Maize Genomics and Genetics 2025, Vol.16, No.3, 129-138 http://cropscipublisher.com/index.php/mgg 135 6.2 Application of heat-tolerant maize varieties Global warming has led to frequent high-temperature weather, which has severely restricted the growth and yield of corn. The development and application of heat-resistant corn varieties are of great significance to alleviate the negative effects of high temperature stress. The core of genetic improvement programs is to identify and utilize genetic variation to enhance heat tolerance. This includes germplasm screening, marker-assisted selection, genomic locus mapping and candidate gene identification. Genes related to heat tolerance and their regulatory networks are identified through genome assembly technology and integrated into breeding programs to cultivate more stress-resistant genotypes (Hill and Li, 2022). The application of transgenic technology, such as overexpression of specific transcription factors (such as ZmNAC074) encoding a positive regulator, activates the expression of ROS scavenging genes and HSR and UPR-related genes, and enhances the heat tolerance of plants under heat stress conditions (Xi et al., 2022). 6.3 Gene expression and phenotypic responses in case studies Studies on the transcriptional dynamics of maize under heat stress have shown that gene expression profiles change significantly, especially between heat-tolerant and sensitive inbred lines. For example, the more heat-tolerant inbred line CML 25 showed more significant differences in the expression regulation of heat stress-responsive genes compared with the sensitive inbred line LM 11. The expression changes of the most common HS-responsive genes were generally more significant in CML 25, which may be an important reason for the higher heat tolerance of CML 25 (Jagtap et al., 2023). The identification of differentially regulated genes and related pathways, such as those involved in endoplasmic reticulum protein processing, myricetin biosynthesis, and raffinose metabolism, further revealed the complex genetic response mechanism of maize to heat stress (Figure 3). In order to adapt to heat stress, the expression levels of thousands of genes are changed to rescue damage (Chen et al., 2023). Figure 3 Sketch map of the synthesis of myricetin. Red arrows indicate up-regulated protein and metabolites after heat stress, and green ones indicate the down-regulated protein. Values in the table represent the expression levels of Zm00001d047424 gene and its protein (Adopted from Chen et al., 2023)
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