Enhanced carbon backbone supply via the mevalonate pathway confers sesquiterpene accumulation in Atractylodes macrocephala rhizomes under low temperature

Although moderate temperature stress can enrich specific ingredients in medicinal plants, its effect on the secondary metabolism of Atractylodes macrocephala Koidz. (A. macrocephala) remains unknown. Two-month-old A. macrocephala plants derived from one-year-old rhizomes were grown in pots and exposed to day/night temperatures of 8/0°C, 16/8°C, or 40/32°C, with 28/20°C as the control. Following 8 and 12 days’ treatment, 8/0°C increased the content of atractylone, a major sesquiterpene that could be further converted to atractylolides, in rhizomes by 51.0 % and 44.8 %, respectively, exceeding the decline in rhizome biomass. This finding indicates that such enrichment resulted from biosynthetic induction rather than concentration effects due to growth inhibition. Increased activity of major enzymes responsible for sucrose hydrolysis, glycolysis, and the citrate cycle at 8/0°C indicated improved primary carbon metabolism, providing adequate acetyl-CoA pools for terpenoid backbone synthesis. Transcriptomic analysis showed that 8/0°C upregulated hydroxymethylglutaryl-CoA reductase (HMGR) genes while downregulating methylerthritol-4-phosphate pathway genes, facilitating carbon flux to the mevalonate pathway. Furthermore, 8/0°C elevated farnesyl diphosphate synthase gene expression but reduced geranylgeranyl pyrophosphate synthase gene expression enabled precursors to be allocated to sesquiterpene production. Therefore, 8/0°C promotes atractylone accumulation in A. macrocephala rhizomes by optimizing precursor supply and diverting metabolic flux. This work provides novel insights for improving the medicinal quality of A. macrocephala.