Integrated metabolome and transcriptome profiling reveals the dynamic molecular control of chlorogenic acid and saponin biosynthesis in developing flowers of Lonicera macranthoides Hand.-Mazz

Lonicera macranthoides is an important traditional Chinese medicinal plant, primarily enriched in chlorogenic acid (CGA) and hederagenin-based saponins. Among its different tissues, the blooming flowers are the main medicinal part harvested. However, the mechanisms regulating CGA and saponin biosynthesis in developing flowers remain poorly understood. Therefore, this study characterized the dynamic changes in CGA and saponin levels in developing flowers at five stages (P1, green bud period; P2, the second white period; P3, the baby fat period; P4, the silver flower period; and P5, the golden flower period) and delved into the underlying regulatory mechanisms through combined metabolome and transcriptome profiling. CGA and saponin biosynthesis in developing flowers are co-regulated, with the highest levels of CGA, macranthoidin B, and total saponins found at P2. Important dynamic metabolic remodeling and transcriptional adjustments occurred during flower transitions, with the numbers of differentially accumulated metabolites and differentially expressed genes increasing with maturation. Plant hormone signal transduction plays crucial roles in regulating metabolic processes in developing flowers. Phenylpropanoid biosynthesis is mainly regulated between P1 and P3. We identified six major candidate regulatory genes for CGA and saponins, including protein NRT1 PTR FAMILY ( LguiA_016350 ), alcohol dehydrogenase ( LguiA_005405 ), thioredoxin ( LguiA_003620 ), choline transporter-like ( LguiA_023132 ), and two proteins of unknown function ( LguiA_031382 and LguiA_009216 ). These genes exhibited decreasing expression from P3, with LguiA_031382 , LguiA_023132 , and LguiA_009216 showing strong significant correlations with 3-hydroxy-3-methylglutaryl-coenzyme A synthase (HMGS), caffeoyl-CoA O-methyltransferase (CCoAMT), and 20 signaling components. Our findings advance the understanding of the molecular network regulating CGA and saponin biosynthesis in L. macranthoides . The high accumulation of CGA, macranthoidin B, and total saponins at P2 suggests that this developmental stage may represent a suitable harvest stage for medicinal purposes. Not applicable