Molecular Pathogens, 2025, Vol.16, No.2, 69-76 http://microbescipublisher.com/index.php/mp 72 2017). In the interaction between corn and corn black powder bacteria, the bacteria also release some special proteins that can interfere with the immune response of corn. This shows that corn requires multiple disease-resistant genes to cope with complex pathogen invasion (Schurack et al., 2021). 4.2 Activation of signal transduction pathways When corn recognizes bacteria, a series of signal pathways will be opened to mobilize the defensive reaction in the body. Several important signaling molecules include salicylic acid (SA), jasmonic acid (JA), and abscisic acid (ABA). They regulate many genes related to disease prevention (Wang et al., 2016). For example, the gene ZmADT2 can help regulate metabolic processes, which is very critical to the synthesis of salicylic acid and lignin. These two substances are of great help to fight powdery bals (Ren et al., 2024). In addition, ZmWAK-RLK1 can also affect the level of a substance called benzooxazine. Reducing this substance helps to increase corn's resistance to large spot diseases (Yang et al., 2018). These examples all show that the secondary metabolism of corn is also involved in the process of fighting pathogens and is part of the rapid response of plants. 4.3 Role of defense-related genes in fungal resistance Many defense-related genes play a key role in corn fighting fungal diseases. Some genes help synthesize secondary metabolites such as terpenes and styrene, which rapidly increase after plants are infected with bacteria, helping to strengthen defense (Akohoue and Miedaner, 2022; Wang et al., 2022). In addition, some proteins (PR proteins) and antioxidant enzymes related to the course of the disease are also important. They can reduce the oxidative damage caused by bacteria, and can also make the cell wall stronger and less likely to be penetrated by bacteria (Maschietto et al., 2016). Studies have found that these defense genes are often continuously expressed in disease-resistant corn varieties. This shows that they may be the “core weapon” of corn to resist fungi such as Fusarium and Gibberine ear rot. At the same time, some people have found QTL (quantitative trait loci) related to these disease resistance, which provides a good reference for future disease resistance breeding. 5 Environmental and Agronomic Influences on Gene Expression 5.1 Effects of soil and environmental stress on resistance gene expression The disease-resistant genes of corn are affected by soil and environmental stress. For example, in the soil, the cell wall at the root is the first line of defense against invasion of bacteria (such as Fusarium). Resistant corn varieties have more cell wall-related genes and more lignin, which makes the roots stronger and more difficult to get infected (Quiroz-Figueroa et al., 2023). In addition, when oxidative pressure occurs in the environment, the expression levels of disease-resistant genes, such as PR genes, and antioxidant enzymes, will also change. Some disease-resistant corns are already active before the bacteria invade. This shows that they are “prepared” in advance to fight the disease (Lanubile et al., 2015). 5.2 Influence of agronomic practices on disease severity Field management methods will also affect the extent of corn’s illness. If we improve soil health and reduce environmental stress, the corn itself will be able to resist disease. For example, in some disease-resistant varieties, PR proteins and antioxidant enzymes can be expressed continuously themselves, which makes bacteria more difficult to invade (Maschietto et al., 2016). Choosing disease-resistant varieties in breeding is an effective and environmentally friendly way. This can reduce dependence on fungicides, and also reduce the problems of diseases and mycotoxins. Some studies have pointed out that if resistant varieties are not used, but chemical methods alone, the problem may be even worse (Lanubile et al., 2017). 5.3 Interaction between climate change and maize disease resistance Climate change changes the way bacteria move and also increases the risk of mycotoxin contamination, making corn's disease-resistant work harder. Pathogens like Fusarium may become more active under climate pressures, and the resistance mechanism of corn may also be affected. In order for corn to adapt to these changes, we need to understand its genetic basis, such as QTL (quantitative trait loci) and some key disease-resistant genes. These genes can regulate hormone signaling and defense responses in corn, and they can continue to help plants resist bacteria even if the environment changes (Yao et al., 2020).
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