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Catnip Crazed

By comparing the catnip genome to other plants along with other analyses, researchers have examined how catnip began to produce the enzyme that sends cats into a state of ecstasy, HealthDay reports.

This effect of catnip has been traced to the iridoid nepetalactone. While other plants in the mint family (Lamiaceae) produce iridoids — which repel insects — ancestors of the Nepetoideae arm of the family, which includes catnip, lost the ability to produce them, only to have it re-emerge in catnip (Nepeta). To examine this, an international team of researchers sequenced two species of catnip that produce iridoids, N. cataria L. and N. mussinii Spreng. ex. Henckel, and a closely related hyssop (Hyssopus officinalis L.) that does not produce an iridoid. 

As they report in Science Advances this week, researchers led by the Max Planck Institute for Chemical Ecology's Sarah O'Connor found that the loss of iridoids in Nepetoideae is due to the loss of the ISY gene. But Nepeta re-evolved a version of that gene and regained the ability to synthesize iridoids. "The evolution of nepetalactone biosynthesis in Nepeta is not simply a re-emergence of iridoid biosynthesis in this lineage; it also represents an evolutionary innovation," she and her colleagues write in their paper. "Nepetalactone is an example of repeated evolution with a twist; while nepetalactones maintain the iridoid structure, there are key differences compared to other iridoids found in the mint family."