Developing EMS Flax Mutant Lines with Altered SDG Lignan Glucosides

Health benefits for flax seed and its seed coat-containing secoisolariciresinol (SECO) diglucoside (SDG) lignan are rising. SDG is known to be less bioavailable to human intestinal Caco-2 cells than its aglycone SECO, which along with the monoglucoside SMG, are not found naturally in planta. Recently, UGT74S1 was identified and characterized as SDG glucosylation gene. However, whether UGT74S1 mutants would produce altered SDG profiles in planta was unknown. We developed and characterized a flax EMS mutant population by functional genomics approach. Reverse genetics using UGT74S1 targeted amplicon resequencing of 1996 M2 families identified 94 SNP loci, with 4, 44, 8, and 38 loci in the 5’UTR, exon 1, intron, and exon 2, respectively. The 94 SNP loci covered 138 and 23 SNPs detected as heterozygotes and homozygotes, respectively, for a total of 161 SNP mutations in 138 independent M2 families. Eighteen of the 23 homozygote mutations were in exons. Among those, two were nonsense and thirteen missense, of which two located in the PSGP region of 3 M2 lines. Forward genetics assessing the plant characteristics showed morphological variants, and 69 M2 families carrying UGT74S1 exonic mutations displayed large diversity in SDG profiles, highlighting segregation for the trait. M3 and M4 generations were generated from 30 selected families and genotyped using KASP genotyping assays. Five homozygote M3 lines were identified and of which 2 lines showed null SDG production. The data will be discussed in line with the mutational sensitivity of EMS-induced amino acids towards developing flax lines with highly bioavailable metabolites.