Maize Genomics and Genetics 2025, Vol.16, No.6, 294-303 http://cropscipublisher.com/index.php/mgg 298 As for ZmDREB2A, it is activated almost "instantly" when drought strikes, and then regulates a series of downstream stress genes, enabling plants to maintain homeostasis in adverse conditions (Gulzar et al., 2021). The discovery of these genes not only explains the different performances of corn under drought conditions, but also provides a practical basis for subsequent targeted improvement using CRISPR/Cas9. 5 Case Study: Field Application of CRISPR-Edited Maize Lines 5.1 Description of editing strategy and target gene(s) Among the numerous attempts at corn gene editing, ARGOS8 is a target that has been repeatedly mentioned. It was originally a negative regulatory factor for the ethylene reaction. That is to say, once its expression level is adjusted, it can indirectly affect the plant's response to stress. Researchers used the CRISPR/Cas9 tool to precisely modify ARGOS8: some inserted the natural GOS2 promoter in its 5 'untranslated region, while others replaced the original promoter with this promoter (Bashir et al., 2021). These treatments enable the genes to be continuously highly expressed in multiple tissues. After all the modifications were completed, the researchers verified them one by one through PCR and sequencing, confirming that the ARGOS8 site had undergone the expected changes. Although the steps are complex, this idea of "promoter replacement" provides a new entry point for the functional improvement of corn. 5.2 Comparative evaluation: edited vs. wild-type lines under controlled drought conditions The real test is not in the laboratory but in the field. The research team planted the CRISPR-edited ARGOS8 strain under both drought and normal irrigation conditions, and used the wild type (WT) as a control. It was found that the edited plants showed stable performance under drought stress during the flowering period, and the transcriptional level of ARGOS8 significantly increased (Namata et al., 2025). Agronomic traits, especially grain yield, are closely monitored-the edited plants not only have enhanced drought resistance but also maintain good yield. Meanwhile, similar strategies have also been applied to the modification of other drought-related genes, such as ZmPL1 and ZmGA20ox3. The researchers respectively evaluated the responses of these plants at the physiological and biochemical levels, and the results also showed positive effects. It can be said that these experiments have truly brought CRISPR from a "laboratory tool" to "farmland application". 5.3 Results and interpretation: improved growth, yield, and stress marker expression Under drought stress conditions, the ARGOS8 editing strain performed significantly better than the wild type. Field data show that the average yield per unit area increased by approximately 5 bushels, while no negative impact was observed under conditions of adequate moisture (Wang et al., 2024). More detailed observation revealed that the physiological indicators of the edited strain were also more ideal-water loss was slower, reactive oxygen species (ROS) accumulated less, and antioxidant enzyme activity was higher. Similar improvement effects have also emerged in other gene-edited strains. For example, the plants edited with ZmPL1 showed improvements in germination rate and survival rate (Figure 2), while the contents of MDA and ROS decreased and the expression of stress-related genes was stronger (Wang et al., 2025). The ZmGA20ox3 edit strain exhibits an interesting "semi-dwarf" characteristic, which is often accompanied by higher levels of abscisic acid (ABA) and jasmonic acid (JA). They still maintained good yields under drought (Liu et al., 2023). Overall, these results indicate that corn regulated by CRISPR can not only "live better" but also "produce more", providing a practical molecular pathway for drought-resistant breeding. 6 Impacts of Gene Knockouts on Drought Tolerance 6.1Alterations in root system architecture and stomatal regulation When plants are in drought, the first to "react" are not the leaves but often the roots and stomata. Gene knockout can precisely bring profound changes in these two aspects. Taking corn as an example, researchers knocked out the DSD1/ZmICEb gene using CRISPR/Cas9 technology. As a result, stomatal density decreased, water use efficiency improved, and yield loss under stress was significantly reduced (Zhou et al., 2025).
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