Free amino acid production in response to selenium nanoparticles in rice plants

Abstract

Rice (Oryza sativa L.) is the main food source for nearly half of the world's population. Selenium nanoparticles (SeNPs) have emerged as potential agents in plant sciencedue to their ability to mitigate biotic and abiotic stresses, and increase plant productivity. Free amino acids (FAA) are key metabolites involved in plant stress responses and homeostatic regulation. The present study investigated the FAA profiles in response to SeNP treatment which ranged from 0 -to25 ppm in two-week-old rice plants. The concentration of FAA was determined by using high-performance liquid chromatography. Results demonstrated a dose-dependent increase in FAA accumulation, with the highest concentration (25 ppm SeNPs) leading to maximum FAA content in shoots (approximately 33 mg/g dry weight), compared to roots (11–13 mg/g). Moreover, increased concentration of SeNPs stimulated more total FAA production. The aspartate family contributed the largest fraction of total FAA, comprisingapproximately 50% under 25 ppm treatment. Additionally, essential amino acid levels significantly increased with higher SeNP concentrations, reaching approximately 23 mg/g in shoots at 25 ppm. The accumulation of lysine, threonine, and serine was notably enhanced in response to SeNP treatment, suggesting their involvement in protective or compensatory metabolic pathways under stress conditions. Among these, lysine exhibited the highest level of accumulation, indicating a potentially prominent role in the plant's adaptive response to SeNP-induced stress. These findings highlight SeNP-induced modulation of FAA metabolism in rice and suggest a potential mechanism for enhancing stress resilience through targeted amino acid biosynthesis.