Full-length transcriptome sequencing and transgenic tobacco revealed the key genes in the chlorogenic acid synthesis pathway of Sambucus chinensis L.

Chlorogenic acid is a key chemical in antioxidation and antisepsis. Sambucus chinensis L. is an herbaceous plant rich in chlorogenic acid and a potential genetic resource for breeding high-chlorogenic acid plants. However, there are few studies on the synthesis pathway of chlorogenic acid in S. chinensis. Our study found chlorogenic acid accumulation in S. chinensis to be organ-specific, higher in leaves and buds but lower in roots, stems and fruits. A total number of 546,844 CCS (circular consensus sequence), including 402,767 full-length nonchimeric (FLNC) and 39 annotated sequences related to the synthesis of chlorogenic acid, was obtained by single-molecule real-time sequencing technology (SMRT). qRT-PCR showed that a number of key genes involved in chlorogenic acid synthesis were differentially expressed in various tissues of S. chinensis. Transgenic tobacco revealed that ectopic expression of the HCT homologous gene HCT-45178 increased the content of chlorogenic acid. Our results should be the first report of full-length transcriptome data of S. chinensis, which help to understand the basis of chlorogenic acid synthesis and provide a novel strategy for breeding tobacco cultivars with higher levels of chlorogenic acid.