The fascinating battle between a blueberry and a fungus
Throughout the day we consume large amounts of molecules of plant and animal origin through food. Some have healthy properties and others not so much. Many of them have good organoleptic characteristics (color, taste, texture, aroma ...) and others have an unpleasant sensory profile. However, we tend to forget that these molecules play a fundamental role in their original sources, whether from the plant or animal kingdom. Well, plant biochemists are obsessed in knowing what function many molecules perform in the plants in which they are found. And why do we have that obsession? For two reasons: satisfy the scientist's curiosity and anticipate the possible response of the human organism when we consume these molecules, which is crucial before introducing them into other foods or even drugs. Attentive to the story I am going to tell you today.
Pterostilbene is a molecule belonging to a group of phenolic compounds called stilbenes. It is found in various vegetable sources such as grape leaves, peanuts and in one of my favorite foods, blueberries. Due to its antioxidant, anti-cancer, anti-inflammatory, analgesic or anti-cholesterol properties, pterostilbene has become the object of desire for various sectors, such as the food or pharmaceutical industries, which have seen in this compound a key element for the development of new products with High value added.
But to me, due to my passion for blueberries and my profession as a scientist, there is something about the pterostilbene that intrigued me. What mission does this phenolic compound have in cranberry? We decided to investigate it at the University of Murcia. The answer we find is surprising: Pterostilbeno is a lethal weapon used by blueberries to defend against their enemies. Let's see.
'Botrytis cinerea' is a pathogenic fungus of many plant, animal and bacterial species. Its most common goal is grapes, where it causes two different types of infections. On the one hand, the gray rot, which is the result of an infection of soaked plants or in humid conditions. The second type, noble rot, occurs when some conditions of humidity occur with others of dryness. This is how the characteristic sweet dessert wines or typical raisins are produced.
But as I told you before, 'Botrytis cinerea' not only infects the grapes, but also other plant sources, as is the case with my dear blueberries. However, blueberries are very clever and do not sit idly by the fungus offensive. Feeling attacked by 'Botrytis cinerea', blueberries defend themselves by synthesizing a series of compounds called phytoalexins that constitute their first line of defense.
And do you know which is one of the most effective blueberry phytoalexins? Precisely the pterostilbeno that I talked about previously, since this compound has a high antifungal ability. When the cranberry perceives that it is being infected by the fungus, it strikes back by raising its concentrations of pterostilbene and thus aims to defeat its great enemy, 'Botrytis cinerea'.
However, mushrooms are not dumb. Knowing that blueberries have this defense system, they keep an ace up their sleeve. To defend against the action of pterostilbeno, 'Botrytis cinerea' launches a second offensive on this vegetable. What a battle! What weapon does 'Botrytis cinerea' have to attack my beloved blueberries again? A powerful system consisting of two enzymes with great destructive power in the plant kingdom: lacasa and peroxidase.
Death
In the first instance, 'Botrytis cinerea' tries to destroy the pterostilbeno (the blueberry's defensive weapon) by means of the enzyme lacasa ... but it fails. The phenolic structure of pterostilbene is not susceptible to being destroyed by lacasa. But 'Botrytis cinerea' has a second alternative that is effective. I refer to peroxidase, an enzyme of great biochemical interest belonging to the group of oxidoreductases. In a devastating attack the 'Botrytis cinerea' peroxidase enzyme destroys pterostilbene, the main blueberry defense tool. As a result of this attack, three new products are generated that not only do not harm the fungus, but can destroy the cranberry itself. Why? Because these three compounds, highly toxic to the plant but not to the fungus, are very insoluble and unable to eliminate cranberries cause death.
The fungus seemed to have won the battle thanks to its peroxidase activity on the pterostilbene ... but it was not so. The blueberry had a final final surprise prepared for 'Botrytis cinerea'.
The only valid strategy that the plant had left to escape from the enclosure prepared by the fungus was to find a way to quickly get rid of the dangerous oxidation products of pterostilbeno generated by the peroxidase enzyme of 'Botrytis cinerea' ... and found it thanks to molecular encapsulation Several authors have described the amylose / amylopectin system of many species of the plant kingdom as an 'in vivo' model of molecular encapsulation thanks to which plants can trap different molecules inside, causing, among other things, an increase in their solubility.
Well, using molecular encapsulation the cranberry is able to encapsulate the three toxic compounds generated by the fungus peroxidase enzyme. Thus he manages to increase their solubility and eliminate them from their structure, saving their life at the last moment. We can already rest. After an intense biochemical battle, the fungi were defeated and my dear blueberries survived.
Fascinating
Dear readers, nature offers amazing shows. Some of us can observe them with the naked eye and others know thanks to scientific advances. What I have told you today has been a wonderful example that I summarize below. We have a plant (blueberry) and a fungus ('Botrytis cinérea') that has decided to infect it. To defend itself, the blueberry produces a molecule, the pterostilbene, with the ability to annihilate the fungus. However, this repels the counterattack of the plant by launching its second offensive, based on an enzyme, which puts blueberries against the ropes. Ultimately, the blueberry escapes using a molecular encapsulation strategy that helps you save your life. Is nature fascinating or not?
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