Pruning induced yield and quality variations and the correlated gene expression and phytohormone changes in Lonicera japonica

Abstract

Lonicera japonica Thunb. is widely used in China to make teas, aromatic oils or medicines. The demand for L. japonica is large in China. Pruning measures are used to increase the yield of L. japonica in practice. However, there remains a question whether the quality of L. japonica is increased as well. Our study focused on the accumulations of the primary bioactive components and their molecular mechanisms, as well as the roles of endogenous plant hormones on L. japonica after pruning. To achieve this aim, the flower buds of L. japonica were randomly collected and divided into four groups for agronomic traits investigation, bioactive compound changes detection by liquid chromatography coupled with tandem mass spectrometry (LCMS/MS), the related gene expression levels quantification by quantitative real-time reverse transcription-PCR (qRT-PCR), and endogenous phytohormone changes determination by indirect enzyme-linked immunosorbent assay (ELISA), respectively. Results showed that pruning produced superior flower bud yield but inferior quality in L. japonica, especially at the first harvest time. More specifically, pruning significantly increased the yield (1.4-fold) but significantly decreased contents of chlorogenic acid (1.5-fold), isochlorogenic acid A (1.3-fold), luteoloside (1.4-fold), and isoquercetrin (1.3-fold) at the first harvest time. The decreased hydroxycinnamoyl-CoA quinate hydroxycinnamoyl transferase (HQT) and chalcone isomerase (CHI) gene expression levels were probably the main reasons for L. japonica quality decrease. Pruning also induced flexible phytohormone changes in L. japonica. Indole-3-acetic acid (IAA), cytokines (CKs), jasmonic acid (JA), and abscisic acid (ABA) were the main hormones involving in building shoot architecture, flower development, and plant secondary metabolism. In conclusion, we think the pruning technique should be used carefully or with other agronomic practices to obtain the well balance between yield and quality in L. japonica.