Til bevillingsoversigt

Improving the production and storage capacity of valuable metabolites in plants

Carlsbergfondets internationaliseringsstipendier

What

The objective of this study is to develop methods to increase the capacity of plants to produce and store terpenoids of nutritional and pharmaceutical value. The initial focus of the research will be on lycopene and β-carotene belonging to the class of terpenoid metabolites called carotenoids. The project will investigate the cytosol as a place for carotenoid biosynthesis, as opposed to the plastids, where carotenoid biosynthesis is highly regulated. High cytosolic carotenoid levels can however cause necrosis in the leaves. This supports the necessity of increasing the storage capacity of plant cells to accumulate lipophilic metabolites and avoid toxicity. The potential of producing and storing carotenoids in modified endoplasmic reticulum structures is the main objective.

Why

Carotenoids are valued in crop species due to their nutritional and health-promoting value. Lycopene is especially recognised as the red pigment that gives the colour to ripe tomatoes and watermelons. It is also a powerful anticancer agent and an intermediate in the biosynthesis of other carotenoids. This includes β-carotene, the main precursor for the production of vitamin A in the diet. By producing carotenoids outside their normal compartment the aim is to circumvent the regulatory network currently affecting carotenoid levels in plants. Investigating the endoplasmic reticulum as a storage place has important implications for production of not only carotenoids but also valuable diterpenoids.

How

As a proof of concept, the model plant Nicotiana tabacum (tobacco) will be used as a host to upregulate the production of precursor molecules for carotenoids and diterpenoids using cytosolic and ER-anchored enzymes. The abundance of ER-derived endomembrane structures will be increased by using an ER-anchoring domain demonstrated in the host lab to stimulate ER membrane proliferation. In these plants, ER-derived vesicles are expected to contain the engineered enzymes but also provide a proper storage compartment for terpenoids. Tobacco lines producing high levels of precursors will next be used to produce lycopene and β-carotene in leaves after transient expression of the appropriate enzymes. The tobacco lines will be screened for increased storage and accumulation of metabolites.

SSR

This research study is an important part of developing plants that can function as high yielding production platforms for valuable compounds. It contributes to the establishment of future biofortified crops, with eg. higher nutritional value. Working around the current limitations for high production, as for instance the highly developed regulatory networks, offers interesting and far reaching opportunities. Using new methods for storage of carotenoids and diterpenoids will also allow the growth of healthy plant with high levels of health promoting or pharmaceutical compounds of interest. These methods combined contributes to higher yields with less space and nutrition needed compared to what is possible today.