摘要Soyasaponins are major small molecules that ac-cumulate in soybean(Glycine max)seeds.Among them,type-A soyasaponins,fully acetylated at the terminal sugar of their C22 sugar chain,are re-sponsible for the bitter taste of soybean-derived foods.However,the molecular basis for the ace-tylation of type-A soyasaponins remains unclear.Here,we identify and characterize GmSSAcT1,encoding a BADH-type soyasaponin acetyl-transferase that catalyzes three or four consec-utive acetylations on type-A soyasaponins in vitro and in planta.Phylogenetic analysis and bio-chemical assays suggest that GmSSAcT1 likely evolved from acyltransferases present in legumi-nous plants involved in isoflavonoid acylation.Loss-of-function mutants of GmSSAcT1 exhibited impaired seed germination,which attribute to the excessive accumulation of null-acetylated type-A soyasaponins.We conclude that GmSSAcT1 not only functions as a detoxification gene for high accumulation of type-A soyasaponins in soybean seeds but is also a promising target for breeding new soybean varieties with lower bitter soyasa-ponin content.