Tag: Trichomes

The hexanoyl-CoA precursor for cannabinoid biosynthesis is formed by an acylactivating enzyme in Cannabis sativa trichomes

Jake M Stout, Zakia Boubakir, Stephen J Ambrose, Jonathan E Page

February 2012 The Plant Journal 71(3):353-65 

DOI: 10.1111/j.1365-313X.2012.04949.x

The psychoactive and analgesic cannabinoids (e.g. Δ(9) -tetrahydrocannabinol (THC)) in Cannabis sativa are formed from the short-chain fatty acyl-coenzyme A (CoA) precursor hexanoyl-CoA. Cannabinoids are synthesized in glandular trichomes present mainly on female flowers. We quantified hexanoyl-CoA using LC-MS/MS and found levels of 15.5 pmol g(-1) fresh weight in female hemp flowers with lower amounts in leaves, stems and roots. This pattern parallels the accumulation of the end-product cannabinoid, cannabidiolic acid (CBDA). To search for the acyl-activating enzyme (AAE) that synthesizes hexanoyl-CoA from hexanoate, we analyzed the transcriptome of isolated glandular trichomes. We identified 11 unigenes that encoded putative AAEs including CsAAE1, which shows high transcript abundance in glandular trichomes. In vitro assays showed that recombinant CsAAE1 activates hexanoate and other short- and medium-chained fatty acids. This activity and the trichome-specific expression of CsAAE1 suggest that it is the hexanoyl-CoA synthetase that supplies the cannabinoid pathway. CsAAE3 encodes a peroxisomal enzyme that activates a variety of fatty acid substrates including hexanoate. Although phylogenetic analysis showed that CsAAE1 groups with peroxisomal AAEs, it lacked a peroxisome targeting sequence 1 (PTS1) and localized to the cytoplasm. We suggest that CsAAE1 may have been recruited to the cannabinoid pathway through the loss of its PTS1, thereby redirecting it to the cytoplasm. To probe the origin of hexanoate, we analyzed the trichome expressed sequence tag (EST) dataset for enzymes of fatty acid metabolism. The high abundance of transcripts that encode desaturases and a lipoxygenase suggests that hexanoate may be formed through a pathway that involves the oxygenation and breakdown of unsaturated fatty acids.
Abstract

Tetrahydrocannabinolic acid synthase, the enzyme controlling marijuana psychoactivity is secreted into the storage cavity of the glandular trichomes.

Supaart Sirikantaramas, Futoshi Taura, Yumi Tanaka, Yu Ishikawa, Satoshi Morimoto, Yukihiro Shoyama

Plant and Cell Physiology 46(9), 1578–1582.

DOI: 10.1093/pcp/pci166

Tetrahydrocannabinolic acid (THCA) synthase is the enzyme responsible for the production of tetrahydrocannabinol (THC), the psychoactive component of marijuana (Cannabis sativa L.). We suggest herein that THCA is biosynthesized in the storage cavity of the glandular trichomes based on the following observations. (i) The exclusive expression of THCA synthase was confirmed in the secretory cells of glandular trichomes by reverse transcription–PCR (RT–PCR) analysis. (ii) THCA synthase activity was detected in the storage cavity content. (iii) Transgenic tobacco expressing THCA synthase fused to green fluorescent protein showed fluorescence in the trichome head corresponding to the storage cavity. These results also showed that secretory cells of the glandular trichomes secrete not only metabolites but also biosynthetic enzyme.
Abstract

PKS Activities and Biosynthesis of Cannabinoids and Flavonoids in Cannabis sativa L. Plants

Isvett Josefina Flores-Sanchez and Robert Verpoorte

Plant Cell Physiol (2008) 49 (12): 1767-1782.

doi: 10.1093/pcp/pcn150

Polyketide synthase (PKS) enzymatic activities were analyzed in crude protein extracts from cannabis plant tissues. Chalcone synthase (CHS, EC 2.3.1.74), stilbene synthase (STS, EC 2.3.1.95), phlorisovalerophenone synthase (VPS, EC 2.3.1.156), isobutyrophenone synthase (BUS) and olivetol synthase activities were detected during the development and growth of glandular trichomes on bracts. Cannabinoid biosynthesis and accumulation take place in these glandular trichomes. In the biosynthesis of the first precursor of cannabinoids, olivetolic acid, a PKS could be involved; however, no activity for an olivetolic acid-forming PKS was detected. Content analyses of cannabinoids and flavonoids, two secondary metabolites present in this plant, from plant tissues revealed differences in their distribution, suggesting a diverse regulatory control for these biosynthetic fluxes in the plant.
Abstract