Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada.
Anandia Laboratories Inc., Vancouver, British Columbia, Canada.
Plant J. 2020 Jan;101(1):37-56. doi: 10.1111/tpj.14516. Epub 2019 Oct 12.
The cannabis leaf is iconic, but it is the flowers of cannabis that are consumed for the psychoactive and medicinal effects of their specialized metabolites. Cannabinoid metabolites, together with terpenes, are produced in glandular trichomes. Superficially, stalked and sessile trichomes in cannabis only differ in size and whether they have a stalk. The objectives of this study were: to define each trichome type using patterns of autofluorescence and secretory cell numbers, to test the hypothesis that stalked trichomes develop from sessile-like precursors, and to test whether metabolic specialization occurs in cannabis glandular trichomes. A two-photon microscopy technique using glandular trichome intrinsic autofluorescence was developed which demonstrated that stalked glandular trichomes possessed blue autofluorescence correlated with high cannabinoid levels. These stalked trichomes had 12-16 secretory disc cells and strongly monoterpene-dominant terpene profiles. In contrast, sessile trichomes on mature flowers and vegetative leaves possessed red-shifted autofluorescence, eight secretory disc cells and less monoterpene-dominant terpene profiles. Moreover, intrinsic autofluorescence patterns and disc cell numbers supported a developmental model where stalked trichomes develop from apparently sessile trichomes. Transcriptomes of isolated floral trichomes revealed strong expression of cannabinoid and terpene biosynthetic genes, as well as uncharacterized genes highly co-expressed with CBDA synthase. Identification and characterization of two previously unknown and highly expressed monoterpene synthases highlighted the metabolic specialization of stalked trichomes for monoterpene production. These unique properties and highly expressed genes of cannabis trichomes determine the medicinal, psychoactive and sensory properties of cannabis products.
大麻叶是标志性的，但大麻的花朵被消耗，是因为其特殊代谢物具有致幻和药用作用。大麻素代谢物与萜烯一起，在腺毛状的表皮细胞中产生。从表面上看，大麻中的有柄和无柄表皮细胞仅在大小和是否有柄上有所不同。本研究的目的是：使用自发荧光和分泌细胞数量的模式来定义每种表皮细胞类型，检验有柄表皮细胞由无柄样前体发育而来的假说，并检验大麻腺毛状表皮细胞是否存在代谢特化。开发了一种使用表皮细胞固有自发荧光的双光子显微镜技术，该技术表明，有柄腺毛状表皮细胞具有与高大麻素水平相关的蓝色自发荧光。这些有柄表皮细胞具有 12-16 个分泌盘细胞，且萜烯特征以单萜烯为主。相比之下，成熟花朵和营养叶上的无柄表皮细胞具有红移自发荧光、8 个分泌盘细胞和萜烯特征以单萜烯为主。此外，自发荧光模式和盘细胞数量支持一个发育模型，即有柄表皮细胞由无柄表皮细胞发育而来。分离的花表皮细胞的转录组揭示了强烈表达大麻素和萜烯生物合成基因，以及与 CBDA 合酶高度共表达的未鉴定基因。鉴定和表征两个以前未知的高度表达的单萜合酶，突出了有柄表皮细胞对单萜烯生产的代谢特化。这些大麻表皮细胞的独特特性和高度表达的基因决定了大麻产品的药用、致幻和感官特性。
