Salvia, glandular trichome

A quick dip of the aerial parts in ether has been used to extract the glandular trichome contents of Salvia glutinosa (194). The main component was the triterpenol, a-amyrin. Small amounts of flavones and flavonols were also Isolated. 

The prenyltransferases that catalyse the s)mtheses of GPP, FPP and GGPP may be important regulatory enz)mies in plant terpenoid bios)mthesis since they are situated at the primary branch points of the pathway, directing flux among the various major classes of terpenoids. The level of prenyltransferase activity is, in fact, closely correlated with the rate of terpenoid formation in many experimental systems (Dudley et at, 1986 Hanley et at, 1992 Hugueney et at, 1996) consistent with the regulatory importance of these catalysts. The localization of specific prenyltransferases in particular types of tissue or subcellular compartments may control the flux and direction of terpenoid synthesis at these sites. For example, the GPP synthase in Salvia officinalis is restricted to the secretory cells of the glandular trichomes, which are the sole site of monoterpene bios)mthesis in this species (Croteau and Purkett, 1989). 

Tirillini, B., A. Ricci, and R. Pellegrino. 1999. Secretion constitnents of leaf glandular trichomes of Salvia officinalis L. F ssent OilR., 11 565-569. 

Fig. 94.2 Glandular trichomes of sage Salvia officinalis) store essential oil composed of mono-terpenes. (a) Peltate glandular trichomes forming oil glands on lower leaf surface of sage, (b) Peltate glandular trichomes, capitate glandular trichomes and non-glandular trichomes on leaf veins of sage...

The most well-known producers of essential oil monoterpenes are herbs such as the mint (Mentha) and sage (Salvia) families. Arabidopsis thaliana does not form glandular trichomes and has only recently been found to produce monoterpenes (Chen etal. 2003). Genes coding for monoterpene synthases in Arabidopsis have been cloned and overexpressed (Bohlmann et al. 2000 Bouvier et al. 2000 Chen et al. 2003), but the biological role of the monoterpene products is presently imclear. 

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