TY  - EJOU
AU  - Liu, Tai 
AU  - Xu, Huichun 
AU  - Amanullah, Sikandar 
AU  - Che, Ye 
AU  - Zhang, Ling 
AU  - Jiang, Zeyu 
AU  - Bi, Weiyi 
AU  - Zhu, Lei 
AU  - Wang, Di 

TI  - Melatonin Priming Enhances Potassium Dichromate Stress Tolerance and Morpho-Physiological Performance via Genetic Modulation in Melon (<i>Cucumis melo</i> L.) Plant
T2  - Phyton-International Journal of Experimental Botany

PY  - 2025
VL  - 94
IS  - 12
SN  - 1851-5657

AB  - Heavy metal accumulation in agricultural soil is primarily driven by pesticides, polluted water, and industrial gas emissions, which pose threats to sustainable crop production. Chromium (Cr) stress has an adverse impact on plant development and metabolism, but approaches to reduce its toxicity and enhance plant resistance remain limited. Melatonin is a potent antioxidant involved in regulating various morpho-physiological functions of plants under different abiotic stresses. In this study, we investigated the impact of exogenous melatonin to mitigate the negative effects of potassium dichromate (PD) stress in melon plants and analyzed genetic modulation of morphological, physiological, and biochemical parameters. The obtained results revealed that melatonin treatment (100 µmol L<sup>−1</sup>) considerably improved seed germination rate, promoted plant growth, and stabilized chloroplast ultrastructure of leaves under PD-stress. This physiological resilience was similarly reflected by maintained photosynthetic efficiency and significantly stabilized photochemical parameters (e.g., Fv/Fm and NPQ). At the molecular level, quantitative polymerase chain reaction (qPCR) analysis confirmed that melatonin treatment maintained organelle integrity by upregulating primary metabolism indices and hindering Cr accumulation. Specifically, melatonin reduced the Cr-induced downregulation of chlorophyll biosynthesis genes [<i>CmHEMA</i> (<i>MELO3C006296.2</i>), <i>CmGOGAT</i> (<i>MELO3C008481.2</i>), and <i>CmPOR</i> (<i>MELO3C016714.2</i>)], restoring chlorophyll content by up to 5.08 mg·g<sup>−1</sup>, increased by 67.11%. The expression level of genes [<i>CmSPS</i> (<i>MELO3C003715.2</i>), <i>CmPEPC</i> (<i>MELO3C018724.2</i>), and <i>CmRubisco</i> (<i>MELO3C012180.2</i>)] showed an effective upsurge in carbohydrate synthesis. Moreover, melatonin significantly enhanced the antioxidant system [e.g., increasing SOD (46.13%), POD (35.85%), and APX (25.00%) activities] and promoted the accumulation of lignin and metallothionein [via upregulation of <i>Cm4CL</i> (<i>MELO3C002346.2</i>) and <i>CmMet</i> (<i>MELO3C016513.2</i>) genes], which restricted Cr translocation from the root to the shoot. To summarize, exogenous melatonin application could serve as an effective strategy for mitigating Cr-induced stress in melon by stabilizing basic photosynthetic processes and secondary metabolism through biochemical and molecular defensive mechanisms, thereby preventing Cr translocation by activating the accumulation of secondary metabolites (e.g., lignin and metallothionein) and photo-respiration elements. Our findings provided new perspective to understand melatonin as a viable, multidimensional bio-regulator for improving crop resilience in Cr-polluted agricultural systems.
KW  - <i>Cucumis melo</i>; growth indices; heavy metal; melatonin; stress; toxicity

DO  - 10.32604/phyton.2025.074131