## 2 Biochemistry and Genetic Regulation of Aroma and Flavor Compounds in _C. sativa_ L.
### Terpenes  
Terpenes are the most prominent contributors to the aroma of cannabis, with over 100 distinct compounds identified across multiple cannabis varieties [13; 49]. As volatile compounds derived from the plant's secondary metabolism, terpenes define many of the distinctive aromas associated with cannabis [13]. Terpenes are synthesized via two main pathways: the mevalonate (MVA) pathway in the cell cytoplasm and the methylerythnitol phosphate (MEP) pathway in plastids [5; 48] (Figure 1). These pathways produce the isopenoid precursors dimethylallyl pyrophosphate and isopentenyl pyrophosphate, which  
Figure 1: Interconnections of biosynthesis pathways of _Camabis sativa_ L. aroma and flavor compounds. The polyketide, MEP, MEV, and phenylpropanol pathways are represented and comprehensive biosynthetic steps, as well as compounds, are included. CBC, cannabinoid; CBG, cannabinoid; CBGA, cannabinoid; CBGA, cannabinoid; acid; CoA, coenzyme A; DMAPP, dimethylallyl pyrophosphate; FFP, famesyl diphosphate; GPP, geranyl diphosphate; IPP, isopentenyl diphosphate; MEP, methylerythnitol phosphate; MVA, mevalonate; TPS, terpene synthase; VSC, volatile sulfur compound. Adapted and synthesized from: [PERSON] et al., 2020 [5]; [PERSON] et al., 2019 [46]; [PERSON] et al., 2019 [47]; and [PERSON], 2008 [48]. combine to form geranyl pyrophosphate (GPP), the key precursor for monoterpenes [46; 48]. Sesquietrepenes, such as cryophyllene and humulene, are derived from farnesyl pyrophosphate (FPP), an elongated product of GPP [50]. The diversity of terpen in cannabis is attributed to the activity of terpene synthase (TPS) enzymes, which catalyze the conversion of GPP and FPP into various terpene structures [5; 46]. The _C. sativa_ L. genome encodes a diverse array of TPS enzymes, with at least 30 functional TPS genes identified [47]. In 2019, [PERSON] et al. described 55 TPSs with a genomic context and tissue-specific expression, highlighting the diversity of the TPS family in cannabis [50]. TPS enzymes are classified into different subfamilies based on their phylogenetic relationships and functional roles. This enzymatic diversity allows for the generation of over 140 different terpen in cannabis, creating a vast array of aromatic combinations [5]. Collectively, studies have demonstrated that the TPS gene family in cannabis is quite diverse, with different enzymes responsible for producing the wide array of terpenes found in cannabis resin. The expression of these genes varies between different tissues, developmental stages, and cultivars, contributing to the unique terpene profiles observed in different cannabis strains [51]. Understanding the genomic underpinnings and biochemical mechanisms of terpene biosynthesis in cannabis provides valuable insights for breeding programs aimed at developing strains with specific aroma profiles or medicinal properties. However, recent analyses of commercial cannabis samples suggest that the terpene diversity in the current germplasm may be limited, highlighting the need for the further exploration and characterization of cannabis' genetic resources [46; 50]. The most prevalent terpenes in cannabis include myrcene, which has a musky, earthy, and fruity fragrance and is associated with relaxant, sedative, anti-inflammatory, and analgesic effects [52; 53]. \(\alpha\)- and \(\beta\)-Limonene emit a citrus aroma reminiscent of lemons and oranges and are linked to mood elevation, stress relief, and potential neuroprotective benefits [54; 55]. \(\alpha\)-Pinene has a piney scent similar to coniferous trees and may support brain health and possess anti-inflammatory properties [56; 57]. Linalool is characterized by its floral, lavelander-like scent and is associated with relaxation and stress reduction [56; 58]. \(\beta\)-Caryophyllene has a peppery aroma akin to black pepper and cloves and displays neuroprotective and antioxidant properties [59; 60]. Humulene has an earthy, woody aroma and has been investigated for potential anti-inflammatory effects [61].