Figure 4.

Analysis of volatile metabolites in M. suaveolens.a Classification of all volatile metabolites. b Classification of terpenoid compounds in M. suaveolens.c The position of menthol and piperitenone oxide peaks in the total ion flow diagram (TIC diagram) of the QC sample mass spectrum. d The main biosynthetic pathway of monoterpene biosynthesis in Mentha. The dotted line shows the unidentified enzyme. The expression (log₂(FPKM+1)) of each gene is shown as a heatmap in leaves (L); 1, 2, and 3 represent three biological replicates. e Relative proportion of five metabolites in the proposed monoterpene biosynthetic pathway. Abbreviations: FPKM, fragments per kilobase of exon model per million mapped fragments; IPGI, isopulegone isomerase; ISPD, isopiperitenone dehydrogenase; ISPR, isopiperitenone reductase; L3H, limonene-3-hydroxylase; LS, 4-hydroxy-3-methylbut2-en-1-yl diphosphate reductase; M. suaveolens/Msua, Mentha suaveolens; PR, pulegone reductase; Sten, Schizonepeta tenuifolia; TIC, total ion chromatogram; QC, quality control.