Protein Crop's Potential Unlocked by Deciphering Anti-nutrient Biosynthesis

Faba beans are an excellent source of food protein, but about 4% of the world's population are afflicted by favism, which renders them sensitive to the faba bean anti-nutrients vicine and convicine. Now, an international research team has identified the VC1 gene as responsible for the production of these compounds.

Faba beans have actually been a source of food protein since pre-historic times, but a fraction of the population, mostly from warm southern regions, cannot tolerate them. Pythagoras and his followers avoided them, and Roman priests of Jupiter associated them with death. Today, we know that faba beans produce the anti-nutrients vicine and convicine, which cause a risk for favism - a condition arising from damage to red blood cells - for susceptible individuals.

Among legumes - the pod-producing family of plants to which pea, chickpea and soybean also belong - faba beans have the second-highest yield globally. They also have the highest seed protein content of the starch-containing legumes and out-perform soybean in cool climates. Faba beans are consequently a prime protein source for facilitating a global switch to a plant-based diet, considered necessary for significant reductions in carbon emissions.

The VC1 gene is responsible for vicine-convicine content

However, when people deficient in a specific enzyme eat a large portion of uncooked faba beans, vicine and convicine can induce abnormal breakdown of red blood cells. The resultant hemolytic anemia, known as favism, has inevitably limited the potential use of faba beans. Although there are a number of faba bean varieties with low levels of vicine and convicine, the gene responsible for this trait was previously unknown.

Now, the scientists have identified the gene responsible for vicine-convicine content. What is more, they have identified the specific mutation within this gene that causes the reduction in synthesis. They found that all faba bean varieties with a low vicine-convicine content, descended from a single accession found in a genebank, had two nucleotides - the "letters" that make up DNA - inserted within the VC1 gene. This insertion disrupts the VC1 function and is the only known genetic source of low vicine and convicine content.