Maize Genomics and Genetics 2025, Vol.16, No.4, 202-218 http://cropscipublisher.com/index.php/mgg 215 7 Conclusions and Future Perspectives Recent studies have initially constructed a molecular regulatory map of corn's response to high-temperature stress. This study summarizes the multi-level mechanisms of high-temperature response in corn seedlings: From a physiological perspective, high temperatures lead to a decline in photosynthetic efficiency and an increase in respiratory loss in corn, disrupt the balance of reactive oxygen species and antioxidant systems within the body, and disrupt hormone levels, thereby inhibiting the normal growth and development of the plants. At the molecular level, corn alleviates heat damage by rapidly upregulating heat shock protein genes and activating genes related to antioxidant enzymes and protective substances. Meanwhile, multiple heat-response transcription factors (such as HSF, bZIP, NAC, etc.) synergistically regulate the transcription of downstream defense genes, forming a complex gene regulatory network. These transcriptional regulatory activities rely on the effective conduction of high-temperature signals within cells, including pathways such as Ca2+ transients, ABA and ROS signal mediation, and MAPK cascade amplification. Analysis of the gene co-expression network reveals that factors such as HSF are at the hub position of the maize heat response network, and many stress-resistant genes jointly constitute modular regulatory units. The gene expressions in different tissues and at different time stages are specific yet interrelated, ensuring the coordinated global and local heat resistance responses of plants. This study sorted out a large number of candidate heat-resistant genes identified by transcriptome technology and analyzed the action modes of some key genes (such as ZmHSF20, ZmGBF1, etc.) in combination with functional experiments. These achievements mark an important progress in the research on the high-temperature response mechanism of corn: a molecular map containing each link of "thermal perception - signal transduction - transcriptional regulation - physiological response" is gradually becoming clear. This map provides a framework for us to understand the genetic basis of corn heat tolerance and helps to subdivide heat tolerance traits into locatable and detectable molecular indicators (such as the expression level of specific genes, the content of specific metabolites, etc.). Overall, corn has demonstrated typical thermal response patterns, similar to model plants yet with its own characteristics: for instance, the HSF and HSP systems of corn function similarly to those of Arabidopsis thaliana, but as a C4 crop, corn has unique features in carbon metabolism regulation and organ-level responses (such as the issue of heat tolerance in the panicle). This knowledge laid the foundation for the next step of in-depth research. Although significant progress has been made in the research on the heat tolerance mechanism of corn, many problems remain unsolved and some technical challenges are also faced in the research. Firstly, in terms of genetic identification, although a large number of heat-tolerant related candidate genes have been discovered through transcriptome and association analysis, the functions of many of these genes remain unclear. For a crop like corn, which has a large genome and high functional redundancy, functional verification is rather difficult. At present, the number of key genes with verified functions is limited, and most candidate genes (especially non-coding Rnas and metabolic regulatory factors) still lack in-depth research. This leads to an incomplete understanding of the regulatory network of corn heat tolerance. Secondly, in terms of the regulatory mechanism, the signal crosstalk and coordination mechanism during the multi-level response process of corn remain unclear. For instance, how do signaling pathways such as Ca2+, ABA, and MAPK integrate with each other? Is there a cascade regulation or feedback loop among different transcription factors? These issues have only been reported sporadically so far, and systematic analysis still needs to be advanced. In addition, how to coordinate and unify the responses among different tissues and at different developmental stages is also a major challenge. Corn is a cross-pollinating crop, and its reproductive growth is extremely sensitive to heat. However, there are currently few studies on the correlation between heat tolerance during the vegetative growth period and the reproductive period, and there is still a lack of theoretical guidance on how to achieve heat tolerance improvement throughout the entire growth period. Secondly, in terms of breeding application, there is still a distance to go before the genes discovered in the laboratory can be applied to field varieties. Heat tolerance is a complex quantitative trait. The effect of a single gene is often limited, and it requires the aggregation of multiple favorable alleles to produce a significant improvement effect. However, multi-gene aggregation is prone to sacrificing other agronomic traits. How to improve heat tolerance while maintaining yield is a difficult point in breeding practice. In addition, high-temperature stress often occurs simultaneously with other adverse conditions such as drought. The heat and drought tolerance mechanisms of corn overlap and conflict (for example, closing stomata is beneficial for heat
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