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

藜（Chenopodium quinoa Willd.）是安第斯山脉的一种主要种子作物，已成为欧洲受欢迎的食品。藜麦因其抗逆性、遗传多样性、营养品质和低生产成本，在改善粮食安全方面具有很大潜力。联合国宣布2013年为国际藜麦年，粮农组织强调藜麦的营养价值和农业适应性。藜麦种子含有必需的微量营养素，包括维生素E、维生素A原类胡萝卜素和矿物质，但也含有抗营养的皂苷。由于它们的苦味，皂苷需要在食用前去除，这是耗时和资源消耗的，并且增加了生产成本。因此，育种工作集中于生产具有低皂苷含量（“甜”）的藜麦种质。在“甜”品种的花簇中，我们观察到甲羟戊酸（MVA）途径中许多基因的转录下调，这导致皂苷生物合成。该途径还参与维生素E、类胡萝卜素和植物甾醇的合成，这就提出了一个问题，即“甜”藜麦中MVA途径的下调是否也影响藜麦种子中这些重要且部分必需营养素的含量。此外，如果营养素和抗营养化合物的含量都发生了变化，这将如何影响它们在人体内的消化、生物可及性和吸收？该项目汇集了植物科学，皂苷和人类营养学的专家，以研究藜麦中皂苷和营养素合成的调节机制及其对人类必需营养素的消化和生物可及性的影响。

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.