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<p>Salinity stress poses a major constraint to turmeric (<i>Curcuma longa</i> L.) production by reducing curcuminoid yield, a key determinant of its medicinal and commercial value. Although salinity is a well-recognized challenge for crop productivity, the understanding of turmeric’s biochemical and molecular responses under salinity stress is still emerging, providing opportunities to clarify their roles in stress adaptation. This study examined the effects of graded salinity levels (50, 100, and 150 mM NaCl) compared with a 0 mM NaCl control on turmeric, focusing on biochemical changes, antioxidant responses, curcuminoid accumulation, and expression of curcumin biosynthetic genes. Correlations among phenolic content, phenylalanine ammonia-lyase (PAL) activity, total curcuminoids, and gene expression were analyzed to define their contribution to salinity tolerance. Salinity reduced chlorophyll content and increased oxidative damage, along with a marked decline in curcuminoid accumulation. Expression analysis revealed downregulation of <i>diketide-CoA synthase (DCS) and Curcumin synthase 2 (CURS2)</i>, while <i>PAL</i>,<i> Curcumin synthase 1 (CURS1)</i>, and <i>Curcumin synthase 3 (CURS3)</i> were upregulated. PAL enzyme activity and gene expression correlated positively with phenolics but negatively with curcuminoids, indicating a metabolic shift in phenylpropanoid flux. Despite reduced curcuminoids, turmeric accumulated osmolytes and phenolics and enhanced antioxidant enzyme activities, mitigating oxidative stress. Tissue-specific responses showed rhizomes had stronger antioxidant defenses and reactive oxygen species scavenging, whereas leaves were more susceptible to H₂O₂ accumulation and lipid peroxidation, highlighting the rhizome’s protective role. Overall, salinity modulates curcuminoid biosynthesis via gene expression and metabolite allocation, while antioxidant and osmolyte-mediated defenses support stress tolerance, providing insights to optimize curcumin yield under salt stress.</p>

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Integrated biochemical and molecular insights reveal curcuminoid depletion coupled with phenolic–antioxidant elevation in turmeric (Curcuma longa L.) under salinity stress

  • 期刊论文

  • 发表日期：

    2026年1月16日

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  • Madathil Nishma,
  • Mohankumar Saraladevi Resmi,
  • Padmanabhan Jayanthikumari Vivek

摘要

Salinity stress poses a major constraint to turmeric (Curcuma longa L.) production by reducing curcuminoid yield, a key determinant of its medicinal and commercial value. Although salinity is a well-recognized challenge for crop productivity, the understanding of turmeric’s biochemical and molecular responses under salinity stress is still emerging, providing opportunities to clarify their roles in stress adaptation. This study examined the effects of graded salinity levels (50, 100, and 150 mM NaCl) compared with a 0 mM NaCl control on turmeric, focusing on biochemical changes, antioxidant responses, curcuminoid accumulation, and expression of curcumin biosynthetic genes. Correlations among phenolic content, phenylalanine ammonia-lyase (PAL) activity, total curcuminoids, and gene expression were analyzed to define their contribution to salinity tolerance. Salinity reduced chlorophyll content and increased oxidative damage, along with a marked decline in curcuminoid accumulation. Expression analysis revealed downregulation of diketide-CoA synthase (DCS) and Curcumin synthase 2 (CURS2), while PAL, Curcumin synthase 1 (CURS1), and Curcumin synthase 3 (CURS3) were upregulated. PAL enzyme activity and gene expression correlated positively with phenolics but negatively with curcuminoids, indicating a metabolic shift in phenylpropanoid flux. Despite reduced curcuminoids, turmeric accumulated osmolytes and phenolics and enhanced antioxidant enzyme activities, mitigating oxidative stress. Tissue-specific responses showed rhizomes had stronger antioxidant defenses and reactive oxygen species scavenging, whereas leaves were more susceptible to H₂O₂ accumulation and lipid peroxidation, highlighting the rhizome’s protective role. Overall, salinity modulates curcuminoid biosynthesis via gene expression and metabolite allocation, while antioxidant and osmolyte-mediated defenses support stress tolerance, providing insights to optimize curcumin yield under salt stress.