Researchers used a virus-based CRISPR system to precisely edit the gatekeeper enzyme HMGR in petunias and lettuce, effectively unlocking a natural metabolic “brake” that restricts scent and nutrient production. By fine-tuning this regulatory control rather than disabling the gene entirely, they enabled plants to channel more energy into producing aromatic compounds and health-promoting antioxidants. The result was more vigorous growth, stronger floral fragrance, and enhanced nutritional value. Importantly, because no foreign DNA was introduced, this transgene-free approach offers a powerful new framework for developing higher-quality, nutrient-enriched crops through precision gene editing.

Scientists have long sought to understand why some plants are fragrant powerhouses while others remain subtle. Now, a research team from the Hebrew University of Jerusalem has cracked a genetic "bottleneck," using precision gene editing to boost the scent of flowers and the nutritional profile of vegetables.

The study, led by Dr. Oded Skaliter and Prof. Alexander Vainstein from the Institute of Plant Sciences and Genetics in Agriculture at the Hebrew University of Jerusalem, focused on a specific enzyme called HMGR. This enzyme acts as a biological gatekeeper for the production of terpenoids, the largest group of natural compounds in plants. Terpenoids are responsible for everything from plant defense, the sweet smell of a rose, the striking colors of fruits, to the medicinal properties of anti-malarial drugs.

Breaking the Genetic Brake
In nature, plants have a built-in system to prevent themselves from overproducing certain metabolites. The HMGR enzyme has a specific regulatory domain that acts like a metabolic brake. When the plant senses it has enough terpenoids, this domain shuts down HMGR to stop terpenoids production and save energy.

Using a virus based CRISPR/Cas9 system, the researchers targeted this regulatory region in petunias and lettuce. By subtly editing the genetic code rather than completely knocking out the gene, they were able to disable the "brake" without harming the plant’s health.

"These results establish a transgene free strategy to enhance the production of natural compounds, like volatiles and pigments" said Prof. Alexander Vainstein. "Our work provides a framework for developing resilient, nutrient enriched crops that can meet both agricultural and consumer needs".

The results were striking. The edited petunias did not just smell stronger; they were more vigorous, and grew larger flowers.

A Surprising Connection

One of the most unexpected findings was that editing the terpenoid pathway also boosted a completely different group of metabolites called phenylpropanoids. These compounds are responsible for the spicy and floral notes in many scents, such as the smell of almonds or cloves.

"We found that the induced mutations alleviated the negative feedback regulation of the enzyme," explained Dr. Oded Skaliter. "This reveals a complex layer of interaction between metabolic pathways, showing how we can use precision breeding to improve the sensory qualities of plants".

By analyzing the plant’s internal chemistry, the team discovered that the genetic edit caused a "carbon shift". Because the terpenoid pathway was working more efficiently, the plant began producing more raw carbon, which then flowed into other scent and health related pathways.

From Better Flowers to Healthy Salads
The researchers applied the same logic to lettuce, a crop known for its crunch but often criticized for its low nutritional density. The edited lettuce showed increased levels of sesquiterpenes and apocarotenoids, which contribute to flavor and antioxidant activity.

This "transgene free" strategy is particularly important for the future of agriculture. Because the final plants do not contain foreign DNA, they offer a precise alternative for metabolic engineering that may gain better consumer acceptance than traditional GMOs.