Overexpression of the LmHQT1 gene increases chlorogenic acid production in Lonicera macranthoides Hand-Mazz

Lonicera macranthoides Hand-Mazz contains high levels of chlorogenic acid (CGA). The CGA is synthesized via different biosynthetic pathways in various plant species, and hydroxycinnamoyl-coenzyme A quinate transferases (HQTs) are key enzymes in these routes. In this study, we isolated the LmHQT1 gene, which encodes a protein of 447 amino acid residues with conserved HXXXD and DFGWG motifs. It is very closely homologous to HQT genes in Lonicera japonica (LjHQT), Solanum lycopersicum (SlHQT) and Nicotiana sylvestris (NsHQT). Quantitative reverse-transcription polymerase chain reaction showed that LmHQT1 gene expression decreased following leaf senescence. The CGA contents displayed similar trends, suggesting a potential role of LmHQT1 in CGA biosynthesis. To characterize its function, LmHQT1 overexpressing plants were generated via Agrobacterium transformation methods established previously. Upregulation of LmHQT1 in L. macranthoides was observed to elevate the CGA levels up to 60% in leaves. These findings indicated that LmHQT1was devoted to CGA biosynthesis in L. macranthoides.