Exogenous Selenium Enhances Manganese Tolerance in Malus Robusta by Modulating Polyamine and Proline Metabolism

Area of Science:

• Plant Physiology
• Environmental Toxicology
• Biochemistry

Background:

• Excess manganese (Mn) is toxic to plants, limiting agricultural productivity.
• Selenium (Se) is known to mitigate heavy metal stress, but its role in Mn toxicity is understudied.

Purpose of the Study:

• To investigate the effects of exogenous selenium (Se) on manganese (Mn) toxicity in Malus robusta seedlings.
• To elucidate the mechanisms underlying Se-mediated alleviation of Mn stress, focusing on Mn accumulation, physiological responses, and metabolic pathways.

Main Methods:

• Malus robusta seedlings were treated with sodium selenite (0.5 μM) under 0.5 mM Mn toxicity conditions.
• Evaluated Mn accumulation, photosynthetic pigments, chlorophyll fluorescence (Fv/fm, ΦPSII), reactive oxygen species (ROS) production, and antioxidant enzyme activities.
• Analyzed polyamine metabolism (putrescine, spermidine, spermine), proline biosynthesis, and the expression/activity of key genes (ODC, ADC, OAT).

Main Results:

• Selenium significantly reduced Mn accumulation and alleviated Mn toxicity, enhancing root growth and photosynthetic parameters.
• Se treatment maintained antioxidant balance by reducing ROS and activating the antioxidant system.
• Se modulated polyamine metabolism by decreasing putrescine (Put) and increasing the (spermidine + spermine)/Put ratio, correlating with downregulated ODC and ADC. Proline content also decreased due to OAT suppression.

Conclusions:

• Selenium enhances the tolerance of Malus robusta to manganese stress by regulating polyamine and proline metabolism.
• This study reveals a potential mechanism for reducing Mn toxicity in plants through Se application and metabolic pathway modulation.