In a new study, Weizmann Institute of Science scientists revealed the chain of biochemical reactions responsible for the production of saponins in plants, and discovered that it includes a surprising case of molecular "hijacking". The scientists even recorded an achievement in the field of synthetic biology: they restored the chain in its entirety through genetic engineering
We have soap and water, and plants have saponins - foaming, soap-like substances that probably help them fight pests by dissolving their fatty membranes. Saponins of plant origin are used in industry for various purposes - from the traditional production of shampoo and soap to the modern production of medicines, vaccines and even a low-calorie sweetener 1,000 times sweeter than regular sugar.
Despite the extensive use of these materials, it was not known until now how they are formed. BNew research Weizmann Institute of Science scientists revealed the chain of biochemical reactions responsible for the production of saponins in plants, and discovered that it includes a surprising case of molecular "hijacking". The scientists even recorded an achievement in the field of synthetic biology: they restored the chain in its entirety through genetic engineering and created saponins in a tobacco-like plant and in yeast. These findings open the door to the biochemical production of effective saponins for use in industry and agriculture.
Postdoctoral researcher Dr. Adam Jozwiak and other members of his group Prof. Assaf Aharoni The Department of Plant and Environmental Sciences set out to find out how saponins are formed in spinach, which was found to be particularly rich in them. The scientists separated different types of saponins and used mass spectrometry to measure their mass and hypothesize how they are constructed. Later, the scientists isolated some of the saponins and studied their structure using nuclear magnetic resonance, and at the same time studied the expression patterns of the genes involved in their production.
The tests revealed that the production of saponins occurs in ten main steps, each of which is controlled by a different enzyme. The scientists named the enzyme family SOAP and numbered them from 1 to 10. They quickly identified nine of the ten, but one enzyme, SOAP5, whose function is to attach a sugar tag called glucuronic acid to the saponin molecule, remained a mystery for a long time. Although this function is usually performed by a specific enzyme family, no enzyme from this family carried the burden in spinach.
Prof. Aharoni speculated that the mysterious SOAP5 may be a completely different type of enzyme, and pointed to a possible "suspect" that belongs to a family of enzymes that is usually involved in cell production and is usually found in the cell wall, and not in the intraplasmic reticulum - the organelle where the saponins are formed. This hypothesis turned out to be correct, and the scientists confirmed the surprising finding not only in spinach, but also in several other plants that produce large amounts of saponins, including soy, alfalfa, licorice, beets and quinoa.
"We were very surprised to discover that an enzyme belonging to the 'wrong' family is involved in the production of saponins," says Dr. Jozwiak and illustrates the magnitude of the surprise: "It's like watching a carpenter hammer a nail with a spanner."
Prof. Aharoni speculates that this "unusual" use of the enzyme represents a case of molecular "kidnapping": "Probably during the evolution of plants, this essential enzyme was 'kidnapped' to contribute to the production of substances that protect the plant."
"Our findings may allow for the first time a sustainable industrial production of synthetic saponins - instead of extracting them from plants and depleting natural resources," concludes Dr. Jozwiak. In fact, the institute's scientists have already demonstrated the production of saponins: they inserted all ten genes responsible for production into a tobacco-like plant (Nicotiana benthamiana) and caused it to produce one of the saponins of spinach, and also caused yeast to produce the saponin molecule that is used as a particularly sweet sugar substitute. The research findings may Allow not only to produce saponins - but also to inhibit their production by neutralizing the gene of only one enzyme: SOAP5. Inhibiting the production of saponins may help eliminate the bitter taste that characterizes them - a bitterness that requires washing the plants, as anyone who has cooked quinoa knows.
Dr. Prashant Sunawan, Dr. Shantan Panda and Efrat Almakis Zigel from the Department of Plant and Environmental Sciences participated in the study; Dr. Hassan Masalha from the Department of Molecular Biology of the Cell; Dr. Tali Sharaf from the Department of Chemical Research Infrastructures; Dr. Constantine Garagonis and Prof. Cleopa Papadopoulou from the University of Thessaly in Larisa, Greece; and Dr. Bekala Aviva from the Director of Agricultural Research - Volcanic Center.
