Decoding anthocyanin biosynthesis regulation in Asparagus officinalis peel coloration: Insights from integrated metabolomic and transcriptomic analyses.

Asparagus is a key global vegetable crop with significant economic importance. Purple asparagus, rich in anthocyanins, stands out for its nutritional value. Despite its prominence, the molecular mechanisms driving purple peel coloration in asparagus remain unclear. This study focuses on three asparagus varieties with distinct peel colors to analyze anthocyanins in both the metabolome and transcriptome, unraveling the regulatory mechanisms. Our findings identify 30 anthocyanins, categorized into five major anthocyanin aglycones across diverse asparagus peel colors. Notably, among the 30 differentially expressed metabolites (DEMs), 18 anthocyanins displayed significantly up-regulated expression in the 'Purple Passion' variety. Key contributors include Cyanidin-3-O-rutinoside-5-O-glucoside and Cyanidin-3-O-sophoroside. Cyanidin-3-O-glucoside is most abundant in 'Purple Passion', while Petunidin-glucoside-galactoside is the least. Analysis of differentially expressed genes (DEGs) displayed 21 structural genes in anthocyanin synthesis, with F3H, DFR, ANS, and one of three UFGTs showing significantly higher expression in the 'Purple Passion' compared to 'Grande' and 'Erasmus'. Additionally, transcription factors (TFs), including 38 MYB, 33 bHLH, and 13 bZIP, also display differential expression in this variety. Validation through real-time qPCR supports the idea that increased expression of anthocyanin structural genes contribute to anthocyanin accumulation. Transient overexpression of AoMYB17 in tobacco further showed that it had the vital function of increasing anthocyanin content. This study sheds light on the mechanisms behind anthocyanin coloration in three distinct asparagus peels. Therefore, it lays the foundation for potential genetic enhancements, aiming to develop new purple-fleshed asparagus germplasms with heightened anthocyanin content.