Fig. 4: Tissue expression profiles of key enzyme genes in the predicted iridoids biosynthetic pathway of R. chingii.

a Phenotype of the selected tissues used for transcriptome analysis. b Total iridoid contents in roots, stems, leaves, and corollas. Values are means ± SD of three biological replicates. c Total iridoid contents in veinless leaves, leaf veins, root cortices, root xylems, and tender shoots. Values are means ± SD of three biological replicates. d Expression patterns of enzyme genes involved in the iridoids biosynthetic pathway, identified via BLAST alignment with C. roseus amino acid sequences. Transcript levels from RNA-seq data are visualized as heatmaps and normalized with log₁₀(FPKM + 1). DXR 1-deoxy-D-xylulose 5-phosphate reductoisomerase, DXS 1-deoxy-D-xylulose-5-phosphate synthase, CMS 2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase, CMK 4-(cytidine 5′-diphospho)-2-C-methyl-D-erythritol kinase, MCS 2-C-methyl-D-erythritol 2,4-cyclodiphosphate synthase, HDS (E)−4-hydroxy-3-methylbut-2-enyl-diphosphate synthase, HDR 4-hydroxy-3-methylbut-2-en-1-yl diphosphate reductase, AACT acetyl-CoA C-acetyltransferase, HMGS hydroxymethylglutaryl-CoA synthase, HMGR hydroxymethylglutaryl-CoA reductase, MVK mevalonate kinase, PMK phosphomevalonate kinase, MVD diphosphomevalonate decarboxylase, IPI isopentenyl-diphosphate Delta-isomerase, GPPS geranyl diphosphate synthase, GES geraniol synthase, G10H geraniol 10-hydroxylase, 10HGO 10-hydroxygeraniol dehydrogenase, IS iridoid synthase, IO iridoid oxidase. In (b, c), Different letters above the bars indicate significant differences (P < 0.05) as determined by one-way ANOVA with Tukey’s tests. Source data are provided as a Source Data file.