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Key message <p><Emphasis Type="BoldItalic">Strigolactones mitigate Cr(VI) toxicity in Capsicum annuum by limiting chromium uptake and reprogramming photosynthesis and redox metabolism, thereby preserving chloroplast function and cellular integrity.</Emphasis></p> Abstract <p>Agricultural&#xa0;soil contamination&#xa0;and its impact on the crops require alternative strategies to reduce associated environmental risks. Strigolactones (SLs) are emerging phytohormones that regulate plant development and stress adaptation; however, their role in hexavalent chromium [Cr(VI)] tolerance remains poorly understood. Here, we investigated the mechanistic basis of SL-mediated mitigation of Cr(VI) toxicity in <i>Capsicum annuum</i> using the synthetic analog <i>rac</i>-GR24. Cr(VI) stress severely impaired photosynthetic performance by disrupting photosystem efficiency, suppressing Calvin–Benson cycle enzyme activities, and reducing ATP and NADPH production, leading to excessive reactive oxygen species accumulation and cellular damage. <i>rac</i>-GR24 markedly decreased Cr uptake and restored photosynthetic carbon metabolism by enhancing the expression of key Calvin cycle enzymes and genes such as <i>RbcS, RbcL, PGK, GAPDH</i>, and <i>PRK</i>. The regulation of fluorescence parameters such as <i>Fv/Fm</i>, Ф<sub>PSII,</sub>&#xa0;and&#xa0;ETR improved PSI and PSII functioning, and rebalanced the adenylate and pyridine nucleotide pools. GR24 reinforced redox homeostasis by activating antioxidant defence, stimulating the ascorbate–glutathione and glyoxalase pathways, resulting in reduced lipid peroxidation and improved cell viability. Ultrastructural observations confirmed improved chloroplast integrity and stomatal behavior under SL treatment. The enhancement of photosynthesis and reduction of stress-related biomarkers are probably the consequences of decreased Cr accumulation in roots and shoots upon <i>rac</i>-GR24 treatment, as indicated by the differential expression of <i>SULTR1.2, SULTR1.3, and SULTR3 genes</i>. These findings demonstrate that GR24 could be highly effective in alleviating Cr-induced toxicity in&#xa0;<i>C. annuum</i>. This protective effect is mediated through the coordinated regulation of photosynthetic carbon metabolism and antioxidant defense system, leading to redox regulation, protection of chloroplasts, and better photosynthetic performance.</p> Graphical abstract <p></p>

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Strigolactone-mediated regulation of chromium uptake, redox homeostasis, and photosynthetic carbon metabolism during Cr (VI) stress tolerance in Capsicum annuum L.

  • 期刊论文

  • 发表日期：

    2026年5月12日

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  • Kaiser Iqbal Wani,
  • Huazheng Shao,
  • Yingsai Li,
  • Muhammad Aamir Manzoor,
  • Huizhen Fu,
  • Xu Lu,
  • Shanhan Cheng,
  • Javaria Tabusam,
  • Tariq Aftab,
  • Zhiwei Wang

摘要

Key message

Strigolactones mitigate Cr(VI) toxicity in Capsicum annuum by limiting chromium uptake and reprogramming photosynthesis and redox metabolism, thereby preserving chloroplast function and cellular integrity.

Abstract

Agricultural soil contamination and its impact on the crops require alternative strategies to reduce associated environmental risks. Strigolactones (SLs) are emerging phytohormones that regulate plant development and stress adaptation; however, their role in hexavalent chromium [Cr(VI)] tolerance remains poorly understood. Here, we investigated the mechanistic basis of SL-mediated mitigation of Cr(VI) toxicity in Capsicum annuum using the synthetic analog rac-GR24. Cr(VI) stress severely impaired photosynthetic performance by disrupting photosystem efficiency, suppressing Calvin–Benson cycle enzyme activities, and reducing ATP and NADPH production, leading to excessive reactive oxygen species accumulation and cellular damage. rac-GR24 markedly decreased Cr uptake and restored photosynthetic carbon metabolism by enhancing the expression of key Calvin cycle enzymes and genes such as RbcS, RbcL, PGK, GAPDH, and PRK. The regulation of fluorescence parameters such as Fv/Fm, ФPSII, and ETR improved PSI and PSII functioning, and rebalanced the adenylate and pyridine nucleotide pools. GR24 reinforced redox homeostasis by activating antioxidant defence, stimulating the ascorbate–glutathione and glyoxalase pathways, resulting in reduced lipid peroxidation and improved cell viability. Ultrastructural observations confirmed improved chloroplast integrity and stomatal behavior under SL treatment. The enhancement of photosynthesis and reduction of stress-related biomarkers are probably the consequences of decreased Cr accumulation in roots and shoots upon rac-GR24 treatment, as indicated by the differential expression of SULTR1.2, SULTR1.3, and SULTR3 genes. These findings demonstrate that GR24 could be highly effective in alleviating Cr-induced toxicity in C. annuum. This protective effect is mediated through the coordinated regulation of photosynthetic carbon metabolism and antioxidant defense system, leading to redox regulation, protection of chloroplasts, and better photosynthetic performance.

Graphical abstract