Saline‐alkali stress inhibited the normal growth and development of plants, which seriously restricted the yield of crops. Maize is one of the most important crops in the world. However, the mechanism of maize in response to saline‐alkali stress is still largely unknown. Through the observation of growth parameters and the detection of physiological and biochemical indicators in saline‐alkali tolerant (22KN3894) and saline‐alkali sensitive (H23146) maize inbred lines, this study found that compared with H23146, 22KN3894 accumulated less ROS content and more total flavonoids content, while the degree of root damage and ion toxicity was relatively small. Full‐length transcriptome and broadly targeted metabolome were used to analyse the response mechanism of extreme maize inbred lines to saline‐alkali stress. 22KN3894 accumulated more metabolites such as sugars and flavonoids. There were significant differences in the contents of flavonoid metabolites and genes related to flavonoid synthesis between the two materials. Weighted gene co‐expression network analysis and co‐expression network analysis based on RNA‐Seq data suggested that the ZmWRKY82 gene might respond to saline‐alkali stress by regulating the flavonoid biosynthesis pathway. ZmWRKY82 directly bound to the W‐box in the ZmCHI6 promoter and promoted its expression. The above results showed that ZmWRKY82 could improve the antioxidant capacity by promoting the transcription of ZmCHI6 and the synthesis of flavonoids, thereby resisting saline‐alkali stress. These findings provided novel insights for improving maize saline‐alkali stress tolerance, demonstrating that flavonoids played pivotal roles in plant stress adaptation, and laid the foundation for future mechanistic studies and breeding improvement.

Maize (Zea mays L.) is an annual gramineous herb and is among the world’s most important crop species. Drought is the main factor contributing to maize yield reduction. The lateral organ boundaries domain (LBD) proteins belong to a class of higher-plant-specific transcription factors. LBD proteins usually include the highly conserved lateral organ boundaries (LOB) domains that play essential roles in plant growth and response to biotic stresses. However, few studies have addressed the biological functions of LBD genes associated with maize response to drought. Here we cloned the ZmLBD2 gene from maize and described its role in combating drought. Investigating ZmLBD2 subcellular localization, we show that it localizes to the cell nucleus and can specifically bind with inverted repeats of “GCGGCG”. Under drought stress, Arabidopsis thaliana overexpressing ZmLBD2 performed better than the wild-type plants in terms of seed germination rates, root length, relative water content, fresh weight, chlorophyll content, proline content, and antioxidant enzyme content. Arabidopsis overexpressing ZmLBD2 contained less MDA, H₂O₂, and O2− than the wild-type plants. Our protein-protein interaction results indicate an interaction between the ZmLBD2 and ZmIAA5 genes. In conclusion, the ZmLBD2 gene positively regulates H₂O₂ homeostasis in plants, strengthening drought resistance.

Drought is among the most serious environmental issue globally, and seriously affects the development, growth, and yield of crops. Maize (Zea mays L.), an important crop and industrial raw material, is planted on a large scale worldwide and drought can lead to large-scale reductions in maize corn production; however, few studies have focused on the maize root system mechanisms underlying drought resistance. In this study, miRNA–mRNA analysis was performed to deeply analyze the molecular mechanisms involved in drought response in the maize root system under drought stress. Furthermore, preliminary investigation of the biological function of miR408a in the maize root system was also conducted. The morphological, physiological, and transcriptomic changes in the maize variety “M8186” at the seedling stage under 12% PEG 6000 drought treatment (0, 7, and 24 h) were analyzed. With prolonged drought stress, seedlings gradually withered, the root system grew significantly, and abscisic acid, brassinolide, lignin, glutathione, and trehalose content in the root system gradually increased. Furthermore, peroxidase activity increased, while gibberellic acid and jasmonic acid gradually decreased. Moreover, 32 differentially expressed miRNAs (DEMIRs), namely, 25 known miRNAs and 7 new miRNAs, and 3,765 differentially expressed mRNAs (DEMRs), were identified in maize root under drought stress by miRNA-seq and mRNA-seq analysis, respectively. Through combined miRNA–mRNA analysis, 16 miRNA–target gene pairs, comprising 9 DEMIRs and 15 DEMRs, were obtained. In addition, four metabolic pathways, namely, “plant hormone signal transduction”, “phenylpropane biosynthesis”, “glutathione metabolism”, and “starch and sucrose metabolism”, were predicted to have important roles in the response of the maize root system to drought. MiRNA and mRNA expression results were verified by real-time quantitative PCR. Finally, miR408a was selected for functional analysis and demonstrated to be a negative regulator of drought response, mainly through regulation of reactive oxygen species accumulation in the maize root system. This study helps to elaborate the regulatory response mechanisms of the maize root system under drought stress and predicts the biological functions of candidate miRNAs and mRNAs, providing strategies for subsequent mining for, and biological breeding to select for, drought-responsive genes in the maize root system.

Maize (Zea mays L.) is a widely grown food crop around the world. Drought stress seriously affects the growth and development process of plants and causes serious damage to maize yield. In the early stage, our research group conducted transcriptome sequencing analysis on the drought-resistant maize inbred line H8186 and screened out a gene with significantly down-regulated expression, Phylloplanin-like (ZmPL1). The ZmPL1 gee expression pattern was analyzed under various abiotic stresses, and the results showed that this gene was greatly affected by drought stress. Subcellular localization analysis showed that the protein was localized on the cell membrane. In order to verify the role of ZmPL1 in drought stress, we overexpressed ZmPL1 in yeast and found that the expression of ZmPL1 could significantly increase the drought sensitivity of yeast. Next, ZmPL1 transgenic plants were obtained by infecting maize callus using Agrobacterium-mediated method. Under drought stress, compared with overexpression lines, gene-edited lines had higher germination rate and seedling survival rate, lower accumulation of MDA, relative conductivity and ROS, higher antioxidant enzyme activity, and the expression levels of stress-related genes and ROS scavenging-related genes were significantly increased. Exogenous application of ABA to each lines under drought stress attenuated the damage caused by drought stress on ZmPL overexpressing plants. In summary, ZmPL1 negatively regulates drought tolerance in maize.

Maize (Zea mays L.) originates from the subtropical region and is a warm-loving crop affected by low-temperature stress. Dehydrin (DHN) protein, a member of the Group 2 LEA (late embryogenesis abundant proteins) family, plays an important role in plant abiotic stress. In this study, five maize DHN genes were screened based on the previous transcriptome sequencing data in our laboratory, and we performed sequence analysis and promoter analysis on these five DHN genes. The results showed that the promoter region has many cis-acting elements related to cold stress. The significantly upregulated ZmDHN15 gene has been further screened by expression pattern analysis. The subcellular localization results show that ZmDHN15 fusion protein is localized in the cytoplasm. To verify the role of ZmDHN15 in cold stress, we overexpressed ZmDHN15 in yeast and Arabidopsis. We found that the expression of ZmDHN15 can significantly improve the cold resistance of yeast. Under cold stress, ZmDHN15-overexpressing Arabidopsis showed lower MDA content, lower relative electrolyte leakage, and less ROS (reactive oxygen species) when compared to wild-type plants, as well as higher seed germination rate, seedling survival rate, and chlorophyll content. Furthermore, analysis of the expression patterns of ROS-associated marker genes and cold-response-related genes indicated that ZmDHN15 genes play an important role in the expression of these genes. In conclusion, the overexpression of the ZmDHN15 gene can effectively improve the tolerance to cold stress in yeast and Arabidopsis. This study is important for maize germplasm innovation and the genetic improvement of crops.