Maize Genomics and Genetics 2025, Vol.16, No.6, 325-333 http://cropscipublisher.com/index.php/mgg 326 This study aims to clarify the dynamics of DNA methylation in maize root systems under salt stress and combines the latest advancements in high-resolution methylomics and functional genomics, including: (1) characterizing the changes in genome-wide methylation at different salt concentrations; (2) Identify the key methylation regulatory genes and pathways involved in root adaptation; (3) Evaluate the potential of epigenetic markers in breeding salt-tolerant corn varieties. This research will lay the foundation for developing innovative strategies to enhance the stress resistance and productivity of corn under salt stress. 2 Physiological and Molecular Responses of Maize Roots to Salt Stress 2.1 Root architecture and osmotic adjustment mechanisms When exposed to salt stress, the changes in some corn roots are quite obvious, especially for those varieties that are not very salt-tolerant to begin with - shortened root length and reduced lateral roots. Such phenomena can often be observed (Li et al., 2021). However, not all varieties will never recover. For instance, some salt-tolerant types may instead show structural "self-rescue" reactions such as thickened roots, enlarged cortical cells, and even the growth of ventilation tissues (Hu et al., 2022). Such adjustments seem to be made to reduce the burden and maintain the vitality of the roots. Sometimes, even if the development of the main root is restricted, the overall biomass of the root system can still be maintained roughly. When it comes to regulating water, some strains accumulate a considerable amount of proline and betaine at the root tip. These small molecule solutes help maintain turgor pressure and allow cells to "hold on" (Hajlaoui et al., 2010). But ultimately, it's not just water regulation that sustains the root system; ion balance is even more crucial. Some corn relies on a mechanism of "salt excretion and potassium retention" - Na+ can be rapidly excreted while K+ remains relatively stable. This usually involves the participation of transport proteins such as ZmHKT1, ZmHAK4, and ZmNHX1 (Zhang et al., 2021). It is precisely these details of regulation that have widened the gap between varieties in terms of whether they can survive in saline-alkali land. 2.2 Antioxidant systems and signal transduction under salt stress When it comes to salt stress, reactive oxygen species (ROS) is an unavoidable issue. When there is too much of it, root cells are prone to damage. However, the reactions of different corns to it vary greatly. Some varieties have strong antioxidant systems and can "withstand" it. Some are not so good (Ahmad et al., 2020). The activity levels of antioxidant enzymes such as SOD, CAT, POD and GST have become important references for measuring salt tolerance. Generally speaking, for those salt-tolerant genotypes, the activity of these enzymes is usually high, and the damage to the cell membrane is also less - the content of malondialdehyde is much lower. If the problem of ROS is not solved merely by clearing it, the entire set of signal mechanisms that follow must also keep up. Pathways such as ABA, auxin, and MAPK are "activated" at the very beginning of stress, responsible for regulating downstream gene expression, coordinating water, restoring metabolism, and protecting cells (He et al., 2024). These mechanisms are not for temporary coping but more like a contingency plan left by plants over a long period of time. Whether the stress can be transformed into an opportunity for survival depends crucially on the stability of this link. 2.3 Gene expression regulation and preliminary epigenetic responses When salt stress occurs, a large number of genes in the root system will always undergo expression changes. Some studies have listed tens of thousands of DEGs, mainly focusing on pathways such as ion transport, hormone response, and ROS clearance (Maimaiti et al., 2025). However, not all responses rely on genes "fighting alone". In fact, there is a complex regulatory network behind it. The participants include transcription factors such as WRKY, bZIP, MYB, bHLH, as well as non-coding components such as miRNA and lncRNA (Liu et al., 2022). In the early stage of stress, the response is mostly rapid regulation, while in the later stage, the goal of the genetic network leans towards metabolic balance and growth recovery. In addition, there is preliminary evidence suggesting that these expression changes are not entirely "transient memory". Epigenetic mechanisms such as DNA methylation and histone modification are likely to have played a stabilizing regulatory role in them, providing a longer-term "genetic account" for stress adaptation (Figure 1) (Eprintsev et al., 2024).
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