Abstract
Garden asparagus (Asparagus officinalis L.) is a popular vegetable cultivated worldwide. The secondary metabolites in its shoot are helpful for human health. We analyzed A. officinalis transcriptomes and identified differentially expressed genes (DEGs) involved in the biosynthesis of rutin and protodioscin, which are health-promoting functional compounds, and determined their association with stem color. We sequenced the complete mRNA transcriptome using the Illumina high-throughput sequencing platform in one white, three green, and one purple asparagus cultivars. A gene set was generated by de novo assembly of the transcriptome sequences and annotated using a BLASTx search. To investigate the relationship between the contents of rutin and protodioscin and their gene expression levels, rutin and protodioscin were analyzed using high-performance liquid chromatography. A secondary metabolite analysis using high-performance liquid chromatography showed that the rutin content was higher in green asparagus, while the protodioscin content was higher in white asparagus. We studied the genes associated with the biosynthesis of the rutin and protodioscin. The transcriptomes of the five cultivars generated 336 599 498 high-quality clean reads, which were assembled into 239 873 contigs with an average length of 694 bp, using the Trinity v2.4.0 program. The green and white asparagus cultivars showed 58 932 DEGs. A comparison of rutin and protodioscin biosynthesis genes revealed that 12 of the 57 genes associated with rutin and two of the 50 genes associated with protodioscin showed more than four-fold differences in expression. These DEGs might have caused a variation in the contents of these two metabolites between green and white asparagus. The present study is possibly the first to report transcriptomic gene sets in asparagus. The DEGs putatively involved in rutin and protodioscin biosynthesis might be useful for molecular engineering in asparagus.
Highlights
Asparagus officinalis L. has been used as a medicinal plant and widely consumed globally for a long time, making it is an economically valuable plant [1]
We successfully obtained a complete transcriptome through de novo assembly of the Illumina RNA-seq reads from asparagus spears
We identified seven phenylalanine ammonia-lyase (PAL) genes, which are associated with phenylalanine and initiate flavonoid biosynthesis
Summary
Asparagus was cultured in a farm located in Chuncheon-si, Gangwon-do, Korea. The commonly used cultivars ‘Atlas’ (green and white), ‘Gijnlim’ (green), ‘Pacific purple’ (purple), and ‘UC157’ (green), which were grown for 5 years, were used (Table 1). Asparagus spears (20–25 cm length) were sampled for transcriptome sequencing and metabolite content analysis. The samples were washed with distilled water, immediately frozen in liquid nitrogen, and stored at −80 ̊C for RNA extraction and metabolite content analysis. Asparagus spears of ‘Atlas,’ ‘Gijnlim,’ ‘Pacific purple,’ and ‘UC157’ were frozen in liquid nitrogen and homogenized using a mortar and pestle.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
