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.