Analysis of Genotypic Variations in the Anthocyanin Biosynthetic Pathway in Potatoes

Anthocyanins are pigments that contribute to plant defense and adaptation to environmental stresses. Given their antioxidant properties and positive impacts on human health, enhancing anthocyanin biosynthesis in plants holds significant economic importance. In potato, several genotypes produce a high amount of anthocyanins, but the molecular mechanisms underlying the genotypic variation of anthocyanin content remain poorly understood. Here, key genes that may determine the genotype-dependent capacity for anthocyanin biosynthesis were analyzed. Anthocyanin content in tubers from five genotypes was measured, and Heimeiren and Desiree, exhibiting high and low anthocyanin content, respectively, were selected. We were unable to identify any evidence of differing activity in anthocyanin biosynthesis enzymes based on single amino acid polymorphism analysis between the two genotypes. However, transcriptome sequencing coupled with prediction of gene function identified 27 candidate genes showing different expression levels in tubers of these genotypes. We additionally verified expression patterns of these genes and found that four genes encoding flavanone 3-hydroxylase, flavonoid 3',5'-hydroxylase, anthocyanin synthase (ANS), and anthocyanin O-methyltransferase (AOMT) were strong candidates for high accumulation of anthocyanins in Heimeiren. Particularly, ANS and AOMT are strong candidates increasing anthocyanin content in the tuber flesh. These results imply that genotype-dependent variations of anthocyanin biosynthesis may be due to difference of gene expression, but not enzymatic activities. Our study suggests key anthocyanin biosynthesis genes showing different expression levels in high- and low-anthocyanin genotypes, offering potential for the metabolic engineering of potatoes to increase anthocyanin content.