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<p>The signalling behaviour of melatonin (0.8 µM MT) and nitric oxide (10 µM SNP, NO donor) in response to chromium (120 µM Cr) stress has been explored in two cyanobacteria <i>Nostoc muscorum</i> ATCC 27,893 and <i>Anabaena</i> sp. PCC 7120. The Cr stress caused profound negative effects on growth, exopolysaccharide production, pigments, O<sub>2</sub> yield, and PS II photochemistry in the tested strains. Under excessive Cr accumulation accelerated enzymatic antioxidants (SOD, CAT, POD, and GST) could not maintain the oxidative biomarkers SOR, H<sub>2</sub>O<sub>2</sub>, and malondialdehyde equivalents within limits. The PS II photochemistry (F<sub>V</sub>/F<sub>M</sub>, Psi_o, Phi_Eo, PI<sub>ABS</sub> and Fv/Fo, as well as energy fluxes ABS/RC, TRo/RC, ETo/RC, and DIo/RC) and surface morphology (SEM) of cells were considerably disturbed. Exogenously applied MT and NO, alone and together significantly relieved the cyanobacteria from oxidative stress, thereby a considerable improvement in growth, photosynthesis, and exopolysaccharide level was noticed, and the effect was more pronounced under combined treatment. Furthermore, this effect could occur due to MT and NO-mediated strengthening of enzymatic antioxidants resulting in lowering of oxidative biomarkers, as well as significant decrease in Cr accumulation. The SEM study illustrated Cr-induced deformation on the surface morphology of both cyanobacterial cells which was significantly recovered under the influence of MT and NO. The application of NO scavenger (PTIO) and its biosynthetic inhibitor (L-NAME) demonstrated that NO is an essential acquisition for the functioning of MT in regulating Cr toxicity in test cyanobacteria. In conclusion, the current findings suggest that MT and NO work in collaboration to enhance the survival of biofertilizer <i>Nostoc muscorum</i> ATCC 27,893 and <i>Anabaena</i> sp. PCC 7120 even in Cr contaminated crop fields, hence supporting the goals of sustainable agriculture.</p>

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Nitric oxide involved in melatonin-mediated amelioration of chromium toxicity on growth, PS II photochemistry and oxidative stress in Nostoc muscorum ATCC 27,893 and Anabaena sp. PCC 7120

  • 期刊论文

  • 发表日期：

    2025年11月4日

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  • Shravan Kumar,
  • Renuka Maurya,
  • Kewat Sanjay Kumar,
  • Sheo Mohan Prasad

摘要

The signalling behaviour of melatonin (0.8 µM MT) and nitric oxide (10 µM SNP, NO donor) in response to chromium (120 µM Cr) stress has been explored in two cyanobacteria Nostoc muscorum ATCC 27,893 and Anabaena sp. PCC 7120. The Cr stress caused profound negative effects on growth, exopolysaccharide production, pigments, O2 yield, and PS II photochemistry in the tested strains. Under excessive Cr accumulation accelerated enzymatic antioxidants (SOD, CAT, POD, and GST) could not maintain the oxidative biomarkers SOR, H2O2, and malondialdehyde equivalents within limits. The PS II photochemistry (FV/FM, Psi_o, Phi_Eo, PIABS and Fv/Fo, as well as energy fluxes ABS/RC, TRo/RC, ETo/RC, and DIo/RC) and surface morphology (SEM) of cells were considerably disturbed. Exogenously applied MT and NO, alone and together significantly relieved the cyanobacteria from oxidative stress, thereby a considerable improvement in growth, photosynthesis, and exopolysaccharide level was noticed, and the effect was more pronounced under combined treatment. Furthermore, this effect could occur due to MT and NO-mediated strengthening of enzymatic antioxidants resulting in lowering of oxidative biomarkers, as well as significant decrease in Cr accumulation. The SEM study illustrated Cr-induced deformation on the surface morphology of both cyanobacterial cells which was significantly recovered under the influence of MT and NO. The application of NO scavenger (PTIO) and its biosynthetic inhibitor (L-NAME) demonstrated that NO is an essential acquisition for the functioning of MT in regulating Cr toxicity in test cyanobacteria. In conclusion, the current findings suggest that MT and NO work in collaboration to enhance the survival of biofertilizer Nostoc muscorum ATCC 27,893 and Anabaena sp. PCC 7120 even in Cr contaminated crop fields, hence supporting the goals of sustainable agriculture.