Telomere-to-telomere genome assembly and multiomics analyses illustrate the high accumulation of quercetin glucosides in tetraploid <i>Descurainia sophia</i>

Quercetin glucosides are important phytopharmaceutical metabolites in <i>Descurainia sophia</i> seeds, which are widely used in traditional herbal medicine. However, the key genes involved in quercetin glucoside biosynthesis in <i>D. sophia</i> have not been characterized. Herein, we present the telomere-to-telomere genomes of a tetraploid <i>D. sophia</i>, which accumulates high levels of quercetin glucoside, and a diploid <i>D. sophia</i>, which accumulates only trace amounts. Multiomics analyses and uridine diphosphate glucosyltransferase (UGT) enzyme assays revealed that the gene duplication and functional evolution of <i>Dscd6AG01520</i>, an UGT gene, led to high quercetin-3-<i>O</i>-β-d-glucoside and quercetin-3,7-<i>O</i>-β-d-diglucoside accumulation in tetraploid <i>D. sophia</i> seeds. Further UGT enzyme assays with the point mutations of Dscd6AG01520 showed that S213 was a critical amino acid for the enzymatic activity of Dscd6AG01520. In addition, we found that diploid <i>D. sophia</i> evolved from an ancestral crucifer karyotype through chromosome fusion and rearrangement. Collectively, our findings illuminate the mechanism of high quercetin glucoside accumulation in tetraploid <i>D. sophia</i>, clarify the origin of the diploid <i>D. sophia</i> genome, and provide valuable genomic resources for comparative genomics and research into polyploid evolution.