Analysis of gene expression in PK tissues. (a) RNA-Seq read counts for 30,074 representative transcripts (rows), expressed as log2 RPKM, were subjected to hierarchical agglomerative clustering based on their expression pattern across tissues (columns). (b) Schematic illustration of THCA and CBDA cannabinoid biosynthesis, including the production of fatty acid and isoprenoid precursors via the hexanoate, MEP and GPP pathways. Hexanoate could arise through fatty acid degradation, involving desaturase, lipoxygenase (LOX) and hydroperoxide lyase (HPL) steps. Activation of hexanoate by an acyl-activating enzyme (AAE) yields hexanoyl-CoA, which is the substrate for the polyketide synthase enzyme (OLS) that forms olivetolic acid. The prenyl side-chain originates in the MEP pathway, which provides substrates for GPP synthesis, and is added by an aromatic prenyltransferase (PT) . The final steps are catalyzed by the oxidocyclases THCAS and CBDAS. Pathway enzymes and metabolic intermediates are indicated in black and blue, respectively. (c) Same data as (a), showing the expression levels for genes in the cannabinoid pathway and precursor pathways (rows) across the six assayed tissues (columns). The majority of the genes encoding cannabinoid and precursor pathway enzymes are most highly expressed in the flowering stages. Gene and pathway names correspond to those used in panel B.
van Bakel et al. Genome Biology 2011 12:R102 doi:10.1186/gb-2011-12-10-r102