During the last decade, the use of medical Cannabis has expanded globally and legislation is getting more liberal in many countries, facilitating the research on cannabinoids. The unique interaction of cannabinoids with the human endocannabinoid system makes these compounds an interesting target to be studied as therapeutic agents for the treatment of several medical conditions. However, currently there are important limitations in the study, production and use of cannabinoids as pharmaceutical drugs. Besides the main constituent tetrahydrocannabinolic acid, the structurally related compound cannabidiol is of high interest as drug candidate. From the more than 100 known cannabinoids reported, most can only be extracted in very low amounts and their pharmacological profile has not been determined. Today, cannabinoids are isolated from the strictly regulated Cannabis plant, and the supply of compounds with sufficient quality is a major problem. Biotechnological production could be an attractive alternative mode of production. Herein, we explore the potential use of synthetic biology as an alternative strategy for synthesis of cannabinoids in heterologous hosts. We summarize the current knowledge surrounding cannabinoids biosynthesis and present a comprehensive description of the key steps of the genuine and artificial pathway, systems biotechnology needs and platform optimization.

Phytocannabinoids are a group of plant-derived metabolites that display a wide range of psychoactive as well as health-promoting effects. The production of pharmaceutically relevant cannabinoids relies on extraction and purification from cannabis (Cannabis sativa) plants yielding the major constituents, Δ9-tetrahydrocannabinol and cannabidiol. Heterologous biosynthesis of cannabinoids in Nicotiana benthamiana or Saccharomyces cerevisiae may provide cost-efficient and rapid future production platforms to acquire pure and high quantities of both the major and the rare cannabinoids as well as novel derivatives. Here, we used a meta-transcriptomic analysis of cannabis to identify genes for aromatic prenyltransferases of the UbiA superfamily and chalcone isomerase-like (CHIL) proteins. Among the aromatic prenyltransferases, CsaPT4 showed CBGAS activity in both N. benthamiana and S. cerevisiae. Coexpression of selected CsaPT pairs and of CHIL proteins encoding genes with CsaPT4 did not affect CBGAS catalytic efficiency. In a screen of different plant UDP-glycosyltransferases, Stevia rebaudiana SrUGT71E1 and Oryza sativa OsUGT5 were found to glucosylate olivetolic acid, cannabigerolic acid, and Δ9-tetrahydrocannabinolic acid. Metabolic engineering of N. benthamiana for production of cannabinoids revealed intrinsic glucosylation of olivetolic acid and cannabigerolic acid. S. cerevisiae was engineered to produce olivetolic acid glucoside and cannabigerolic acid glucoside.

BackgroundRecent advances in synthetic biology have provided tools to efficiently construct complex DNA molecules which are an important part of many molecular biology and biotechnology projects. The planning of such constructs has traditionally been done manually using a DNA sequence editor which becomes error-prone as scale and complexity of the construction increase. A human-readable formal description of cloning and assembly strategies, which also allows for automatic computer simulation and verification, would therefore be a valuable tool.ResultsWe have developed pydna, an extensible, free and open source Python library for simulating basic molecular biology DNA unit operations such as restriction digestion, ligation, PCR, primer design, Gibson assembly and homologous recombination. A cloning strategy expressed as a pydna script provides a description that is complete, unambiguous and stable. Execution of the script automatically yields the sequence of the final molecule(s) and that of any intermediate constructs. Pydna has been designed to be understandable for biologists with limited programming skills by providing interfaces that are semantically similar to the description of molecular biology unit operations found in literature.ConclusionsPydna simplifies both the planning and sharing of cloning strategies and is especially useful for complex or combinatorial DNA molecule construction. An important difference compared to existing tools with similar goals is the use of Python instead of a specifically constructed language, providing a simulation environment that is more flexible and extensible by the user.Electronic supplementary materialThe online version of this article (doi:10.1186/s12859-015-0544-x) contains supplementary material, which is available to authorized users.

The kanMX4 resistance marker is widely used for Saccharomyces cerevisiae gene deletion and has been used to create a genome-wide deletion mutant collection. Transfer of PCR-amplified marker loci from collection mutants is a very efficient way of introducing mutations into other S. cerevisiae strains of interest. An important limitation of this strategy is that the kanMX4 marker is not easily removed, impairing the construction of multiple gene deletion strains. The MX4blaster is a novel MX4-compatible cassette that facilitates clean or scarless kanMX4 removal. The MX4blaster cassette efficiently replaces the kanMX4 cassette due to shared promoter and terminator sequences. The MX4blaster cassette is removed by the induction of an internal double-stranded break and transformation with a DNA fragment designed to recombine on either side of the cassette in combination with counter selection. Simple and inexpensive media are used for induction and counter selection, mitigating the use of expensive chemicals. Routinely, thirty percent of transformants successfully removed the MX4blaster cassette. The resulting mutants contain no trace of the MX4blaster cassette. The unique properties of the MX4blaster cassette make it an important addition to S. cerevisiae genetic tools, especially in combination with the genome-wide deletion collection.

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