De novo transcriptome sequencing of Vaccinium dunalianum Wight to investigate arbutin and 6'-O-caffeoylarbutin synthesis

his study aimed to investigate potential pathways associated with arbutin synthesis and potential synthetic routes to 6′-O-caffeoylarbutin (CA) in Vaccinium dunalianum Wight (Ericaceae) via de novo transcriptome sequencing. De novo transcriptome sequencing of leaf buds of V. dunalianum was performed. After quality control and transcriptome assembly, unigenes were predicted and their functions were annotated using Blast2GO. Furthermore, the coding sequences of unigenes were predicted based on NR, SWISS-PROT, KEGG and COG databases. Subsequently, pathways related to arbutin synthesis and potential synthetic routes to CA were analyzed based on KEGG and ExPASy databases. In total, 55537512 clean reads (11.7 G) were generated, and there were 4998376080 nt clean nucleotides. The majority of unigenes were related to the pathways of metabolism, such as carbohydrate and lipid metabolism. Besides, a set of enzymes were related to uridine diphosphate (UDP)-glucose synthesis (e.g. K01784) via some pathways, such as amino sugar and nucleotide sugar metabolism, starch and sucrose metabolism, etc. Some other enzymes were associated with hydroquinone synthesis (e.g. K15849) via tyrosine metabolism. Additionally, chlorogenic acid, caffeoyl-CoA and 1-O-hydroxycinnamoyl-β-D-glucose (HCA-Glc) were predicted to participate in CA synthesis as acyl donors. Some enzymes in pathways related to glycometabolism (e.g. K01784) and tyrosine metabolism (e.g. K15849) may participate in arbutin synthesis. Additionally, chlorogenic acid, caffeoyl-CoA and HCA-Glc may take part in CA synthesis.