Variation in Melatonin Contents and Genetic Dissection of Melatonin Biosynthesis in Sesame

In recent years, people have become increasingly interested in bioactive molecules in plants that are beneficial to human health, and melatonin (N-acetyl-5-methoxytryptamine) has attracted research attention due to its excellent performance. In this study, the content of melatonin in oilseeds was investigated. From the results, it was found that sesame is an important natural food source of melatonin intake. Furthermore, the variation in melatonin content was explored in a natural sesame population, and its contents varied from 0.04 to 298.62 ng g(−1). Through a genome-wide association study (GWAS), a candidate gene SiWRKY67 was screened that regulates melatonin content in sesame. The sesame hairy root transformation system was developed and used to verify this gene, and it was found that the overexpression of SiWRKY67 could positively promote the melatonin content in the hairy roots. Our results provide not only a foundation for understanding the genetic structure of melatonin content in sesame seeds but also a reference for the marker-assisted breeding of sesame varieties with high melatonin content.