Integrated Metabolomic and Transcriptomic Analysis of Volatile Organic Compound Biosynthesis During Mung Bean (Vigna radiata) Seed Development

Mung bean (<i>Vigna radiata</i> L.) is globally cultivated and has been widely used in the food industries. Other than nutrients, the composition of the volatile organic compounds (VOCs) often influences the quality of mung bean-based products. However, the dynamics of VOCs and the flavor changes during mung bean seed development remain unexplored. This study investigated the VOC and flavor composition in four mung bean varieties by integrating relative odor activity value (ROAV) evaluation and transcriptomic analysis. A total of 65 VOCs were identified, with eucalyptol serving as a key maturity indicator in LL655 and SH-1, while nonanal contributed significantly to the characteristic beany flavor across all varieties. Transcriptomic analysis revealed four downregulated geranylgeranyl diphosphate synthase genes during seed development, leading to terpenoid accumulation patterns. Terpenoids, including trans-beta ocimene and gamma-terpinene, appeared to be regulated by transcription factors (TFs) from the RLK-Pelle, WRKY, AP2/ERF, bHLH, and bZIP families. Additionally, two MYB TFs showed potential roles in modulating the accumulation of phenylpropanoid/benzenoid derivatives. This study provides a comprehensive understanding of the VOC accumulation and flavor variation during mung bean seed development, enriches the knowledge of flavor chemistry in mung bean varieties, and facilitates a theoretical foundation for optimizing and developing mung bean-based products.