Molecular Microbiology Research, 2025, Vol.15, No.2, 82-92 http://microbescipublisher.com/index.php/mmr 87 4.2 Signal transduction regulatory mechanism in the resistance pathway 4.2.1 Interaction between salicylic acid and jasmonic acid pathways In the rice immune system, salicylic acid (SA) and jasmonic acid (JA) are two key signal pathways. SA is usually associated with resistance to dicotyledonous parasitic pathogens such as bacterial blight, while JA is mainly involved in responding to saprophytic pathogens such as sheath blight (Deng et al., 2020). However, unlike Arabidopsis, the SA and JA pathways in rice are not completely antagonistic, but have a complex relationship of synergistic regulation (Zhang et al., 2020). Studies have found that SA can induce the expression of disease resistance genes such as WRKY45 and PR1, while JA can activate defense factors such as OsERF1. When infected by certain diseases (such as rice blast), the SA and JA pathways may be upregulated simultaneously to form a complementary immune system (Iwai et al., 2007). In recent years, key nodes that regulate the interaction between these two pathways have attracted attention. For example, OsNPR1 can achieve coordinated control between different hormone pathways, and its enhanced expression can improve overall disease resistance (Zhang et al., 2020). In addition, some transcription factors such as OsWRKY28 and OsEIL3 have also been found to have the ability to regulate SA/JA balance. Zhu et al. (2024) found that OsEIL3 regulates the expression of OsWRKY28 and OsERF40 during rice blast infection, coordinates the SA and JA signaling pathways, and thus affects the resistance response of rice to different pathogens. 4.2.2 Role of resistance-related transcription factors Transcription factors are key to rice immune regulation. The WRKY family, especially OsWRKY45, is central to SA-mediated resistance and helps against bacterial blight and blast (Shimono et al., 2007). OsWRKY45 is controlled by OsNPR1 and activates defense genes while balancing growth (Inoue et al., 2013). Other families like bZIP, ERF, and NAC also play roles. OsERF922 is a negative regulator of blast resistance; its knockout increases immunity (Wang et al., 2016). OsNAC4 controls cell death during hypersensitive responses (Kaneda et al., 2009). These factors bind to promoters of resistance genes and help regulate downstream signaling. Interactions among networks are common. For example, OsWRKY13 can activate SA and suppress JA, helping coordinate multi-disease resistance (Qiu et al., 2020). Understanding these networks allows better control of immunity and growth in breeding. 4.2.3 Functional role of miRNAs in disease resistance MicroRNAs (miRNAs) act as fine-tuners in plant immune responses. They target transcription factors or signaling genes to control the timing and strength of defense (Campo et al., 2021). In rice, osa-miR156 and miR159 are negative regulators. miR156 targets SPL genes and weakens defense during bacterial blight (Lu et al., 2021), while miR159 reduces blast resistance by silencing GAMYB (Chen et al., 2021). In contrast, miR160 and miR398 enhance blast resistance (Li et al., 2014; Li et al., 2019). Gene editing and target mimicry are now used to control miRNA levels. For example, blocking miR530 through a mimic (MIM530) improves resistance, maturity, and yield (Li et al., 2021). Other miRNAs like miR827 and miR444 link immunity and phosphorus signaling, making them promising targets (Hou et al., 2022). 5 Application of Molecular Breeding Strategies in Disease Resistance Breeding 5.1 Development of marker-assisted selection (MAS) technology Marker-assisted selection (MAS) is a useful tool in crop breeding, linking molecular markers closely with target genes. It plays an important role in speeding up rice disease resistance breeding. Compared to traditional phenotype-based selection, MAS is efficient, accurate, and repeatable, which helps shorten the breeding cycle and improve selection accuracy (Babu et al., 2020).
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