Multi-omics revealed the mechanisms of AgNP-priming enhanced rice salinity tolerance

Rice is highly susceptible to salt stress. Increasing the salt tolerance of rice is critical to reduce yield loss. Herein, we investigated the possibility of using an AgNP-based priming method (seed soaking (SP) and leaf spraying (LP)) to enhance rice salt tolerance. Under saline conditions, both SP (40 mg L-1) and LP (similar to 0.15 mg per plant) significantly increased the biomass (10.4-13.4%) and height (6.6-6.9%) of 6-week-old rice seedlings. In addition, SP significantly increased chlorophyll a (7.3%) and carotenoid (7.9%) content as well as total antioxidant capacity (10.5%), whereas it decreased malondialdehyde (MDA) content (16.9%) in rice leaves. These findings indicate that AgNP priming, especially SP, improved the salt tolerance of rice seedlings. A life cycle field study conducted in a real saline land revealed that SP significantly increased the rice grain yield by 25.8% compared to hydropriming. Multi-omics analyses demonstrated that AgNP priming induced metabolic and transcriptional reprogramming in both seeds and leaves. Notably, both SP and LP upregulated osmoprotectants in seeds and leaves. Furthermore, several transcriptional factors (TFs), such as WRKY and NAC, and salt-tolerance related genes, including the high-affinity K+ channel gene (OsHKT2;4, OsHAK5), the Ca2+/proton exchanger (CAX4), and the cation/Ca2+ exchanger (CCX4), were upregulated in leaves. Omics data provide a deep insight into the molecular mechanisms for enhanced salinity tolerance. Together, the results of this study suggest that seed priming with AgNPs can enhance the salt tolerance of rice and increase rice yield in saline soil, which provides an efficient and simple way to engineering salt-tolerant rice.