Although abscisic acid (ABA) is an important hormone that regulates seed dormancy, stomatal closure, plant development, as well as responses to environmental stimuli, the physiological mechanisms of ABA response to multiple stress in rice remain poorly understood. In the ABA biosynthetic pathway, 9-cis-epoxycarotenoid dioxygenase (NCED) is the key rate-limiting enzyme. Here, we report important functions of OsNCED3 in multi-abiotic stress tolerance in rice. The OsNCED3 is constitutively expressed in various tissues under normal condition, Its expression is highly induced by NaCl, PEG, and H₂O₂ stress, suggesting the roles for OsNCED3 in response to the multi-abiotic stress tolerance in rice. Compared with wild-type plants, nced3 mutants had earlier seed germination, longer post-germination seedling growth, increased sensitivity to water stress and H₂O₂ stress and increased stomata aperture under water stress and delayed leaf senescence. Further analysis found that nced3 mutants contained lower ABA content compared with wild-type plants, overexpression of OsNCED3 in transgenic plants could enhance water stress tolerance, promote leaf senescence and increase ABA content. We conclude that OsNCED3 mediates seed dormancy, plant growth, abiotic stress tolerance, and leaf senescence by regulating ABA biosynthesis in rice; and may provide a new strategy for improving the quality of crop.

Clade A type 2 C protein phosphatases (PP2CAs) are core regulatory factors in the plant abscisic acid (ABA) signaling pathway. They play crucial roles in response to abiotic stress. However, a comprehensive understanding of the functions of individual members of rice PP2CA gene families remains limited. This study investigates the role of OsPP2C68 in response to abiotic stress. Our findings indicated that the OsPP2C68 is highly expressed in the embryo and endosperm, and is subcellular localized in the nucleus. OsPP2C68 knockout mutants reduced seed germination and root and stem lengths under ABA treatment. The mutants also exhibited higher stomatal closure rates, indicating increased sensitivity to ABA. In addition, the OsPP2C68 knockout mutants exhibited altered synthesis of osmolytes and antioxidant enzymes under drought and high salinity stress, along with the differential expression of genes associated with drought and salt stress responses, enhancing rice tolerance to drought and salt. These results collectively identify OsPP2C68 as a negative regulator in the rice ABA signaling pathway. It is responsive to drought and salt stress, and involved in regulating stomatal movement.

Foxtail millet (Setaria italica L.) is a vital cereal food crop with promising development and utilization potential because of its outstanding ability to resist drought stress. However, the molecular mechanisms underlying its drought stress resistance remain unclear. In this study, we aimed to elucidate the molecular function of a 9-cis-epoxycarotenoid dioxygenase gene, SiNCED1, in the drought stress response of foxtail millet. Expression pattern analysis showed that SiNCED1 expression was significantly induced by abscisic acid (ABA), osmotic stress, and salt stress. Furthermore, ectopic overexpression of SiNCED1 could enhance drought stress resistance by elevating endogenous ABA levels and promoting stomatal closure. Transcript analysis indicated that SiNCED1 modulated ABA-related stress responsive gene expression. In addition, we found that ectopic expression of SiNCED1 delayed seed germination under normal and abiotic stress conditions. Taken together, our results show that SiNCED1 plays a positive role in the drought tolerance and seed dormancy of foxtail millet by modulating ABA biosynthesis. In conclusion, this study revealed that SiNCED1 is an important candidate gene for the improvement of drought stress tolerance in foxtail millet and could be beneficial in the breeding and investigation of drought tolerance in other agronomic crops.

Background: Rice (Oryza sativa L.) is one of the most widely cultivated grain crops in the world that meets the caloric needs of more than half the world’s population. Salt stress seriously affects rice production and threatens food security. Therefore, mining salt tolerance genes in salt-tolerant germplasm and elucidating their molecular mechanisms in rice are necessary for the breeding of salt tolerant cultivars. Results: In this study, a salt stress-responsive jacalin-related lectin (JRL) family gene, OsJRL45, was identified in the salt-tolerant rice variety ‘sea rice 86’ (SR86). OsJRL45 showed high expression level in leaves, and the corresponding protein mainly localized to the endoplasmic reticulum. The knockout mutant and overexpression lines of OsJRL45 revealed that OsJRL45 positively regulates the salt tolerance of rice plants at all growth stages. Compared with the wild type (WT), the OsJRL45 overexpression lines showed greater salt tolerance at the reproductive stage, and significantly higher seed setting rate and 1,000-grain weight. Moreover, OsJRL45 expression significantly improved the salt-resistant ability and yield of a salt-sensitive indica cultivar, L6-23. Furthermore, OsJRL45 enhanced the antioxidant capacity of rice plants and facilitated the maintenance of Na⁺-K⁺ homeostasis under salt stress conditions. Five proteins associated with OsJRL45 were screened by transcriptome and interaction network analysis, of which one, the transmembrane transporter Os10g0210500 affects the salt tolerance of rice by regulating ion transport-, salt stress-, and hormone-responsive proteins. Conclusions: The OsJRL45 gene isolated from SR86 positively regulated the salt tolerance of rice plants at all growth stages, and significantly increased the yield of salt-sensitive rice cultivar under NaCl treatment. OsJRL45 increased the activity of antioxidant enzyme of rice and regulated Na⁺/K⁺ dynamic equilibrium under salinity conditions. Our data suggest that OsJRL45 may improve the salt tolerance of rice by mediating the expression of ion transport-, salt stress response-, and hormone response-related genes.

Rice (Oryza sativa L.) is one of the world’s most vital staple crops, providing food for over 50% of the global population. As a salt-sensitive crop, rice is susceptible to damage from soil-soluble salt stress, which can severely reduce rice yield. Here, we aimed to elucidate the molecular mechanisms underlying salt tolerance in rice. Investigation of MADS-box genes involved in abiotic stress responses in rice led to the identification of OsMADS31. To investigate the role of OsMADS31 in salt stress tolerance, we generated its knockout mutant and overexpression lines in Nipponbare (Nip). Phenotypic analysis of T₂-generation OsMADS31 knockout (osmads31) mutants revealed altered panicle morphology and significant reductions in seed-setting rate, panicle length, grain number per panicle, and 1000-grain weight. Under salt stress, both during seed germination and at the three-leaf stage, osmads31 knockout mutants exhibited markedly inhibited growth, whereas OsMADS31 overexpression (OE) lines maintained normal germination and development. At the three-leaf stage, knockout mutants showed significantly lower survival rates following salt treatment and subsequent recovery. Physiological and biochemical assays demonstrated that, compared with wild-type (WT) plants, osmads31 mutants exhibited substantially decreased catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) activities as well as reduced proline (Pro) content. Conversely, compared with WT plants, 3,3’-diaminobenzidine (DAB) and nitroblue tetrazolium (NBT) staining intensities as well as malondialdehyde (MDA) content were significantly higher in osmads31 mutants and significantly lower in OE lines. Transcriptome analysis of WT and osmads31 mutants under salt stress conditions, followed by Gene Ontology (GO) enrichment of the identified differentially expressed genes (DEGs), revealed the enrichment of genes encoding protein kinases, CATs, and transcription factors. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis identified several key pathways including carbon metabolism, amino acid biosynthesis, metabolic pathways, glycolysis/gluconeogenesis, lipid metabolism, and plant hormone signal transduction. Furthermore, weighted gene co-expression network analysis (WGCNA) of the DEGs demonstrated that OsMADS31 enhances salt tolerance by upregulating antioxidant-related genes, activating antioxidant enzymes, and reducing oxidative damage. Our results conclusively show that OsMADS31 improves salt tolerance in rice.