Rice is a major food crop to approximately half of the human population. Unfortunately, the starchy endosperm, which is the remaining portion of the seed after polishing, contains limited amounts of micronutrients. Here, it is shown that this is particularly the case for thiamin (vitamin B1). Therefore, a tissue-specific metabolic engineering approach was conducted, aimed at enhancing the level of thiamin specifically in the endosperm. To achieve this, three major thiamin biosynthesis genes, THIC, THI1 and TH1, controlled by strong endosperm-specific promoters, were employed to obtain engineered rice lines. The metabolic engineering approaches included ectopic expression of THIC alone, in combination with THI1 (bigenic) or combined with both THI1 and TH1 (trigenic). Determination of thiamin and thiamin biosynthesis intermediates reveals the impact of the engineering approaches on endosperm thiamin biosynthesis. The results show an increase of thiamin in polished rice up to threefold compared to WT, and stable upon cooking. These findings confirm the potential of metabolic engineering to enhance de novo thiamin biosynthesis in rice endosperm tissue and aid in steering future biofortification endeavours.

中文翻译：

---

水稻胚乳代谢工程提高维生素 B1 积累

水稻是大约一半人口的主要粮食作物。不幸的是，淀粉胚乳是种子抛光后的剩余部分，含有有限量的微量营养素。此处表明，硫胺素（维生素 B1）尤其如此。因此，进行了一种组织特异性代谢工程方法，旨在提高胚乳中特定的硫胺素水平。为了实现这一点，采用了由强胚乳特异性启动子控制的三个主要硫胺生物合成基因THIC、THI1和TH1来获得工程水稻品系。代谢工程方法包括单独的THIC异位表达，结合THI1（双基因）或与THI1和TH1（三基因）结合。硫胺素和硫胺素生物合成中间体的测定揭示了工程方法对胚乳硫胺素生物合成的影响。结果表明，与 WT 相比，精米中硫胺素的含量增加了三倍，并且在烹饪时保持稳定。这些发现证实了代谢工程在增强水稻胚乳组织中硫胺素从头生物合成方面的潜力，并有助于指导未来的生物强化工作。