Genomics and Applied Biology 2024, Vol.15, No.5, 223-234 http://bioscipublisher.com/index.php/gab 224 Despite the progress in genome sequencing, current assemblies of the cannabis genome remain incomplete, with significant portions unmapped or poorly annotated. This research aims to address these gaps by leveraging modern genomics technologies to provide a more comprehensive and high-resolution view of the cannabis genome. By integrating multi-omics approaches, including genomics, transcriptomics, and metabolomics, this study seeks to elucidate the complex genetic and biochemical pathways involved in cannabinoid and terpene biosynthesis. The ultimate goal is to facilitate the development of novel cannabis cultivars with optimized traits for medicinal, agricultural, and industrial applications, thereby enhancing the utility and economic value of this multifaceted plant. 2 Historical Background of Cannabis Genomic Studies 2.1 Early genetic studies of Cannabis The early genetic studies of Cannabis sativa L. primarily focused on its cultivation and use for various purposes, including fiber, oil, food, and medicinal properties. Cannabis has been cultivated throughout human history, and selective breeding has produced plants for specific uses, such as high-potency marijuana strains and hemp cultivars for fiber and seed production (Bakel et al., 2011). However, scientific research on cannabis was significantly restricted due to its classification as a narcotic under the Single Convention on Narcotic Drugs of 1961, which limited its production and supply except under license (Hurgobin et al., 2020). Despite these restrictions, early genetic studies laid the groundwork for understanding the basic biology and molecular mechanisms controlling key traits in cannabis. 2.2 Developments leading to genomic sequencing The relaxation of legislation governing cannabis cultivation for research, medicinal, and recreational purposes in certain jurisdictions has accelerated the development of modern genomics technologies applied to cannabis. This shift has enabled more comprehensive examinations of the cannabis genome, including the use of whole genome sequencing (WGS) and other omics-based methods (Hesami et al., 2020; Hurgobin et al., 2020). The first draft genome sequence of Cannabis sativa was reported using short-read sequencing approaches, providing a haploid genome sequence of 534 Mb and a transcriptome of 30 000 genes (Bakel et al., 2011). This development marked a significant milestone in cannabis genomic research, allowing for the systematic analysis of genes involved in cannabinoid biosynthesis and other traits of interest. 2.3 Key milestones in Cannabis genome research Several key milestones have been achieved in cannabis genome research, including the identification of specific genes and genetic variants associated with cannabinoid biosynthesis. For instance, the exclusive occurrence of Δ 9-tetrahydrocannabinolic acid synthase in marijuana strains and its replacement by cannabidiolic acid synthase in hemp cultivars explains the production of psychoactive THC in marijuana but not in hemp (Bakel et al., 2011). Additionally, recent advances in genome-wide sequencing techniques have enabled the identification of low-frequency genetic variants involved in cannabis dependence, highlighting the potential utility of WGS for understanding the genetic basis of cannabis use disorders (Gizer et al., 2018). Moreover, the application of multi-omics approaches has provided deeper insights into the molecular mechanisms underlying cannabis traits. These approaches have facilitated the identification of correlations between biological processes and metabolic pathways, aiding in the development of therapeutic marijuana strains with tailored cannabinoid profiles and improved agronomic characteristics (Sirangelo et al., 2022). The integration of genomics, transcriptomics, and metabolomics has thus become a powerful tool for advancing cannabis research and breeding programs. 3 Advancements in Cannabis Genome Sequencing 3.1 Major Cannabis genome sequencing projects Several significant projects have been undertaken to sequence the genome of Cannabis species. One notable project involved the sequencing of wild-type varieties of Cannabis sativa using PacBio single-molecule sequencing and Hi-C technology, resulting in a comprehensive de novo genome assembly (Gao et al., 2020).
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