Abstract
As one of the common abiotic stresses, chilling stress has negative effects on rice growth and development. Minimization of these adverse effects through various ways is vital for the productivity of rice. Nanoparticles (NPs) serve as one of the effective alleviation methods against abiotic stresses. In our research, zinc oxide (ZnO) NPs were utilized as foliar sprays on rice leaves to explore the mechanism underlying the effect of NPs against the negative impact of chilling stress on rice seedlings. We revealed that foliar application of ZnO NPs significantly alleviated chilling stress in hydroponically grown rice seedlings, including improved plant height, root length, and dry biomass. Besides, ZnO NPs also restored chlorophyll accumulation and significantly ameliorated chilling-induced oxidative stress with reduced levels of H2O2, MDA, proline, and increased activities of major antioxidative enzymes, superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). We further found that foliar application of ZnO NPs induced the chilling-induced gene expression of the antioxidative system (OsCu/ZnSOD1, OsCu/ZnSOD2, OsCu/ZnSOD3, OsPRX11, OsPRX65, OsPRX89, OsCATA, and OsCATB) and chilling response transcription factors (OsbZIP52, OsMYB4, OsMYB30, OsNAC5, OsWRKY76, and OsWRKY94) in leaves of chilling-treated seedlings. Taken together, our results suggest that foliar application of ZnO NPs could alleviate chilling stress in rice via the mediation of the antioxidative system and chilling response transcription factors.
Highlights
Rice (Oryza sativa L.), a major crop in the world and the staple food for over half of the world’s population, is mostly a tropical crop, but its distribution extends to temperate and subtropical regions [1,2]
The transmission electron microscopy (TEM) images (Figure 1) revealed that the zinc oxide (ZnO) NPs were spherical with regular diameters of 30 nm
Chilling stress significantly decreased the gene expression of antioxidant enzymes (SOD, CAT, and POD) compared to control (Figure 7 and Figure S1), while the application of different concentrations of ZnO NPs greatly increased the gene expression of superoxide dismutase (SOD), CAT, and POD, in chilling-treated rice plants compared to only chilling stress (Figure 7 and Figure S1). These results indicated that ZnO NPs application could relieve oxidative stress in rice seedlings exposed to chilling stress by reducing reactive oxygen species (ROS) and enhancing the expression of antioxidant enzymes
Summary
Rice (Oryza sativa L.), a major crop in the world and the staple food for over half of the world’s population, is mostly a tropical crop, but its distribution extends to temperate and subtropical regions [1,2]. Rice usually encounters environmental stresses such as extreme temperatures, drought, flooding, and high salinity [3], which greatly influence the growth and development of rice. The effects of chilling stress on rice growth and development involve different physiological pathways: affecting photosynthesis through the inhibition of chloroplast formation and chlorophyll biosynthesis in rice leaves [10]; inducing the accumulation of signal substances, e.g., malondialdehyde (MDA) and reactive oxygen species (ROS) [11,12]; accumulating compatible osmolytes, e.g., free proline [13] and impacting antioxidants, such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) [14,15]
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