Abstract

Kernels of Prunus mandshurica (Maxim.) Koehne are rich in amygdalin, a cyanogenic glycoside with medicinal and potential functional food properties. However, the mechanisms underlying its biosynthesis and regulation are not well understood. We investigated the mechanisms in two P. mandshurica clones with different amygdalin levels. Dynamic changes in amygdalin, prunasin, and β-glucosidase activities were quantified at five kernel developmental stages. RNA sequencing was employed to systematically identify the key genes and regulatory network associated with amygdalin accumulation. The amygdalin content in clone 783 and 774 kernels showed an initial increase and subsequent decrease, reaching peaks at stages S4 and S3, respectively. Amygdalin levels were significantly higher in clone 783 than in clone 774 at all stages, except S1. Prunasin accumulated early and decreased thereafter in both clones. β-glucosidase activity increased in later stages, correlating with amygdalin content. Differential expression analysis identified 11 genes related to amygdalin metabolism, and the biosynthesis and degradation pathways of amygdalin in kernels of P. mandshurica were mapped using KEGG pathway analysis. Co-expression network analyses (WGCNA) identified four gene modules correlated with amygdalin and prunasin content. 12 key transcription factors were identified, including bHLH, bZIP, and NAC members. This study provides in-depth insights into the biosynthesis of amygdalin and its transcriptional regulatory network in P. mandshurica kernels, laying the groundwork for functional validation of key genes and the regulation of amygdalin content, with potential applications in improving food safety and developing functional ingredients from apricot kernels.