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Publications - Cell and Metabolic Biology
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Sesquiterpene lactones (STLs) are bitter tasting plant specialized metabolites derived from farnesyl pyrophosphate (FPP) that contain a characteristic lactone ring. STLs can be found in many plant families that are distantly related to each other and outside the plant kingdom. They are especially prevalent in the plant families Apiaceae and Asteraceae, the latter being one of the largest plant families besides the Orchidaceae. The STL diversity is especially large in the Asteraceae, which made them an ideal object for chemosystematic studies in these species. Many STLs show a high bioactivity, for example as protective compounds against herbivory. STLs are also relevant for pharmaceutical applications, such as the treatment of malaria with artemisinin. Recent findings have dramatically changed our knowledge about the biosynthesis of STLs, as well as their developmental, spatial, and environmental regulation. This review intents to update the currently achieved progress in these aspects. With the advancement of genome editing tools such as CRISPR/Cas and the rapid acceleration of the speed of genome sequencing, even deeper insights into the biosynthesis, regulation, and enzyme evolution of STL can be expected in the future. Apart from their role as protective compounds, there may be a more subtle role of STL in regulatory processes of plants that will be discussed as well.
Publications
The pigments of Opuntia ficus‐indica fruits, which are derived from the betalain rather than anthocyanin pathway, have an extraordinary range in colour from lime green, orange, red to purple. This is a result from varying concentrations and proportions of about half a dozen betaxanthins and betacyanins. The yellow‐orange betaxanthins are derived from spontaneous condensation of betalamic acid with amines or amino acids. The reddish‐purple betacyanins are enzymatically formed from betalamic acid and cyclo ‐dihydroxyphenylalanine (DOPA) yielding betanidin and further glycosylated on either of the two hydroxyls of the cyclo ‐DOPA moiety. In the present work, degenerated primers were used to obtain partial genomic sequences of two major genes in the biosynthetic pathway for betalains, that is the 4,5‐extradiol dioxygenase which forms the betalamic acid responsible for the yellow colour and a putative 5‐O ‐glucosyltransferase which glycosylates betanidin in Dorotheanthus bellidiformis and may be responsible for the red colour. Differences in the genomic DNA between coloured versus non‐coloured varieties were not found. Regulatory mechanisms seem to independently control pigmentation of O. ficus‐indica fruit tissues for inner core, peel and epidermis. Core pigmentation occurs first and well before fruit maturity and peel pigmentation. Peel pigmentation is fully developed at maturity, presumably related to maximum soluble solids. Epidermal pigmentation appears to be independent of core and peel pigmentation, perhaps because of light stimulation. Similar control mechanisms exist through transcription factors for the major enzyme regulating anthocyanin production in grapes.
This page was last modified on 27 Jan 2025 .
