Maize Genomics and Genetics 2025, Vol.16, No.3, 108-118 http://cropscipublisher.com/index.php/mgg 115 In order to verify the performance of the ZmHSF20 regulatory mechanism in actual agricultural environments, the researchers subjected Zmhsf20 mutants, ZmHSF20 overexpression lines and wild types under different genetic backgrounds to field heat stress treatment and systematic evaluation. The results showed that under continuous high temperature environment, the performance of Zmhsf20 mutants was significantly better than that of wild types, and their pollen vigor, fruit set rate, 1000-grain weight and yield retention ability were significantly enhanced. At the same time, physiological parameters such as leaf photosynthetic efficiency, antioxidant enzyme activity and cell membrane integrity also showed that the mutants had stronger high temperature adaptability. Further studies revealed that ZmHSF20 indirectly affected the expression of cell wall construction-related genes such as ZmPAL1 by inhibiting the expression of its downstream regulatory factors ZmHsf4 and cellulose synthase gene ZmCesA2, thereby regulating cell wall stability. Enhanced expression of ZmHSF4 and ZmCesA2 can improve cell wall stability and heat resistance. Double mutant experiments (Zmhsf20-1/Zmhsf4-1) verified the key role of ZmHsf4 downstream of ZmHSF20, which manifested as heat-resistant growth advantage in the field. 6.3 Integration of molecular and agronomic strategies for climate-resilient maize In the study of high temperature stress, identifying and regulating stress response genes and their signaling pathways has become an important means to improve heat tolerance. ZmNAC074 is a typical stress-responsive gene in the maize NAC transcription factor family. Xi et al. (2022) found that it encodes a membrane-bound transcription factor (MTF) that may be located on the membrane. Under various abiotic stress conditions, the expression level of ZmNAC074 in leaves was significantly upregulated, especially under high temperature stress. This suggests that ZmNAC074 may play a core role in plant heat stress signal transduction and defense system. Through functional verification experiments of transgenic Arabidopsis, the researchers further revealed the regulatory pathway of ZmNAC074: ZmNAC074 overexpressing plants showed stronger heat tolerance under heat stress, and this phenomenon was closely related to changes in the content of a series of stress metabolites. Overexpression plants accumulated more antioxidants (such as proline, soluble proteins, and carotenoids), while reducing the accumulation of ROS and membrane lipid peroxidation products (MDA), thereby improving cell membrane stability and antioxidant capacity. Real-time quantitative PCR analysis showed that overexpression of ZmNAC074 could significantly activate multiple genes related to heat stress response (HSR) and endoplasmic reticulum stress response (UPR), especially ROS scavenging-related genes (such as GPX and APX), indicating that ZmNAC074, as a positive regulator of heat stress, plays a core regulatory role in enhancing plant heat resistance. Wild relatives are plant species that are highly similar to the maize genome and can even hybridize with each other. They play an important role in maize breeding. First, in terms of increasing the germplasm diversity of maize, wild relatives can provide new unlimited potential for maize breeding. Wild relatives also have good disease resistance and stress resistance, and have broad application prospects in maize variety improvement (Jamil et al., 2024). By combining these molecular insights with traditional breeding techniques, it may be possible to develop maize varieties that are more resilient to the challenges of climate change. 7 Technological Innovations for Enhancing Heat Tolerance in Maize 7.1 Activation of endogenous regulatory mechanisms In the technical path of improving the heat tolerance of corn, activating the endogenous regulatory mechanism of plants is becoming a new research and application focus. Compared with traditional exogenous physical protection or cultivation adjustment strategies, endogenous signal molecule regulation has the advantages of systematic, continuous, low-cost and high-efficiency. Among them, salicylic acid (SA), as one of the core signal molecules in the response of plants to abiotic stress, has been increasingly valued in regulating the heat stress defense mechanism. The latest research results of Yangzhou University took glutinous corn as the research object, and for the first time systematically revealed the regulatory mechanism of salicylic acid in improving the heat tolerance of corn through the combined analysis technology of transcriptome and metabolome. The study found that salicylic acid treatment can significantly induce the expression of a series of genes related to high temperature stress response, including
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