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<p>Lipolysis in germinating seeds accompanies important metabolic signatures associated with lipid mobilization and seedling longevity under challenging environments. The present work provides new information on melatonin as an important regulator of lipolysis in cotyledons of NaCl-stressed sunflower seedlings under light and dark regimes. Four consecutive photoperiodic exposures of fixed light intensity (16&#xa0;h light and 8&#xa0;h dark) were provided to analyze various parameters associated with lipid mobilization, protease activity, H<sub>2</sub>S metabolism and Na<sup>+</sup>/K<sup>+</sup> content in 4 d old seedling cotyledons. Melatonin (MT) treatment in dark-grown seedlings resulted in a reduction in Na<sup>+</sup>/K<sup>+</sup> ratio under NaCl stress. Thin layer chromatographic analysis of neutral lipids revealed differential accumulation of various forms namely- TAG, FFA, 1,2-DAG; 1,3-DAG and MAG in the presence of light and melatonin treatment under NaCl stress. Fluorescent localization of H<sub>2</sub>S distribution revealed its accumulation to be regulated by MT treatment and NaCl stress in both light and dark grown seedlings. We observed interesting correlations among the activity of lipid mobilizing enzymes- fatty acyl-ester hydrolase (lipase), lipoxygenase (LOX), and phospholipase A2 (PLA2). While LOX and PLA2 activity was significantly higher in the light-grown NaCl-stressed seedling cotyledons, MT treatment markedly reduced their activity, thereby suggesting slower lipid mobilization. Subsequent to the activity of lipolytic enzymes, we observed a considerably high total protease activity in the imbibed seeds, which showed a greater prevalence of serine protease. MT treatment, however, led to reduced protease activity and differential regulation of metallo-protease and serine protease in seedlings. Precisely, MT application slows down lipolysis and proteolysis in cotyledons of sunflower seedlings raised in light exposure. Delayed lipolysis in seedlings under MT treatment might act as a regulatory mechanism for sustainable release of lipid reserve, thereby improving seedling longevity under NaCl stress.</p>

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Integrative Impacts of Melatonin and Light Application on Lipolytic Events Accompanying Altered Protease activity, Na+/K+ Homeostasis and Differential accumulation of H2S in NaCl-Stressed Sunflower Seedling Cotyledons

  • 期刊论文

  • 发表日期：

    2026年1月5日

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  • Ganapati Basak,
  • Md Rihan Haque,
  • Chandan Barman,
  • Soumya Mukherjee

摘要

Lipolysis in germinating seeds accompanies important metabolic signatures associated with lipid mobilization and seedling longevity under challenging environments. The present work provides new information on melatonin as an important regulator of lipolysis in cotyledons of NaCl-stressed sunflower seedlings under light and dark regimes. Four consecutive photoperiodic exposures of fixed light intensity (16 h light and 8 h dark) were provided to analyze various parameters associated with lipid mobilization, protease activity, H2S metabolism and Na+/K+ content in 4 d old seedling cotyledons. Melatonin (MT) treatment in dark-grown seedlings resulted in a reduction in Na+/K+ ratio under NaCl stress. Thin layer chromatographic analysis of neutral lipids revealed differential accumulation of various forms namely- TAG, FFA, 1,2-DAG; 1,3-DAG and MAG in the presence of light and melatonin treatment under NaCl stress. Fluorescent localization of H2S distribution revealed its accumulation to be regulated by MT treatment and NaCl stress in both light and dark grown seedlings. We observed interesting correlations among the activity of lipid mobilizing enzymes- fatty acyl-ester hydrolase (lipase), lipoxygenase (LOX), and phospholipase A2 (PLA2). While LOX and PLA2 activity was significantly higher in the light-grown NaCl-stressed seedling cotyledons, MT treatment markedly reduced their activity, thereby suggesting slower lipid mobilization. Subsequent to the activity of lipolytic enzymes, we observed a considerably high total protease activity in the imbibed seeds, which showed a greater prevalence of serine protease. MT treatment, however, led to reduced protease activity and differential regulation of metallo-protease and serine protease in seedlings. Precisely, MT application slows down lipolysis and proteolysis in cotyledons of sunflower seedlings raised in light exposure. Delayed lipolysis in seedlings under MT treatment might act as a regulatory mechanism for sustainable release of lipid reserve, thereby improving seedling longevity under NaCl stress.