Molecular Microbiology Research, 2025, Vol.15, No.1, 28-36 http://microbescipublisher.com/index.php/mmr 30 disease (Yang et al., 2023). There are also some genes involved in the synthesis of secondary metabolites like scopolamine. These metabolites can inhibit the growth of Fusarium oxysporum and help sweet potatoes improve resistance (Kim et al., 2023). Finding these genes is particularly helpful in breeding disease-resistant varieties and also provides clear targets for sweet potato breeding. 3.3 Transcription factors and regulation of resistance gene expression (WRKY, MYB, etc.) WRKY, MYB and NAC, these types of transcription factors play an important role in regulating disease-resistant genes. They can affect some signaling pathways, such as those associated with salicylic acid (SA) or jasmonic acid (JA). These signaling pathways are critical in plant disease prevention responses (Smith, 2024). Studies have pointed out that WRKY performs particularly well against Fusarium fungi. The expression of these transcription factors increases significantly after pathogen infection, indicating that they play an important role in sweet potatoes' resistance to biological stress (Li et al., 2023). 3.4 Cloning and functional validation of resistance genes To enhance the disease resistance of sweet potatoes, you must first find out those useful disease resistance genes. To this end, scientists have used many methods, such as transcriptome analysis and genome-wide association study (GWAS), to screen out candidate genes. Some studies overexpress the IbINV gene of sweet potatoes, and it was found that it can increase the resistance of sweet potatoes to black rot by regulating sugar metabolism (Yang et al., 2023). In addition, some people have tried to use CRISPR-Cas13 technology to enhance the antiviral ability of sweet potatoes. This technique can directly “cut off” key parts of the virus, thereby protecting plants (Yu et al., 2021). These new methods not only help us understand how sweet potatoes resist diseases, but also provide many useful ideas for future cultivation of disease-resistant varieties. 4 Signal Transduction Pathways in Sweet Potato Pathogen Response 4.1 Role of salicylic acid (SA) pathway in disease resistance Salicylic acid (SA) is very critical in the process of preventing diseases of sweet potatoes. The study found that when sweet potatoes are infected, the SA pathway is activated. At this time, some "course-related genes" (PR genes) will be activated, which can enhance the plant's disease resistance. For example, some studies used Bacillus amyloliquefaciens YTB1407 to treat sweet potatoes, and found that the SA content in the sweet potatoes was significantly increased, and genes such as PR-1 were also expressed more. The result was that sweet potatoes had increased resistance to fungi such as Fusarium solani and Ceratocystis fimbriata (Wang et al., 2020). In addition, some studies have found through transcriptome analysis that the SA pathway is also helpful in fighting viruses, which further demonstrates that it plays an important role in plant disease resistance (Bednarek et al., 2021). 4.2 Jasmonic acid (JA) and ethylene (ET) pathways in defense response In addition to SA, sweet potatoes also use jasmonic acid (JA) and ethylene (ET) pathways to defend against diseases. There is a transcription factor called IbBBX24, which is an important regulatory protein in the JA pathway. It can help plants synthesize more JA and also allow relevant signals to pass faster. Experiments show that after overexpressing IbBBX24, sweet potatoes accumulate more JA, and their ability to resist Fusarium oxysporus is also enhanced, without affecting yield (Zhang et al., 2020 ). In addition, during bacterial invasion, some disease-resistant varieties of sweet potatoes activate MAPK signal chains associated with ethylene, indicating that ethylene also plays a role in defense (Duan et al., 2019). 4.3 Roles of other signaling molecules (e.g., ABA, H2O2) in disease response In addition to the above mentioned types, sweet potatoes also use other signal molecules to prevent diseases, such as abscisic acid (ABA) and hydrogen peroxide (H₂O₂). During stem nematode infection, the synthesis process of ABA is initiated. This can increase the resistance of sweet potatoes to pests (Qiao et al., 2023). H₂O₂ is a reactive oxygen species that also plays the role of signaling molecules in the immune response of plants. Studies have found that after treating sweet potatoes with Bacillus amyloliquefaciens YTB1407, the H₂O₂ level in the roots decreased. This shows that it may be regulating the oxidative pressure of plants and helping sweet potatoes relieve
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