Molecular Pathogens, 2025, Vol.16, No.2, 53-60 http://microbescipublisher.com/index.php/mp 55 the StMKK5-StSIPK module can activate the SA pathway, which is very important for potatoes to resist this bacteria. StMKK5 is a kinase that works with StSIPK and can trigger programmed cell death (also called HR) by initiating SA signals, thereby preventing bacteria from spreading. When StMKK5 or its downstream gene SIPK is “silenced”, the HR response triggered by INF1 becomes weaker. This suggests that this module is important for SA-mediated immune responses. If there is a problem with StMKK5, such as a mutation, the HR reaction will also disappear, indicating that its kinase activity is critical. Even if StMKK5 is overexpressed, the lesions area does not change much compared with the control group, indicating that the SA signal is also regulated by other signals (Figure 1) (Yang et al., 2023). In addition, other pathways such as SA and ethylene also interact to make defense more complicated (Fantino et al., 2017). Figure 1 Overexpression of potato StMKK5 triggers a SIPK-dependent plant cell death in Nicotiana benthamiana (Adopted from Yang et al., 2023) 4.2 Synergistic action of the jasmonic acid-ethylene pathway The two signal pathways, jasmonic acid and ethylene, often cooperate to help potatoes defend against bacteria, especially when fighting Phytophthora infestans. Research has found that spraying ethylene in disease-resistant potatoes can stimulate a defensive response, which shows that ethylene not only works on its own, but is also related to other hormones such as JA. The relationship between these two hormones is complex. Sometimes they cooperate to enhance resistance, but sometimes they may also inhibit each other, such as when controlling certain defense genes or protein kinases (Yan et al., 2022). 4.3 Role of reactive oxygen species (ROS) in signaling pathways Reactive oxygen species (ROS) is also a very critical ingredient in potato disease prevention. It can quickly activate defenses, such as triggering hypersensitivity reactions or hardening the cell walls. In potatoes, reactive oxygen species like H₂O₂ are produced quickly. A protein called StRac1 regulates the level of H₂O₂, thereby enhancing resistance (Zhang et al., 2020). ROS can also work with signal molecules like SA to produce stronger defense effects. This also shows that ROS plays an important role in the immune signal of plants (Zheng et al., 2020). 4.4 Functions of signaling proteins (e.g., MAPKs, NLR proteins) Some proteins are also important in potato disease prevention, such as MAPK (migen-activated protein kinase) and NLR (proteins with nucleotide binding and leucine repeat structures). For example, the MAPK module StMKK5-StSIPK can activate the SA and ethylene pathways to make potatoes more resistant to disease (Chen et al., 2021). Another protein, StMPK7, is downstream of StMKK1, which also enhances resistance through SA signaling (Liu, 2024). These proteins can integrate signals from different pathways to regulate defense responses, thereby dealing with pathogens more effectively.
RkJQdWJsaXNoZXIy MjQ4ODYzNA==