Correlation analysis of chlorogenic acid and luteoloside biosyntheses with transcription levels of HQTs and FNSs in Lonicera species

Organic acids and flavonoids are the main active components in Lonicera species. Chlorogenic acid and luteoloside are important components, and their synthesis is regulated in plants by the phenyl-propanoid synthesis pathway. Downstream of the phenylpropanoid synthesis pathway, hydroxycinnamoyl CoA quinate hydroxycin-namoyl transferase (HQT) and flavone synthase (FNS) are critical enzymes that are involved in chlorogenic acid and luteoloside bio-synthesis, respectively. In this study, we first determined the dynamic accumulations of chlo-rogenic acid, luteoloside and other active components in different growth stages of the flower buds of Lonicera fulvotomentosa through HPLC-DAD and then investigated the expressions of the LJHQT and LJFNS gene families by q-RT-PCR. In addition, we also compared the expression levels of HQT and FNS orthologous genes in vari-ous tissues of Lonicera japonica, L. fulvotomentosa, and Lonicera hypoglauca. The results indicated that the chlorogenic acid contents exhibit leaf accumulation that is preferential in L. fulvotomentosa but exhibit bud accumulation that is preferential in L. japonica and L. hypoglauca. The luteoloside contents show preferential leaf accumulation in these three species. Our results suggest that the leaves and buds of these three species are rich in medicinal ingredients, including chlorogenic acid (CGA) and luteoloside, and therefore can be used as a material to extract CGA and luteoloside rather than being wasted. Furthermore, combined with the transcript expression levels of HQTs and FNSs, we explained the species-specific and tissue-specific occurrence of CGA and luteoloside. We analyzed dynamic changes of components and gene expression and demonstrated that the expressions of HQTs and FNSs in these three species are closely related to the synthesis of chlorogenic acid and luteoloside.