L-DOPA and catecholamines in plants

Catecholamines are a class of small chemical molecules. They include important animal neurotransmitters and hormones such as dopamine, norepinephrine (noradrenaline) and epinephrine (adrenaline). The function and biosynthesis of catecholamines is well-known in animals, however they also occur in plants where their function and biosynthesis are much less understood. They likely act as defence molecules against other living things, such as by harming competing plants or predatory insects, and they may have a role in protection against environmental stresses, such as drought. They also may influence carbohydrate levels in the plant, a role reminiscent of the regulation of insulin by dopamine in animals. Overall, however, data on the function of catecholamines in plants is very limited. Catecholamines are also very interesting from an evolutionary biology perspective. They almost certainly arose independently in plants and animals and may also have arisen several times independently in different plant species. This prompts questions such as: Are there multiple ways to biosynthesise catecholamines? Are similar types of genes and enzymes involved in different species? Did catecholamines evolve to serve a similar function in different species? Currently, evolutionary and functional insights are limited by our lack of knowledge of how these compounds are made in plants. Therefore, this project aims to determine the biosynthetic pathway that produces catecholamines in plants. To achieve the overall aim of the project, the catecholamine biosynthetic pathway will be determined in three plant species, representing at least two evolutionary origins of these compounds: Beta vulgaris (beet), Mucuna pruriens (velvet bean) and Vicia faba (faba be an). The scientific approaches used to do this will include using cutting-edge nucleic acid sequencing technologies combined with the chemical analysis of catecholamine levels in different tissues of the plants. Enzymes thought to be involved in catalysing the biochemical reactions will be validated by using biochemical approaches and by producing transgenic plants in which enzyme function has been perturbed. Those enzymes that are proven to be involved in catecholamine biosynthesis will then be compared between species in order to determine their evolutionary history and relationships. This project will represent the first time that the catecholamine biosynthetic pathway has been determined in any plant species. Determining the pathway in multiple plant species will then provide the foundation from which to compare how catecholamines evolved in these species, as well as between plants and animals. The genetic resources developed during the project will also provide insights into the function of catechol amines in plants and will provide an indispensable basis for ongoing research in this area.