Natural Variation in GmTAT1, a Tyrosine Aminotransferase, Controls Seed Vitamin E Content in Soybean.
Tocopherols (vitamin E, VE) are major lipid-soluble antioxidants that determine both the nutritional value and oxidative stability of soybean oil. To elucidate the genetic basis of natural variation in seed VE content, we integrated multienvironment QTL mapping, functional genomics, and population genetic analyses in soybean. A recombinant inbred line population derived from the high-VE cultivar Huachun 2 and the low-VE landrace Wayao revealed a stable major QTL, qVE12, on chromosome 12 that explained 20%-31% of the phenotypic variation in VE content. Within the qVE12 interval, GmTAT1, encoding a tyrosine aminotransferase functioning in the Tyr-HGA branch of tocopherol biosynthesis, was identified as the most likely candidate gene. CRISPR/Cas9 knockout and overexpression demonstrated that GmTAT1 positively regulates seed VE accumulation, and GFP fusion assays localized GmTAT1 to the cytosol. In a soybean diversity panel, three major upstream haplotypes linked to GmTAT1 were identified from publicly available genotype data, and a favorable haplotype carrying a candidate regulatory variant at Chr12:30,821,186 was associated with higher total VE in a subset of 144 accessions phenotyped by HPLC. This favorable haplotype remained at low frequency in the broader population and was located in a genomic region with low diversity and differentiation. These findings identify qVE12/GmTAT1 as a practical target and provide linked regulatory polymorphisms for VE biofortification in soybean.