The question of whether the common garden flower Cleome (spider flower) is related to hemp (Cannabis) stems from a recent biological discovery. Although these plants look entirely different and belong to separate botanical groups, scientists found an unexpected connection in their biochemical factories. This shared feature involves a highly specific metabolic process, suggesting a deeper link than their outward appearance implies. Understanding this relationship requires examining their classification and the specific internal processes they share.
Taxonomic Placement of Cleome and Hemp
Taxonomic classification shows that Cleome and Cannabis are distant relatives. Cleome belongs to the family Cleomaceae, which is part of the Order Brassicales, alongside plants like broccoli and mustard. In sharp contrast, Cannabis sativa (hemp) is classified within the Cannabaceae family. This family, which includes hops (Humulus), belongs to the entirely different Order Rosales. This placement establishes a clear separation, though both Orders belong to the larger group of flowering plants known as the Rosids, indicating a very ancient common ancestry.
The Shared Chemical Pathways
The scientific curiosity surrounding their relationship stems from the fact that both plants share a specific, complex chemical production method: prenylation. Prenylation is a biochemical modification where a plant attaches an isoprenoid group, typically derived from geranyl diphosphate (GPP), to a compound like a flavonoid or a fatty acid. In Cannabis, this process is fundamental to creating cannabinoids like cannabigerolic acid (CBGA), the precursor to compounds like THC and CBD. The Cannabis plant uses specialized aromatic prenyltransferase enzymes, such as CsPT1 and CsPT4, to catalyze the attachment of GPP to olivetolic acid.
This specific enzyme machinery is what allows Cannabis to synthesize its unique class of compounds. Research has shown that Cleome species also produce prenylated compounds, specifically a class of prenylated flavonoids, using a remarkably similar enzymatic logic. The enzymes in Cleome perform an equivalent prenylation reaction to produce their own unique metabolites, even though the final chemical product differs from a cannabinoid. This shared genetic programming for a complex biosynthetic step is a significant finding that suggests a common chemical heritage.
Evolutionary Relationship and Divergence
The shared prenylation pathway is a genetic trait retained from a distant ancestor despite millions of years of evolutionary separation. Since Cleome and Cannabis belong to different Orders (Rosales and Brassicales), their last common ancestor is extremely ancient, predating the origin of the Rosales Order around 101.6 million years ago. This deep evolutionary timeline suggests the ancestral plant already possessed the genetic instructions for creating these prenyltransferase enzymes. As the lineages diverged, the Cannabis line adapted this machinery to produce cannabinoids, while the Cleome line adapted it to produce prenylated flavonoids. The relationship is not one of close kinship, but one of shared, ancient biochemical technology.