Family of ancient plants, new medicine
The mint family, also known as the mint family, is a diverse group of herbs that are widely used for culinary, medicinal, and ornamental purposes. The family contains over 7,000 species, including popular herbs such as basil, rosemary, thyme, mint, and sage.
The mint herb family, including sage, rosemary, basil, and even woody plants such as teak, provides a stimulating effect on our sense of smell and taste. Researchers at Michigan State University have found that the evolution of these plants has diversified their special natural characteristics through the evolution of their chemical composition, opening up the possibility of future uses in fields such as medicine and pesticide production.
“People easily recognize members of the mint family by their specialized metabolites,” said Bjorn Hamberger, associate professor, and James C. Billman, Jr., MD, professor at the College of Natural Sciences. “Metabolites are an effective way to protect plants because they can’t escape.”
Since 2016, Hamberger has been studying specialized plant metabolites called terpenoids, which are essential for protecting plants from predators and pathogens, and are common ingredients in sustainable agrochemicals, antioxidants, cosmetics, and fragrances.
Hamberger worked with Robin Buell, a former MSU genomics researcher now at the University of Georgia, who sequenced the genomes of several mint plants. This collaboration with Buell’s team led Hamberger’s graduate students, Abigail Bryson and Emily Lanier, to the discovery of how several genomes of the mint family have evolved and how these chemical processes have evolved over the past 60–70 million years.
“Over millions of years, plants have adapted and evolved for their specific niches in which they thrive, meaning these chemicals are diverse and have clearly adapted to their environment,” Hamberger said. “So we’re trying to identify and open pathways to these specialized metabolites that plants make.”
Using an interdisciplinary approach, Bryson determined the genomic organization of terpenoid biosynthesis, while Lanier analyzed the chemical pathways. Together, Lanier and Bryson discovered something very unusual in the genome of the beautyberry from the mint family. It has a large biosynthetic gene cluster. BGC is a group of genes located close to each other in the genome and participating in the same metabolic pathways. These genes are like individual pearls on a necklace—separated and yet connected. In addition, Bryson and Lanier found variants of this BGC in six other mint species.
“We’re learning that the physical location of genes in the genome is important,” Bryson said. “It can stimulate the evolution of specialized metabolic pathways in the plant, leading to a huge variety of interesting natural plant compounds.”
BGCs are well known in the bacterial world, but their role in plants is not fully understood. The BGC cluster of the beautyberry plant contains genes encoding two distinct terpenoid pathways. The team found that these terpenoids accumulate in different parts of the plant, such as leaves and roots, and may play different roles in adaptation.
“It’s the same basic molecule, but each species creates its own version and modifies it differently to suit their survival needs,” Lanier said.
Hamberger describes it as a recipe that everyone has a copy of and can modify according to their requirements and preferences.
Previous research has led to the unique medicinal uses of mint plants. For example, Indian coleus can be used as a natural treatment for glaucoma, and Texas sage is a natural antimicrobial effective against tuberculosis. The new molecular adaptations that Hamberger and his team have discovered open the door to future uses for natural herbal products in the mint family.
“Our team was excited about the capabilities of the mint family,” Hamberger said. “These mint enzymes, as found in the American beautyberry plant, give us the ability to make herbal products in the lab, including—hopefully in the future—natural, good-smelling mosquito repellants.”
Reference: “Discovery of Miltiradiene Biosynthesis Gene Cluster in Lamiaceae Reveals Dynamic Evolutionary Trajectory” Abigail E. Bryson, Emily R. Lanier, Keane H. Lau, John P. Hamilton, Brianna Vaylancourt, Davis Mathieu, Alan E. Yokka, Garrett P. Miller , Patrick P. Edger, C. Robin Buell, and Bjorn Hamberger, January 20, 2023, Nature Communications.
DOI: 10.1038/s41467-023-35845-1
