The mint family of herbs, which includes sage, rosemary, basil, and even woody plants like teak, provide an invigorating jolt to our senses of smell and taste. Researchers from Michigan State University have found that these plants have diversified their specialized natural characteristics through the evolution of their chemistry, which could lead to potential future applications ranging from medicine to pesticide production.
“People easily recognize members of the mint family for their specialized metabolites,” said Björn Hamberger, associate professor and James K. Billman Jr., MD, endowed professor in the College of Natural Science. “Metabolites are an effective way for plants to defend themselves because they cannot run away. »
Since 2016, Hamberger has been studying specialized metabolites in plants called terpenoids, which are essential for protecting plants against predators and pathogens and are also common ingredients in green and sustainable agrochemicals, antioxidants, cosmetics and fragrances. .
Hamberger worked with Robin Buell, a former MSU genomics researcher now at the University of Georgia, who sequenced several mint plant genomes. This collaboration with Buell’s team led Hamberger graduate students Abigail Bryson and Emily Lanier to discover how multiple mint family genomes evolved and how these chemistries emerged over the past 60-70 million years. ‘years.
“Over millions of years, plants have adapted and evolved for their particular niches where they thrive, which means these chemistries are diverse and have clearly adapted to their environment,” Hamberger said. “So we’re trying to identify and discover the pathways to these specialized metabolites that plants make. »
Taking an interdisciplinary approach, Bryson identified the genomic organization of terpenoid biosynthesis and Lanier analyzed the chemical pathways. Together, Lanier and Bryson discovered something very unusual about the mint family’s beauty genome. It has a large group of biosynthetic genes. A BGC is a group of genes close to each other in the genome and involved in the same metabolic pathways. These genes are like individual beads in a necklace, separate yet connected. Additionally, Bryson and Lanier found variants of this BGC in six other species of the mint family.
“We’re learning that the physical location of genes in the genome matters,” Bryson said. “It can drive the evolution of specialized metabolic pathways in the plant, leading to a great diversity 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 that code for two distinct terpenoid pathways. The team found that these terpenoids accumulate in various parts of the plant, such as leaves and roots, and may play distinct roles in adaptation.
“It’s the same basic molecule, but each species makes its own version and modifies it in different ways to suit its survival needs,” Lanier said.
Hamberger describes it as a recipe that everyone has a copy of and modifies to suit their needs and preferences.
Previous research has led to unique medical uses for mint plants. For example, Indian Coleus can be used as a natural treatment for glaucoma and Texas sage is an effective natural antimicrobial against tuberculosis. The new molecular adaptations that Hamberger and his team have found open the door to future applications of natural plant products from the mint family.
“Our team has been excited about the opportunities within the mint family,” Hamberger said. “These mint enzymes, as in the American plant Beautyberry, give us the ability to make natural herbal products in the lab, including – hopefully in the future – natural mosquito repellents that smell good.” »