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<p>3-Hydroxy-3-methylglutaryl-CoA synthase (HMGS) catalyzes an early step in the mevalonate (MVA) pathway, but its role in trans-polyisoprene (TPI) biosynthesis in <i>Eucommia ulmoides</i> remains unclear. Here, <i>EuHMGS2</i> was isolated from <i>E. ulmoides</i> and functionally characterized by stable overexpression in both <i>Nicotiana benthamiana</i> and <i>E. ulmoides</i>, combined with transcriptomic and metabolite analyses. In 35S::<i>EuHMGS2</i> transgenic <i>N. benthamiana</i> lines, <i>EuHMGS2</i> overexpression caused moderate induction of <i>NbHMGR</i> and <i>NbISPS.</i> Transcriptome analysis further revealed preferential upregulation of competing sterol- and brassinosteroid-related genes, including <i>CYP92A6</i>, <i>DWF4</i>, and <i>DHCR24</i>, whereas terminal triterpenoid synthase genes were not induced. Consistent with these transcriptional changes, sterol content increased, whereas total triterpenoids showed a slight decrease. By contrast, in 35S::<i>EuHMGS2</i> transgenic <i>E.ulmoides</i> lines, <i>EuHMGS2</i> overexpression coordinately upregulated key MVA pathway genes, including <i>EuACAT</i>, <i>EuHMGR</i>, and <i>EuFPS</i>, suggesting enhanced capacity for farnesyl diphosphate biosynthesis. In parallel, <i>EuSQLE</i> and <i>EuLUP2</i> were significantly induced, consistent with increased metabolic flux toward sterol and triterpenoid biosynthesis. Accordingly, total sterol and triterpenoid contents were both significantly elevated, and transmission electron microscopy revealed an increased number of rubber particles. These results demonstrate that <i>EuHMGS2</i> drives distinct transcriptomic and metabolic reprogramming depending on the host species. In <i>E. ulmoides</i>, its overexpression enhances MVA-derived terpenoid accumulation and rubber particle formation through coordinated activation of upstream and downstream pathways, establishing <i>EuHMGS2</i> as a promising target for metabolic engineering.</p>

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Integrative transcriptomic analysis reveals differential regulation of terpenoid biosynthesis by EuHMGS2 overexpression in Nicotiana benthamiana and Eucommia ulmoides

  • 期刊论文

  • 发表日期：

    2026年6月25日

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  • Ai Zhang,
  • Xian Gong,
  • Lijun Qin

摘要

3-Hydroxy-3-methylglutaryl-CoA synthase (HMGS) catalyzes an early step in the mevalonate (MVA) pathway, but its role in trans-polyisoprene (TPI) biosynthesis in Eucommia ulmoides remains unclear. Here, EuHMGS2 was isolated from E. ulmoides and functionally characterized by stable overexpression in both Nicotiana benthamiana and E. ulmoides, combined with transcriptomic and metabolite analyses. In 35S::EuHMGS2 transgenic N. benthamiana lines, EuHMGS2 overexpression caused moderate induction of NbHMGR and NbISPS. Transcriptome analysis further revealed preferential upregulation of competing sterol- and brassinosteroid-related genes, including CYP92A6, DWF4, and DHCR24, whereas terminal triterpenoid synthase genes were not induced. Consistent with these transcriptional changes, sterol content increased, whereas total triterpenoids showed a slight decrease. By contrast, in 35S::EuHMGS2 transgenic E.ulmoides lines, EuHMGS2 overexpression coordinately upregulated key MVA pathway genes, including EuACAT, EuHMGR, and EuFPS, suggesting enhanced capacity for farnesyl diphosphate biosynthesis. In parallel, EuSQLE and EuLUP2 were significantly induced, consistent with increased metabolic flux toward sterol and triterpenoid biosynthesis. Accordingly, total sterol and triterpenoid contents were both significantly elevated, and transmission electron microscopy revealed an increased number of rubber particles. These results demonstrate that EuHMGS2 drives distinct transcriptomic and metabolic reprogramming depending on the host species. In E. ulmoides, its overexpression enhances MVA-derived terpenoid accumulation and rubber particle formation through coordinated activation of upstream and downstream pathways, establishing EuHMGS2 as a promising target for metabolic engineering.