Maize Genomics and Genetics 2025, Vol.16, No.4, 202-218 http://cropscipublisher.com/index.php/mgg 203 gene editing techniques also provide possible approaches for precisely improving the heat tolerance traits of corn (Razzaq et al., 2021; Pandey et al., 2024). In particular, omics technologies such as transcriptomics can identify key genes and regulatory elements in response to high temperatures in high throughput, accelerating the development of heat-resistant related molecular markers and the cloning of candidate genes. The achievements of research on the molecular mechanism of heat response have demonstrated application potential in corn breeding: for instance, quantitative trait loci (QTLS) and associated markers for identifying heat tolerance in corn can be used in heat-resistant molecular breeding. The cloned heat-regulating genes can be used for transgenic methods to enhance the stress resistance of crops. It can be foreseen that an in-depth analysis of the signal transduction and gene regulatory network of corn in response to high-temperature stress will provide important genetic resources and theoretical guidance for the breeding of new heat-tolerant corn varieties. This study focuses on the response mechanism of corn seedlings to high-temperature stress. Based on the latest research progress, it systematically reviews the physiological responses, transcriptional regulatory characteristics, and molecular network mechanisms of corn under high-temperature stress. This study first introduces the adverse effects of high temperature on the growth and development of corn seedlings and the stress response, laying a foundation for understanding the subsequent molecular mechanisms. Then, it focuses on summarizing the expression characteristics of genes related to corn heat response, including the role of the heat shock protein (HSP) family, heat response transcription factors, and non-coding Rnas, and elaborates on the pathways and molecular networks by which corn perceives and transmits high-temperature signals. Special attention was paid to typical signaling pathways such as Ca2+, abolic acid (ABA), and mitogen-activated protein kinase (MAPK). Then, the differences in gene expression in different tissues and at different times were compared to analyze the tissue specificity and temporal dynamic patterns of heat stress responses in maize. On this basis, summarize the potential candidate genes and their regulatory patterns identified through transcriptome analysis, and explore the application prospects of these genes in heat-tolerant breeding. This study aims to construct a molecular map of corn's high-temperature response, deepen the understanding of the heat tolerance mechanism of corn, provide a scientific basis for improving the heat tolerance traits of corn, and also offer reference value for the heat resistance research of other crops. 2 Physiological Responses of Maize Seedlings to Heat Stress 2.1 Disruption of photosynthesis and respiration caused by high temperatures The most direct impact of high-temperature environments on corn seedlings is manifested in the decline of photosynthetic efficiency and the disorder of respiratory metabolism. Under suitable temperatures, corn synthesizes a large amount of assimilates through photosynthesis for growth and development. However, when the temperature suddenly rises above 35 ℃, the stomata on the leaves close excessively to reduce water loss, resulting in a significant decrease in the rate of carbon dioxide assimilation. Research has found that high-temperature stress can damage the structure and function of photosystem II (PSII), reduce the photochemical quantum yield, and cause adverse changes in chlorophyll fluorescence parameters (Doğru, 2021). Meanwhile, high temperatures accelerate the rate of corn respiration, causing excessive consumption of a large amount of carbohydrates and generating excessive free radicals and other by-products, which further inhibit the photosynthesis process. For instance, when comparing two corn varieties with different heat tolerations, it was found that under high-temperature treatment, the net photosynthetic rate (Pn) and chlorophyll content of the sensitive variety decreased much more than those of the heat-tolerant variety, while the intensity of respiratory oxygen release abnormally increased (Wang et al., 2024). High temperatures also cause changes in leaf structure: leaves become thinner and the density of stomata decreases, thereby reducing photosynthetic capacity. High temperatures interfere with the photosynthetic electron transfer and carbon assimilation processes of corn seedlings by affecting stomatal behavior and the photosynthetic membrane system, and also enhance respiratory decomposition. Together, these two factors lead to insufficient accumulation of photosynthetic products and hinder plant growth. 2.2 Accumulation of reactive oxygen species (ROS) and activation of antioxidant defense systems High temperature stress often leads to excessive accumulation of reactive oxygen species (ROS) in corn seedlings, putting the cells in an oxidative stress state. High temperatures can disrupt the normal function of the electron
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