The role of the MEP and mevalonate pathways in the biosynthesis of isoprenoids in cotton
Zusammenfassung der Projektergebnisse
The discovery of a second isoprenoid biosynthetic pathway in plants was one of the major advances in plant biochemistry of the last 20 years. Starting from glyceraldehyde-3-phosphate and pymvate, this new pathway produces C-5 units for the formation of different terpene classes by a route completely distinct from that of the mevalonate pathway. The new pathway also seems to be present in different subcellular compartments than the mevalonate pathway. In this project, isotope ratio mass spectrometry (IRMS) of the natural abundance of 13C/12C isotopes (δ13C values) was found to be a suitable method to determine the flexible pathway utilization in the formation of terpenoids in leaves of cotton (Gossypium hirsutum L. (Malvaceae)) and flowers of Hesperis matronalis L. (B ras sic ace ae). The results indicated significant variability in the participation of each pathway of terpenoid biosynthesis depending on abiotic factors such as light and biotic factors such as herbivoryby Spodoptera littoralis larvae. The combination of pathway specific inhibitor treatments and IRMS measurements was especially useful in monitoring pathway utilization. Feeding experiments with labeled precursors on intact cotton plants revealed the exchange of intermediates between the pathways, which varies among organs. The data demonstrate that the formation of isoprenoid stmctures in cotton plants is tightly regulated by compartmentation and enzyme activities and that the organ-specific utilization of the MVA or MEP pathway is responsible for the differences in the isoprenoid pattems and isotopomer distribution. The project represents an important step to understand the role of two isoprenoid pathways and their interplay. The results will lay the foundation for future studies on the formation and regulation of the plant isoprenoids, the largest group of low molecular weight compounds in plants, and facilitate efforts to manipulate the levels of individual metabolites.
Projektbezogene Publikationen (Auswahl)
- Opitz S, Kunert G, Gershenzon J: Increased terpenoid accumulation in cotton (Gossypium hirsutum) foliage is a general wound response. Joumal of Chemical Ecology 34, 508- 522
