Altered Steroidal Glycoalkaloid (SGA) Biosynthesis in Diploid Potatoes as Induced by EMS-Mutagenesis

Abstract

Steroidal glycoalkaloids (SGAs) can be toxic to humans at more than 100 mg/100 g dry weight of potato tubers. The objective of the current study was to characterize phenotypically and genotypically a subset of 1750 ethyl methane sulfonate (EMS)-mutagenized diploid potato clones previously reported in our group for altered SGA production. The study reports on a wide range of SGA profiles in 246 EMS-mutant lines, of which 14% showed lower SGA content than the wild types and commercial varieties. An Ampliseq gene panel sequencing of 9 key SGA biosynthetic genes from 87 EMS-treated lines showing varied SGA profiles revealed 61 unique functional SNP mutations in 56 unique EMS-treated individual lines. Mutational frequencies in the target genes ranged from 1/16 kb (SGT2) to 1/341 kb (GAME7), with an average of 1/47 kb. Among these mutations, mutations were detected in GAME7, GAME6, GAME11, GAME4CH6, GAME4CH12, and SGT3 genes of low SGA EMS-treated lines, genes deemed essential for steroidal aglycone hydroxylation, oxidation, and solanidine glycosylation. Subsequent comparative transcriptomic analysis of a low SGA mutant line and a high SGA wild type line showed significant downregulation of UDP-glycosyltransferases and cytochrome P450s expression in the low SGA EMS-mutant line. Using EMS-mutagenesis, this study is the first to show evidence of an effective alteration of SGA production in diploid potato tubers and paves the way for more functional analysis of this mutant population as well as diploid mutant potato cultivar development.