Localization of enzymes of artemisinin biosynthesis to the apical cells of glandular secretory trichomes of Artemisia annua L.

OSC2 and CYP716A14v2 Catalyze the Biosynthesis of Triterpenoids for the Cuticle of Aerial Organs of Artemisia annua

“…In addition, the glandular trichomes have been proposed to be the primary site for artemisinin biosynthesis and storage in the plant (Duke et al, 1994;Van Nieuwerburgh et al, 2006;Olsson et al, 2009;Wang et al, 2013). In our comparative transcriptome analysis, transcripts corresponding to putative or known monoterpenoid, diterpenoid, and (most) sesquiterpenoid biosynthesis genes were overrepresented in the glandular trichomes, as opposed to the triterpenoid transcripts, which were abundant in the filamentous trichomes (Soetaert et al, 2013).…”

“…The glandular trichomes in A. annua are composed of five pairs of cells: three pairs of secretory cells, two pairs of which are rich in chloroplasts, and a pair each of stalk cells and basal cells. The cuticle of the six secretory cells forms a subcuticular sac on the top of the trichome and is thought to function as a storage compartment for secondary metabolites (Olsson et al, 2009). The filamentous trichomes, on the other hand, are made up of five cells that are arranged in a T-shape, of which the top is formed by one elongated cell and the remaining four cells form the stalk ( Figure 1A) (Soetaert et al, 2013).…”

“…Artemisia annua (sweet wormwood) is a well-known species of this genus and accumulates several phytochemicals, including flavonoids, coumarins, monoterpenoids, sesquiterpenoids, diterpenoids, triterpenoids, steroids, lipids, and aliphatic compounds (Bhakuni et al, 2001). A. annua is most extensively studied for its inherent ability to accumulate the antimalarial sesquiterpene lactone artemisinin, which is synthesized and stored in epidermal appendages, called glandular trichomes, on the aerial parts of the plant (Olsson et al, 2009). …”

Bidirectional Secretions from Glandular Trichomes of Pyrethrum Enable Immunization of Seedlings

“…Previous research by Brodelius and coworkers (Olsson et al, 2009;Olofsson et al, 2012) provided evidence that sesquiterpene and monoterpene production may to some extent be divided between apical and subapical cells of Artemisia annua glandular trichomes. The evidence so far suggests that artemisinin biosynthesis genes are expressed in both layers (Olofsson et al, 2012).…”

“…The evidence so far suggests that artemisinin biosynthesis genes are expressed in both layers (Olofsson et al, 2012). However, germacrene A synthase (germacrene A is a precursor of STLs in pyrethrum) has been only detected in chloroplast-free apical cells (Olofsson et al, 2012), and 1-deoxy-D-xylulose-5-phosphate reductoisomerase participating in the plastidial MEP pathway and linalool synthase were amplified only from the chloroplast-containing subapical cells (Olsson et al, 2009;Olofsson et al, 2012). A. annua trichomes have an additional stalk cell layer compared with pyrethrum glandular trichomes, but otherwise they are phenotypically very similar (Duke and Paul, 1993).…”