ABSTRACT
In Pogostemon cablin (Blanco) Benth. essential oil, patchoulol and pogostone are the two major bioactive phytochemicals while their in vivo biosynthesis remains largely unknown. In this study, seven genes of the plastidic methylerythritol 4-phosphate pathway (MEP) and three genes of the cytoplasmic mevalonate pathway (MVA) in two cultivars, HN and YN, were isolated. Gene expression and phytochemical profiles across leaves and stems at different developmental stages of the two cultivars were evaluated using quantitative reverse-transcription polymerase chain reaction and gas chromatography-mass spectrometry, respectively. Hierarchical analysis showed that the expression of MVA- and MEP-related genes was clustered similarly in the two cultivars. Phytochemical assay revealed that the contents of patchoulol in leaves and pogostone in stems were regulated in an aging-dependent manner. Pogostone was only detected in stems but not in leaves of the two cultivars. The Pearson correlation analysis suggested that several genes were presumably involved in the biosynthesis of patchoulol and pogostone. In the YN cultivar, the 1-deoxy-d-xylulose-5-phosphate reductoisomerase and isopentenyl pyrophosphate isomerase 2 genes, and 2-C-methyl-d-erythritol 4-phosphate cytidylyltransferase were positively responsible for patchoulol and pogostone biosynthesis, respectively. In the HN cultivar, 3-hydroxy-3-methylglutaryl-coenzyme A reductase and mevalonate diphosphate decarboxylase, and mevalonate kinase expression were positively associated with pogostone and patchoulol biosynthesis, respectively. The genes identified in this study are good candidates for the enhancement of patchoulol content in the leaves or pogostone content in the stems of P. cablin. Taken together, our results lay a solid foundation for better understanding of the mechanism underlying patchoulol and pogostone biosynthesis, which in turn may help to improve their content in P. cablin.
