Maize (Zea mays L.) is one of the most important food crops. Salt stress can hinder crop growth and development, but the molecular mechanisms underlying maize’s response to salt tolerance remain unclear. In this study, we conducted comparative transcriptome, metabolome, and physiological analyses of a salt-tolerant maize inbred line (J1285) subjected to different NaCl concentrations during the seedling stage. The results demonstrated that, with increasing salt concentration, seedling growth parameters and antioxidant enzyme activities (SOD, POD, CAT) exhibited initially increases before subsequently decreasing, peaking at 50–150 mmol/L. Transcriptome data analysis revealed that the experimental groups subjected to 50, 100, 150, and 200 mmol/L treatments had 375, 1043, 2504, and 2328 differentially expressed genes (DEGs) compared to the control group, respectively. Additionally, through GO and KEGG analysis, we found that the DEGs were primarily enriched in the MAPK signaling pathway and plant hormone signal transduction, especially the abscisic acid (ABA) signaling pathway, both of which play instrumental roles in orchestrating the maize response to salt-induced stress. Transcription factors involved in the salt stress response, including WRKY, TIFY, bZIP, and bHLH, were identified. Metabolomic data analysis revealed that the experimental groups subjected to 50, 100, 150 and 200 mmol/L treatments had 44, 335, 278, and 550 differentially expressed metabolites (DEMs) compared to the control group, respectively. The DEMs were mainly enriched in metabolic pathways and the biosynthesis of secondary metabolites. Transcriptomics and metabolomics combined analysis were performed on J1285 seedling leaves, and it was found that the co-enrichment pathways included starch and sucrose metabolism, linoleic acid metabolism, α-linolenic acid metabolism, phenylpropanoid biosynthesis pathway, etc. Collectively, these results will aid in identifying resistance genes and elucidating the molecular mechanisms underlying salt tolerance for maize.

Soil salinization, recognized globally as a significant environmental issue, can directly impact the sustainable development of agriculture worldwide. As a key crop driving the global agricultural economy, maize is particularly vulnerable to the detrimental effects of salt–alkali stress, which can impede its growth and development from germination through the seedling stages. In this study, 32 maize inbred lines were screened for saline–alkali resistance identification. We performed four treatments—200 mmol/L NaCl, 100 mmol/L Na₂CO₃, 200 mmol/L NaCl with 25 mmol/L Na₂CO₃—and distilled water (CK) served as a control with a complete randomized design. Principal component analysis and the membership function value method were employed to evaluate the salt–alkali tolerance of these lines. The results indicate complex correlations among various traits at different growth stages. The relative correlation of each index was established by measuring the key physiological indexes (germination rate, root length and seedling height) of different maize inbred lines at the germination stage and seedling stage and standardizing them via the membership function value method. Subsequently, the principal component analysis method was used to reduce the dimensions of the standardized data, and the main factors affecting maize germination and seedling growth were extracted. The salt–alkali tolerance of maize inbred lines was comprehensively evaluated, and the salt–alkali tolerance and sensitive materials of maize germination and seedling stage were identified. This study found that the coefficient of variation of each trait is relatively rich. Therefore, in the preliminary screening of breeding germplasm resources, different reference indexes can be selected according to different periods and stress conditions. The enzyme activity results revealed significant variations in enzyme activity across different treatments and materials, with changes in superoxide dismutase (SOD) and peroxidase (POD) exhibiting relative stability, thereby reflecting the physiological response mechanisms of maize under salt–alkali stress. In this study, through principal component analysis, it was found that the germ and germination factors at the germination stage of maize and the root weight, root length, and seedling development factors at the seedling stage affected its saline–alkali resistance. The root weight factor, seedling development factor, and root length factor may affect the growth and development of maize at the seedling stage. Through the comprehensive analysis of the data of the germination stage and seedling stage, it can be seen that the materials with better salt resistance are Zm4 and Zm32; the material with better alkali resistance is Zm30; the material with better salt and alkali resistance is Zm2. Through the application of comprehensive evaluation system, researchers can more effectively screen out maize germplasm resources with excellent genetic characteristics to promote maize variety improvement and genetic diversity protection.

Low temperature during early spring severely impairs maize germination, leading to significant yield losses. To elucidate the mechanisms underlying cold tolerance at the germination stage, we compared two cold-tolerant maize inbred lines (AM and CM) with a cold-sensitive line (BM) under control (25 °C) and chilling (6 °C) conditions. Phenotypic observations showed that AM and CM maintained high germination rates and exhibited enhanced coleoptile elongation under cold stress, whereas BM displayed substantial growth inhibition. Cold-tolerant lines accumulated less malondialdehyde and showed markedly higher SOD and POD activities, indicating a stronger antioxidant defense. Transcriptome profiling revealed that cold tolerance is associated with a more robust transcriptional response in AM and CM, characterized by significant activation of the phenylpropanoid and flavonoid biosynthesis pathways. Among the differentially expressed genes, the class III peroxidase gene ZmPER5 was strongly upregulated in AM and CM but only weakly induced in BM, suggesting its central role in reinforcing the cell wall structure and enhancing ROS-scavenging capacity under chilling conditions. Other lignin- and flavonoid-related genes, including ZmHCT4 and ZmCYP75, also exhibited genotype-specific induction patterns consistent with cold tolerance. qRT-PCR validation confirmed the RNA-seq expression trends. These results demonstrate that maize cold tolerance during germination relies on the coordinated enhancement of antioxidant enzyme activity, activation of phenylpropanoid-derived lignin biosynthesis, and accumulation of protective flavonoids. The identified candidate genes, especially ZmPER5, provide valuable targets for improving cold tolerance in maize breeding.

Members of the WRKY transcription factors (TFs) family play crucial roles in biotic and abiotic stress responses in plants, but their roles in response to drought stress in maize (Zea mays L.) have not been fully elucidated. Maize ZmWRKY82, a group IIc WRKY gene, was isolated from maize using reverse transcription polymerase chain reaction (RT-PCR). Using the UniProt online database, we found that ZmWRKY82 encodes a 222-amino protein with conserved WRKYGKK and C-X₄-C-X₂₃-H-X₁-H motifs. ZmWRKY82 is strongly induced by polyethylene glycol (PEG), abscisic acid (ABA), methyl jasmonate (MeJA), salicylic acid (SA), and ethephon (ETH) treatments. The ZmWRKY82 protein was located in the cell nucleus. ZmWRKY82 had transcriptional activation capability and was able to bind to the W-box element. ZmWRKY82-overexpressing Arabidopsis and maize exhibited stronger drought resilience, which was associated with enhanced antioxidant enzyme activity and altered transcription level of drought-related genes. These findings suggest that ZmWRKY82 plays a central role in conferring drought tolerance in maize and may contribute to crop improvement and sustainable agricultural practices.

Calmodulins (CaMs), which are important calcium-binding proteins, play critical roles in plant stress responses. However, limited information is available regarding the biological functions of CaMs under drought stress. In this study, we identified and isolated a CaM gene, ZmCaM2, from maize (Zea mays L.) in length and encodes a 184-amino acid protein containing four EF-hand domains capable of specifically binding calcium ions (Ca²⁺). Subcellular localization analysis revealed that ZmCaM2 is localized to the nucleus and membrane. Functional characterization indicated that ZmCaM2 negatively regulates drought tolerance in maize by increasing malondialdehyde (MDA) and reactive oxygen species (ROS) content while decreasing antioxidant enzyme activity, proline (Pro) content, abscisic acid (ABA) content and relative water content (RWC). Moreover, ZmCaM2 reduced maize sensitivity to ABA treatment, suggesting that ZmCaM2 negatively regulates the drought tolerance of maize by relying on the ABA pathway. These findings provide new insights into the functional role of ZmCaM2 and may facilitate the development of drought-resistant maize cultivars.