Drought represents a prevalent abiotic stress in terrestrial plants, frequently impairing crop growth and yield. In this paper, we characterized the functional role of OsNAC25, a member of the NAC transcription factor family, in drought tolerance. OsNAC25 was predominantly localized in both the cytoplasm and nucleus, with its expression being markedly induced under drought conditions. Under severe drought stress, the overexpression of OsNAC25 rice exhibited decreased malondialdehyde (MDA) levels, attenuated oxidative damage, and improved survival rate during the vegetative growth stage. The transcriptome analysis revealed that OsNAC25 coordinates drought response through key pathways associated with phenylpropanoid biosynthesis, plant hormone signal transduction, and diterpenoid biosynthesis. Collectively, our findings highlight OsNAC25 as a pivotal transcriptional regulator governing drought resistance in rice. This study not only provides a candidate gene for improving drought tolerance in rice but also offers valuable insights into the molecular mechanisms underlying drought adaptation in cereal crops.

In the context of global climate change, the co-occurrence of salt and heat stress represents a major constraint to rice production, resulting in greater yield penalties than either stress alone. This study aimed to assess the effects of salt and heat stress on oxidative homeostasis, photosynthetic performance, carbon (C)–nitrogen (N) metabolism, and rice yield. The experiment comprised four treatments, i.e., control (CK), salt (irrigation with 3.9 dS m⁻¹ NaCl solution), heat (exposure to 36 °C/30 °C day/night for 5 days at panicle initiation), and combined salt + heat stress. Results showed that combined stress enhanced reactive oxygen species (ROS) accumulation (i.e., H₂O₂ content and O₂⁻ contents were 1.3 and 1.5 times higher than CK), and the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were increased by 64.6%, 69.5%, and 74.8% higher than CK. At the molecular level, salt + heat stress upregulated antioxidant defense-related genes, i.e., OsAPX2, OsSODCC1, and OsAPX1, while significantly downregulated ion homeostasis-related genes, i.e., OsSOSs, OsHKT1;3, OsHKT1;5, and OsNHX4, and photosynthesis-related genes, i.e., Ospsbo, OsRbcS2, and OsRbcS3, compared with CK. Furthermore, salt + heat stress reduced the activities of C-metabolism enzymes (sucrose phosphate synthase, sucrose synthase, and starch synthase) and N-metabolism enzymes (nitrate reductase, glutamine synthetase, and glutamate synthase), leading to 34.3% and 18.6% lower stem-sheath non-structural carbohydrate accumulation in stem sheath and its translocation rate, respectively, while total N accumulation decreased by 42.9%, as compared with CK. Ultimately, these cascading effects inhibited panicle development and reduced yield. The findings provide a theoretical basis for improving rice tolerance to combined abiotic stresses by targeting oxidative stress mitigation, photosynthetic protection, and key stress-responsive gene regulation.

Background: Soil salinity severely restricts rice growth and productivity, particularly at the seedling stage when plants are highly sensitive to ionic and osmotic stress. Results: In this study, we systematically evaluated the phenotypic, physiological, and molecular responses of the hybrid rice cultivar Jingliangyou 3261 under salt stress. Compared with the control cultivars ( Yuxiangyouzhan , Huazhan , and Jingliangyouhuazhan ), Jingliangyou 3261 seedlings exhibited significantly higher survival rates, less leaf chlorosis, and stronger recovery after stress relief. Physiological analyses indicated smaller declines in chlorophyll content, reduced malondialdehyde (MDA) accumulation, and enhanced synthesis of soluble proteins. Moreover, Jingliangyou 3261 maintained superior ion homeostasis by limiting Na⁺ accumulation and sustaining higher K⁺ levels, resulting in a relatively stable Na⁺/K⁺ ratio. Antioxidant capacity was enhanced, as reflected by elevated superoxide dismutase (SOD) and peroxidase (POD) activities together with reduced reactive oxygen species (ROS) accumulation. Molecular analysis showed that under salt stress, osmotic adjustment genes ( OsP5CS1/2 , OsLEA3 ), ion transport genes ( OsHKT , OsNHX , OsHAK , OsKAT , OsSOS1 ), and antioxidant-related genes ( OsCSD , OsCAT , OsAPX ) were significantly up-regulated in Jingliangyou 3261 . Conclusions: These coordinated physiological and molecular responses provide a comprehensive mechanistic basis for the superior salt tolerance of Jingliangyou 3261. Our findings not only deepen the understanding of salt tolerance mechanisms in hybrid rice but also provide valuable genetic resources for salt-tolerant breeding and the utilization of saline–alkali soils.