Combinatorial biochemistry of triterpene saponins in plants

Plants are capable of synthesizing an overwhelming variety of secondary metabolites, many of which possess biological activities relevant for the pharmaceutical and chemical industries. Furthermore, there is an ever increasing demand for novel compounds, due to, among others, the growing drug tolerance and resistance in microorganisms and newly emerging diseases. In microorganisms, combinatorial biochemistry is a widely used tool to increase structural variation in several classes of (microbial) natural products. Despite the potential importance of plant secondary metabolites, only a limited fraction of these molecules is currently used, mostly due to their complex structure and the low production levels in planta. Metabolic engineering of plants has offered limited help because the molecular mechanisms steering plant secondary metabolism remain poorly characterized. Here, we used a functional genomics approach to identify candidate genes involved in the saponin biosynthesis of five different plants. After targeted metabolite profiling confirmed the induction of triterpene saponin biosynthesis by methyl jasmonate treatment, a genome-wide cDNA-AFLP transcript profiling was carried out for the five plants. Taking into account the putative functional annotation and the expression pattern of the visualized transcript tags, a set of 259 candidate genes potentially involved in saponin biosynthesis and its regulation were identified. The generated gene list provided the basis for a combinatorial biochemistry platform that targets triterpene saponins in plants. Proof of concept of combinatorial biochemistry was achieved by heterologous expression of the candidate saponin biosynthesis genes in M. truncatula hairy roots. Three of the generated transgenic hairy root lines were found to accumulate novel molecules, two of which were shown to be novel triterpene saponins, whereas the third line produced a set of novel, non-saponin compounds. Furthermore, the identified transcription factors and other regulators were lead candidates for studies investigating the control of the saponin biosynthesis in planta. This led to the identification of a RING membrane-anchor E3 ubiquitin ligase, MAKIBISHI1 (MKB1), that targets 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), the enzyme catalyzing the rate-limiting step in the mevalonate pathway, for ubiquitin-mediated proteasomal degradation, thereby controlling saponin biosynthesis.

Grantor dc:publisher

Ghent University. Faculty of Sciences

Year dc:date

2011

Author dc:creator

• Pollier, Jacob

Contributors dc:contributor

• Goossens, Alain

• Biology and Life Sciences
• Transcript Profiling
• Triterpene Saponins
• Combinatorial Biochemistry
• Natural Products
• Secondary Metabolites
• Metabolite Profiling

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://biblio.ugent.be/publication/1853820
https://biblio.ugent.be/publication/1853820/file/4335657

OAI identifier oai:identifier

oai:archive.ugent.be:1853820