Maize Genomics and Genetics 2025, Vol.16, No.4, 202-218 http://cropscipublisher.com/index.php/mgg 206 addition to HSF, members of the bZIP transcription factor family are also involved in the thermal response. Research has found that the expression of the bZIP factor ZmGBF1 in corn increases at high temperatures and can bind to G-box elements to regulate downstream genes. Cao et al. (2021) reported that ZmGBF1 enhanced the heat resistance of maize by activating the key gene ZmCXE2 of the GA pathway. ZmNAC074 of the NAC family has been demonstrated to enhance heat tolerance in transgenic Arabidopsis thaliana, suggesting that its function in corn may be to promote the expression of heat-resistant related genes. In fact, co-expression analysis revealed that multiple transcription factor family nodes were enriched in the maize high-temperature response gene network: AP2/ERF, MYB, bHLH, NAC, HSF, etc. were all directly or indirectly involved in regulating the high-temperature stress response. For instance, ZmWRKY106 has been reported to simultaneously enhance the drought resistance and heat resistance of corn. ZmNF-YC13, as a nuclear factor Y subunit, overexpression driven by high-temperature induced promoters can activate multiple heat-resistant genes and increase the survival rate of plants. These findings suggest that different transcription factors work together to form a complex regulatory network for corn in response to heat stress. Among them, on the one hand, there are "emergency commanders" like HSF that directly induce protective genes such as HSP; on the other hand, there are relay nodes like bZIP and NAC that integrate ROS, hormones and other signals and regulate the expression of a wide range of downstream genes. It is worth noting that one of the research hotspots of Chinese scholars is precisely the transcriptional regulatory mechanism of corn under heat stress, which will also be a key entry point for future heat-tolerant genetic improvement. 3.3 Potential roles of non-coding RNAs in transcriptional regulation under heat stress In addition to protein-coding genes, high-temperature stress can also cause significant changes in the expression profile of non-coding Rnas in corn, among which non-coding Rnas represented by micrornas (mirnas) play an important role in post-transcriptional regulation. miRNA is a type of 20-24 nt small RNA that mediates the cleavage or translation inhibition of target genes through base complementary pairing with target mrnas, thereby influencing gene expression levels. A large number of studies have shown that high temperatures can induce the up-regulation or down-regulation of miRNA expression in many plants and change the regulation of downstream stress-resistant genes. A variety of mirnas related to high-temperature responses have also been identified in corn. For instance, by using high-throughput sequencing, Qian et al. (2019) identified that approximately 40 mirnas, including miR156, miR159, miR160, and miR398, were significantly differentially expressed in the transcriptome under high-temperature stress at the seedling stage of maize. Among them, miR156 plays an important role in the high-temperature response of corn: its target is the SPL transcription factor family. Research has found that the specific upregulation of miR156 at high temperatures can inhibit the expression of the SPL gene, thereby enhancing the continuous expression of HSF and HSP and endowing plants with acquired heat-resistant "memory" ability. In contrast, the expression pattern of miR398 in corn differs from that in model plants: the expression changes of miR398 in corn under high-temperature stress are still uncertain, but in Arabidopsis thaliana, miR398 inhibits its target antioxidant enzyme genes such as CSD1 and CSD2, leading to the accumulation of ROS and the activation of the HF-HSP pathway, thereby enhancing heat tolerance. These speculations provide ideas for the function of corn miR398. Recent studies on corn hybrids have also shown that some mirnas may be involved in the regulation of pollen thermal sensitivity processes. For instance, miR159/319 indirectly affects male fertility by influencing auxin and GA pathways. In addition to miRNA, the role of long non-coding Rnas (lncrnas) in the high-temperature response of corn has also begun to attract attention. Du and Li (2024) summarized the functions of corn lncrnas in adverse conditions, pointing out that high temperatures can induce the expression of some lncrnas, which may act as molecular "sponges" to bind mirnas or recruit proteins, thereby regulating the expression of heat-resistant genes. For instance, it has been reported that certain lncrnas can form complexes with HSF, affecting its transcriptional activation efficiency for downstream HSP genes. Although the current understanding of the involvement of non-coding Rnas in the regulation of heat stress in maize is still relatively limited, there is already evidence suggesting that they are part of a complex gene regulatory network. In-depth exploration of the roles of miRNA and lncRNA in the heat tolerance of corn is not only expected to reveal new regulatory mechanisms, but also may provide novel heat resistance regulatory elements for molecular breeding. In
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