Phycofabricated zinc oxide nanoparticles and hydrogen sulfide confer drought tolerance in rice (Oryza sativa L.) by modulating abscisic acid signaling and redox homeostasis

Abstract

Global food security is increasingly challenged by drought stress (DS), a threat intensified by climate change. Developing sustainable, chemistry-driven strategies to enhance crop resilience is therefore critical. Here, we demonstrate that rice (Oryza sativa L. cv. Swarna Sub1) exposed to 12% polyethylene glycol-induced DS exhibited markedly improved tolerance after priming with phycofabricated zinc oxide nanoparticles (ZnO-NPs), in combination with sodium hydrosulfide (NaHS), a hydrogen sulfide donor. The food-compatible ZnO-NPs enabled sustained release and targeted delivery, while NaHS amplified stress-responsive signaling. This dual treatment enhanced abscisic acid (ABA) biosynthesis (upregulation of OsNCED5, OsZEP), activated sulfur-assimilation pathways, and strengthened antioxidant defenses, thereby maintaining redox balance, limiting ROS accumulation, and stabilizing H⁺-ATPase activity. Physiological benefits included improved carbonic anhydrase activity, chlorophyll fluorescence, and leaf thermal regulation, together with reduced root tissue distortion and dehydration. Mitochondrial integrity and genomic stability were preserved under DS. These findings reveal a novel, green nanomaterial-gasotransmitter synergy that integrates molecular signaling with sustainable nanotechnology to fortify drought resilience in rice, offering a promising route to safeguard food production under water-limited conditions.