The regulation of quantitative variation of foliar terpenes in medicinal tea tree Melaleuca alternifolia

Background Terpenes are important mediators of plant-environment interactions as well as often being economically important. Terpenes are biosynthesized via two spatially separate pathways: the MEP pathway in the plastid, the site of monoterpene biosynthesis and the MVA pathway in the cytosol, the site of sesquiterpene biosynthesis (McGarvey and Croteau 1995; Eisenreich et al. 1998; Rohmer 1999). Studies using transgenic plants have demonstrated that when the MEP genes dxs and dxr and MVA pathway gene hmgr are up-regulated plants exhibit an increase in foliar terpene concentrations (Chappell et al. 1995; Wildung and Croteau 2005; Carretero-Paulet et al. 2006). However, as yet, the importance of the expression of these genes has not been demonstrated for naturally occurring quantitative variation in foliar terpene concentrations.