GmMYB93 increases aroma formation in soybean by inhibiting the expression of a betaine aldehyde dehydrogenase gene

Soybean (Glycine max), an exceptionally nutritious crop rich in high-quality proteins and oils, is extensively used in various food products. Aromatic varieties of soybeans are in particular demand. Characterized by its distinctive popcorn-like aroma, 2-acetyl-1-pyrroline (2-AP) is an important volatile compound present in soybeans and other plants. The enzyme betaine aldehyde dehydrogenase (BADH) is closely associated with 2-AP production. However, the transcriptional regulatory network that governs BADH gene expression in soybean remains undefined. In this study, we determined that the transcript levels of the BADH gene, GmBADH2, vary significantly across different soybean organs and differ markedly from those of GmBADH1. We showed that GmMYB93 is a transcriptional repressor that directly regulates the expression of GmBADH2 by binding to the CAGTTA elements in its promoter. Furthermore, the silencing of GmMYB93 significantly reduced 2-AP accumulation in soybeans. Our findings shed light on the genetic mechanisms underlying soybean aroma formation and lay a foundation for developing novel aromatic soybean varieties.