Molecular Pathogens, 2025, Vol.16, No.2, 53-60 http://microbescipublisher.com/index.php/mp 56 5 Interaction Between Signaling Pathways and Resistance Genes 5.1 Activation and regulation of resistance genes To start the disease-resistant gene in potatoes, some signaling pathways need to be used to “help”. For example, the MAPK cascaded pathway (modules like StMKK5-StSIPK) can activate two important signal pathways, salicylic acid (SA) and ethylene (ET). This is critical to increasing potato resistance to Phytophthora infestans. This module mainly triggers cell death by phosphorylating StSIPK, that is, “turning on the switch”, which is actually a way of defense. This process can also activate a series of genes related to SA and ET (Yang et al., 2023). In addition, ethylene can also stimulate the immune response of potatoes. Studies have found that under ethylene treatment, the expression of some specific transcription factors and kinases will change. This shows that in the defense reaction, hormones will also affect each other, forming a relatively complex network. 5.2 Effector-triggered immunity (ETI) involving Rgenes Effector-triggered immunity, referred to as ETI, is an important mechanism for plant disease prevention and usually depends on the R gene. In potatoes, StMPK7 in the MAPK signaling pathway is a downstream member of StMKK1, which plays a big role in combating late blight. StMPK7 can be activated after being phosphorylated, and then it can enhance resistance through SA signal. This also shows that R genes play a central role in ETI (Chen et al., 2021). There is also a protein called StRac1 that is also very important. It can regulate the production of reactive oxygen species (H₂O₂), which is one of the common defense methods in ETI reactions. 5.3 Case study: The Rpi gene family in late blight resistance Rpi is a highly studied potato disease-resistant gene, specifically used to fight late blight caused by Phytophthora infestans. These genes work with a variety of signaling pathways, including hormone pathways such as SA, JA, and ET. These pathways cooperate with each other to help activate defense responses faster and more efficiently. In some disease-resistant varieties, the SA pathway is particularly active, with significantly increased expression of defense genes such as EDS1 and PR-1, which is very critical for late blight disease (Zhang et al., 2020). These studies also show that the coordination between the Rpi gene and different signaling pathways is very complex. This cross-regulation mechanism allows plants to make corresponding adjustments according to different bacteria and improve overall resistance. 6 Case Study: Signaling Regulation in Potato Late Blight 6.1 Phytophthora infestans infection process and induced signaling responses Phytophthora infestans is the pathogen that causes late blight. It attacks some important signaling pathways in the potato body, causing infection. It suppresses the salicylic acid (SA) pathway through an effector called Pi06432, which is important to the plant's immune system. Pi06432 targets a protein called StUDP, which has a ubiquitin-like domain in potatoes. Pathogens use this to reduce the activity of the proteasome, which will also make a transcription factor called SARD1 unstable, and ultimately reduce SA synthesis, and the plant s defense will become weaker (Wang et al., 2023). However, during the infection, the abscisic acid (ABA) signal is also activated. There is a non-coding RNA called StlncRNA13558, which can promote the production of reactive oxygen species (ROS) and affect the SA pathway, thereby improving disease resistance. Experiments have found that if the RNA is overexpressed, the expression of the StPRL gene will also be significantly improved; and if StPRL is inhibited, the resistance will become worse. In addition, the expression of StlncRNA13558 and StPRL can also be increased after ABA application, making the plant more resistant. This shows that this RNA can trigger local immunity by allowing ROS to accumulate, and also plays an important role in signaling and cell death (Figure 2) (Shang et al., 2024). 6.2 Roles of salicylic acid and jasmonic acid pathways in late blight resistance The two pathways, salicylic acid (SA) and jasmonic acid (JA), are both critical in fighting late blight. The StMKK5-StSIPK module in potatoes can activate the SA and ethylene (ET) pathways, which can strengthen defenses and initiate programmed cell death to prevent bacteria from spreading. There is also a transcription factor called StbZIP61, which regulates SA synthesis by binding to StNPR3L. It only works in the presence of SA,
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