animals. But the roles and function of these animal-type neurotransmitters in plants is a black-box, very little is known, and they are likely to be hugely significant for plant adaptation.

Project summary :

Our collaborators have characterised many species that hyperaccumulate catecholamines - L-DOPA, dopamine, epinephrine and hallucinogens such as mescaline. Using this phenomenon of hyperaccumulation we have characterised the pathway to dopamine synthesis, allowing us to knockout and upregulate this metabolite. In the context of this PhD, the identification of the enzyme for dopamine synthesis will enable the further elucidation of the pathways to epinephrine and mescaline which are downstream of dopamine. Having identified how to overexpress and knockdown these metabolites it will be possible to assess their roles in different adaptive scenarios and in plants development and physiology. Additionally, a number of insects are specialised feeders on plants that hyperaccumulate catecholamines, but the mechanisms insects have evolved to tolerate or sequester these toxic metabolites is unknown.

What will the student do?:

You will conduct RNA seq and co-expression to identify the two remaining enzymes in the synthesis of epinephrine. You will overexpress and knockdown these metabolites in their native context in the species Beta vulgaris. You will overexpress the same metabolites in the model organism Nicotiana benthamiana and assay their impact on feeding assays with various known plant pathogens such as nematodes, aphids, and fungi. You will examine the effect of overexpression on the development and physiology of model organisms such as Arabidopsis thaliana. You will assay the larvae of specialised feeders on catecholamine accumulating plants, and establish whether they can detect, avoid, or sequester these toxic metabolites.

References:

  • Soares AR, Marchiosi R, Siqueira-Soares Rde C, Barbosa de Lima R, Dantas dos Santos W, Ferrarese-Filho O. The role of L-DOPA in plants. Plant Signal Behav. 2014;9(3):e28275. doi:10.4161/psb.28275
  • Kuklin, A.I., Conger, B.V. Catecholamines in plants. J Plant Growth Regul 14, 91 (1995). https://doi.org/10.1007/BF00203119
  • Ramakrishna Akula & Soumya Mukherjee (2020) New insights on neurotransmitters signaling mechanisms in plants, Plant Signaling & Behavior, 15:6, DOI: 10.1080/15592324.2020.1737450

For details on how to apply to the Cambridge NERC Doctoral Training Partnerships see https://nercdtp.esc.cam.ac.uk/

 

 

 

 

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