Mechanisms of saponin biosynthesis and their impact on secondary metabolites in and nutrient bioavailability from ‘sweet’ vs. ‘bitter’ quinoa seeds

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Quinoa (Chenopodium quinoa Willd.) is a major Andean seed crop that has become a popular food product in Europe. Quinoa has a high potential to improve food security due to its stress-tolerance, genetic diversity, nutritional quality and low production costs. The United Nations declared 2013 the International Year of Quinoa, and the FAO emphasized the nutritional benefits and agricultural adaptability of quinoa.Quinoa seeds contain essential micronutrients, including vitamin E, pro-vitamin A carotenoids, and minerals, but also anti-nutritional saponins. Because of their bitter taste, saponins need to be removed before consumption, which is time- and resource-consuming and adds to the production costs. Breeding efforts therefore focus on producing quinoa accessions with low saponin content (‘sweet’). In floral clusters of ‘sweet’ accessions we observe a transcriptional down-regulation of many genes in the mevalonate (MVA) pathway, which results in saponin biosynthesis. The pathway is also involved in the synthesis of vitamin E, carotenoids, and phytosterols, which raises the question if the downregulation of the MVA pathway in ‘sweet’ quinoa also influences the content of these important and in part essential nutrients in quinoa seeds. Furthermore, if the contents of nutrients and anti-nutritional compounds are both altered, how does this affect their digestion, bioaccessibility and absorption in humans? This project brings together experts in plant science, saponins, and human nutrition to investigate the mechanisms regulating saponin and nutrient synthesis in quinoa and their impact on digestion and bioaccessibility of essential nutrients for humans.