Ethylene Renders Silver Nanoparticles Stress Tolerance in Rice Seedlings by Regulating Endogenous Nitric Oxide...

Area of Science:

• Environmental Science
• Plant Science
• Toxicology

Background:

• Nanotechnology advancements increase silver nanoparticle (AgNP) environmental presence and plant exposure.
• Understanding plant responses to AgNPs is crucial for mitigating phytotoxicity.
• Ethylene's role in mediating plant stress responses requires further investigation.

Purpose of the Study:

• To investigate ethylene's role in AgNP stress tolerance in rice (Oryza sativa L.).
• To explore the involvement of endogenous nitric oxide (NO) as a signaling molecule in AgNP stress response.
• To elucidate the mechanisms underlying AgNP phytotoxicity and tolerance.

Main Methods:

• Rice seedlings were treated with AgNPs, ethephon (ethylene donor), silicon nanoparticles (SiNPs), and l-NG-nitro arginine methyl ester (l-NAME, NO synthesis inhibitor).
• Plant growth, oxidative stress markers, sulfur assimilation, and glutathione (GSH) biosynthesis were assessed.
• Endogenous NO levels were measured to correlate with stress responses.

Main Results:

• AgNPs alone induced oxidative stress, reduced sulfur assimilation and GSH biosynthesis, and increased NO levels, impairing rice growth.
• Ethephon application reversed AgNP-induced toxicity, suggesting ethylene's protective role.
• SiNPs enhanced AgNP toxicity, but ethephon mitigated these combined effects.
• l-NAME application also reversed SiNP/AgNP toxicity, indicating NO's critical role.

Conclusions:

• Ethylene acts as a regulatory switch for AgNP stress tolerance in rice by modulating endogenous NO levels.
• Low endogenous NO is associated with AgNP stress tolerance, whereas high NO levels contribute to AgNP toxicity.
• AgNP toxicity involves disruptions in sulfur assimilation, GSH biosynthesis, and redox status, modulated by NO.