Delineating genetic regulation of cannabinoid biosynthesis during female flower development in Cannabis sativa

Building a biofactory: Constructing glandular trichomes in Cannabis sativa

Flowers of Cannabis sativa L. are densely covered with glandular trichomes containing cannabis resin that is used for medicinal and recreational purposes. The highly productive glandular trichomes have been described as 'biofactories.' In this review, we use this analogy to highlight recent advances in cannabis cell biology, metabolomics, and transcriptomics. The biofactory is built by epidermal outgrowths that differentiate into peltate-like glandular trichome heads, consisting of a disc of interconnected secretory cells with unique cellular structures. Cannabinoid and terpenoid products are warehoused in the extracellular storage cavity. Finally, multicellular stalks raise the glandular heads above the epidermis, giving cannabis flower their frosty appearance.

Advancement of Research Progress on Synthesis Mechanism of Cannabidiol (CBD)

Cannabis sativa L. is a multipurpose crop with high value for food, textiles, and other industries. Its secondary metabolites, including cannabidiol (CBD), have potential for broad application in medicine. With the CBD market expanding, traditional production may not be sufficient. Here we review the potential for the production of CBD using biotechnology. We describe the chemical and biological synthesis of cannabinoids, the associated enzymes, and the application of metabolic engineering, synthetic biology, and heterologous expression to increasing production of CBD.

Assessing the adaptive role of cannabidiol (CBD) in Cannabis sativa defense against cannabis aphids

Cannabis sativa is known for having unique specialized or secondary metabolites, cannabinoids that are derived from an extension of the terpene pathway in the Cannabis lineage and includes more than 100 other similar metabolites. Despite the assumption that cannabinoids evolved as novel herbivory defense adaptations, there is limited research addressing the role of cannabinoids in C. sativa responses to insect herbivores. Here we investigated the role of cannabidiol (CBD), the predominant cannabinoid in hemp, in plant defense against cannabis aphid (Phorodon cannabis), one of the most damaging pests of hemp. We hypothesize that insect feeding may induce changes in cannabinoids as an adaptive strategy for defense. We found that mean fecundity, net reproductive rate (R0) and adult longevity of cannabis aphids was reduced on the high cannabinoid cultivar compared to the low- cannabinoid cultivar in whole plant assays. In contrast, supplementation of CBD in artificial feeding assays increased aphid fecundity from day 1 to day 3. Additionally, aphid feeding did not impact cannabinoid levels in leaf tissues with the exception of Δ9-tetrahydrocannabinol (THC). This suggests that other cannabinoids and/or metabolites such as terpenes are causing the observed decrease in aphid performance in the whole plant assays. In addition to cannabinoids, C. sativa also possesses a range of defense mechanisms via phytohormone signaling pathways that are well described in other plant species. Indeed, cannabis aphid feeding significantly increased levels of the major phytohormones, salicylic acid, jasmonic acid, and abscisic acid, which are known to be involved in plant defense responses against aphid species. These results highlight the interplay between cannabinoid synthesis and phytohormone pathways and necessitate further investigation into this complex interaction.

Phytocannabinoids biosynthesis during early stages of development of young Cannabis sativa L. seedlings: Integrating biochemical and transcription data

Cannabis sativa (L.) is characterized by great genetic and phenotypic diversity, also expressed in the array of bioactive compounds synthesized. Despite its great potential economic interest, knowledge of the biology and genetics of this crop is incomplete, and still many efforts are needed for a complete understanding of the molecular mechanisms regulating its key traits. To better understand the synthesis of these compounds, we analysed the transcription levels of cannabinoid pathway genes during early phases of plant development, then comparing the transcriptional results with a chemical characterization of the same samples. The work was conducted on both industrial and medicinal C. sativa plants, using samples belonging to three different chemotypes. Genes coding for the cannabinoid synthases, involved in the last step of the cannabinoid biosynthetic pathway, were found to be already expressed in the seed, providing a measure of the importance of this metabolism for the plant. Cannabichromenic acid is known as the first cannabinoid accumulating in the seedlings, shortly after emergence, and it was found that there is a good correspondence between transcript accumulation of the cannabichromenic acid synthase gene and accumulation of the corresponding metabolite.

Cannabis sativa: origin and history, glandular trichome development, and cannabinoid biosynthesis

Is Cannabis a boon or bane? Cannabis sativa has long been a versatile crop for fiber extraction (industrial hemp), traditional Chinese medicine (hemp seeds), and recreational drugs (marijuana). Cannabis faced global prohibition in the twentieth century because of the psychoactive properties of ∆9-tetrahydrocannabinol; however, recently, the perspective has changed with the recognition of additional therapeutic values, particularly the pharmacological potential of cannabidiol. A comprehensive understanding of the underlying mechanism of cannabinoid biosynthesis is necessary to cultivate and promote globally the medicinal application of Cannabis resources. Here, we comprehensively review the historical usage of Cannabis, biosynthesis of trichome-specific cannabinoids, regulatory network of trichome development, and synthetic biology of cannabinoids. This review provides valuable insights into the efficient biosynthesis and green production of cannabinoids, and the development and utilization of novel Cannabis varieties.

Cadmium exposure is associated with increased transcript abundance of multiple heavy metal associated transporter genes in roots of hemp (Cannabis sativa L.)

Industrial hemp (Cannabis sativa L.) has demonstrated promise for phytoremediation due to an extensive root system, large biomass, and ability to survive under relatively high levels of heavy metals. However, little research has been conducted to determine the impact of heavy metal uptake in hemp grown for medicinal use. This study evaluated the potential for cadmium (Cd) uptake and its impact on growth, physiological responses, and transcript expression of metal transporter genes in a hemp variety grown for flower production. The cultivar 'Purple Tiger' was exposed to 0, 2.5, 10, and 25 mg·L^-1 Cd in a greenhouse hydroponic study in two independent experiments. Plants exposed to 25 mg·L^-1 Cd displayed stunted plant growth characteristics, reduced photochemical efficiency, and premature senescence suggesting Cd toxicity. At the two lower concentrations of Cd (2.5 and 10 mg·L^-1 Cd), plant height, biomass, and photochemical efficiency were not affected, with chlorophyll content index (CCI) being slightly lower at 10 mg·L^-1 Cd, compared to 2.5 mg·L^-1 Cd. There were no consistent differences between the two experiments in total cannabidiol (CDB) and tetrahydrocannabinol (THC) concentrations in flower tissues at 2.5 and 10 mg·L^-1 Cd, compared to the control treatment. Root tissue accumulated the highest amount of Cd compared to other tissues for all the Cd treatments, suggesting preferential root sequestration of this heavy metal in hemp. Transcript abundance analysis of heavy metal-associated (HMA) transporter genes suggested that all seven members of this gene family are expressed in hemp, albeit with higher expression in the roots than in the leaves. In roots, CsHMA3 was up-regulated at 45 and 68 d after treatment (DAT), and CsHMA1, CsHMA4, and CsHMA5 were upregulated only under long term Cd stress at 68 DAT, at 10 mg·L^-1 Cd. Results suggest that expression of multiple HMA transporter genes in the root tissue may be upregulated in hemp exposed to 10 mg·L^-1 Cd in a nutrient solution. These transporters could be involved in Cd uptake in the roots via regulating its transport and sequestration, and xylem loading for long distance transport of Cd to shoot, leaf, and flower tissues.

Hormonal control of promoter activities of Cannabis sativa prenyltransferase 1 and 4 and salicylic acid mediated regulation of cannabinoid biosynthesis

Cannabis sativa aromatic prenyltransferase 4 (CsPT4) and 1 (CsPT1) have been shown to catalyze cannabigerolic acid (CBGA) biosynthesis, a step that rate-limits the cannabinoid biosynthetic pathway; both genes are highly expressed in flowers. CsPT4 and CsPT1 promoter driven β-glucuronidase (GUS) activities were detected in leaves of cannabis seedlings, and strong CsPT4 promoter activities were associated with glandular trichomes. Hormonal regulation of cannabinoid biosynthetic genes is poorly understood. An in silico analysis of the promoters identified putative hormone responsive elements. Our work examines hormone-responsive elements in the promoters of CsPT4 and CsPT1 in the context of physiological responses of the pathway to the hormone in planta. Dual luciferase assays confirmed the regulation of promoter activities by the hormones. Further studies with salicylic acid (SA) demonstrated that SA pretreatment increased the expression of genes located downstream of the cannabinoid biosynthetic pathway. The results from all aspects of this study demonstrated an interaction between certain hormones and cannabinoid synthesis. The work provides information relevant to plant biology, as we present evidence demonstrating correlations between molecular mechanisms that regulate gene expression and influence plant chemotypes.

Metabolomic analysis of methyl jasmonate treatment on phytocannabinoid production in Cannabis sativa

Cannabis sativa is a multi-use and chemically complex plant which is utilized for food, fiber, and medicine. Plants produce a class of psychoactive and medicinally important specialized metabolites referred to as phytocannabinoids (PCs). The phytohormone methyl jasmonate (MeJA) is a naturally occurring methyl ester of jasmonic acid and a product of oxylipin biosynthesis which initiates and regulates the biosynthesis of a broad range of specialized metabolites across a number of diverse plant lineages. While the effects of exogenous MeJA application on PC production has been reported, treatments have been constrained to a narrow molar range and to the targeted analysis of a small number of compounds. Using high-resolution mass spectrometry with data-dependent acquisition, we examined the global metabolomic effects of MeJA in C. sativa to explore oxylipin-mediated regulation of PC biosynthesis and accumulation. A dose-response relationship was observed, with an almost two-fold increase in PC content found in inflorescences of female clones treated with 15 mM MeJA compared to the control group. Comparison of the inflorescence metabolome across MeJA treatments coupled with targeted transcript analysis was used to elucidate key regulatory components contributing to PC production and metabolism more broadly. Revealing these biological signatures improves our understanding of the role of the oxylipin pathway in C. sativa and provides putative molecular targets for the metabolic engineering and optimization of chemical phenotype for medicinal and industrial end-uses.

Exogenous application of stress-related signaling molecules affect growth and cannabinoid accumulation in medical cannabis (Cannabis sativa L.)

Medical cannabis (Cannabis sativa L.) is a source of bioactive phytochemicals with promising pharmacological and therapeutic applications. Enhancing the accumulation of valuable bioactive compounds is potentially a way of increasing the economic importance of this crop. Signaling molecules like salicylic acid (SA), jasmonic acid (JA), and γ-aminobutyric acid (GABA) are involved in the regulation of plant development and responses to biotic and abiotic stresses. Moreover, several phytohormones regulate plant trichome formation and elicit the synthesis of secondary metabolites in many plant species in both in vitro and in vivo systems. Therefore, exogenously delivered plant signaling molecules have the potential to modify the chemical profiles of medical cannabis. In this study, we found that the foliar application of SA, methyl jasmonate (MeJA), and GABA produces changes in the accumulation of the two major cannabinoids, cannabidiolic acid (CBDA) and Δ⁹- tetrahydrocannabinolic acid (THCA), in leaves and inflorescences of a medical cannabis variety. MeJA at 0.1 mM increased the CBDA content in inflorescences by 15.6%, while SA and MeJA at 0.1 mM increased CBDA and THCA accumulation in leaves by up to 57.3%. Treatments did not change the expression of genes participating in the final steps of the biosynthetic pathway of cannabinoids: olivetolic acid cyclase (CsOAC-1 and CsOAC-2), 2-acylphloroglucinol 4-prenyltransferase (CsPT4), cannabidiolic acid synthase (CsCBDAS), and tetrahydrocannabinolic acid synthase (CsTHCAS). Trichome density was not significantly different from the control plants in any treatment. Besides, we found strong correlations between several plant growth parameters and cannabinoid yields, showing a direct link between plant fitness and the production of cannabinoids.