Molecular Pathogens, 2025, Vol.16, No.5, 236-245 http://microbescipublisher.com/index.php/mp 238 encode NLR proteins. When the corresponding pathogenic effector proteins secreted by M. oryzae enter the cells, they are recognized by NLRs and activate downstream resistance responses. In addition to typical NLRs, there are also some pattern recognition receptor-type disease resistance genes in rice, such as the famous bacterial blight resistance gene Xa21. Xa21 encodes a transmembrane receptor kinase (RLK), which is located on the cell surface and can recognize specific signaling molecules secreted by pathogenic bacteria, thereby triggering a pattern-triggered immune (PTI) response. This type of PRR-type genes mediates broad-spectrum resistance, but the number is relatively small in rice (Huang et al., 2025). 3.2 Cell signal transduction and defense-related pathways When disease resistance genes recognize the invasion signal of pathogenic bacteria, they will trigger a series of downstream signaling cascade reactions, ultimately leading to the initiation of plant defense responses. In rice, several key defense signaling pathways include salicylic acid (SA), jasmonic acid (JA), and ethylene (ET)-dependent pathways, as well as reactive oxygen species (ROS) burst, calcium ion flow, MAP kinase cascade, etc. (Vidhyasekaran, 2020). Studies have shown that there is a division of labor in the signaling pathways induced by different pathogen types. The SA pathway mainly mediates resistance to trophic pathogens (such as Xanthomonas oryzae), while the JA and ET pathways are more involved in the resistance response to necrotrophic pathogens. In the rice defense response, early events include a transient influx of calcium ions and a burst of reactive oxygen species. Pathogen infection triggers the opening of calcium ion channels on the cell membrane, causing a sudden increase in cytoplasmic Ca2+ concentration, which acts as a second messenger to activate downstream components such as calcium-dependent protein kinase (CDPK). At the same time, ROS mediated by cell membrane NADPH oxidase accumulates at the infection site, causing allergic necrosis and signal amplification (Yamauchi et al., 2017). The signaling pathways of the three major hormones in rice also have complex crosstalk with each other. For example, studies on the interaction between rice and brown planthopper and Xanthomonas orbacterium bacterial blight found that there is an antagonistic effect between JA and SA signals. One biological stress may inhibit SA by activating JA, thereby affecting the resistance of another disease. 3.3 The role of epigenetic regulation and non-coding RNA in disease resistance Research in recent years has revealed that rice disease resistance is also subject to epigenetic regulation and fine control of non-coding RNA. At the epigenetic level, changes in DNA methylation and histone modifications can affect the expression status of disease resistance genes. For example, some studies have found that the antagonistic gene PigmS at the Pigm locus of the broad-spectrum blast resistance gene is regulated by DNA methylation (Figure 1). High methylation levels in its promoter region inhibit PigmS expression, thereby releasing its inhibition of PigmR-mediated resistance and achieving the coexistence of high resistance and high yield (Hoang et al., 2018; Wu and Fan, 2025). This epigenetic balance mechanism ensures that Pigm-carrying varieties have long-lasting blast resistance without sacrificing yield. It is an ingenious solution to the "disease resistance and growth trade-off" of natural evolution. In terms of non-coding RNA, small RNA and long non-coding RNA (lncRNA) are also involved in the regulation of disease resistance immunity in rice. For example, ALEX1, a long non-coding RNA, was found to be significantly induced in response to bacterial blight infection. ALEX1 interacts with the Auxin response factor ARF3 to promote the activation of the jasmonic acid pathway, thereby improving resistance to bacterial blight. Transgenic rice overexpressing ALEX1 showed increased endogenous JA levels and reduced bacterial blight lesions (Wei et al., 2017). 4 Combination of Traditional Breeding and Molecular Breeding Technology 4.1 Identification and utilization of disease-resistant germplasm resources Rich germplasm resources are the cornerstone of disease resistance breeding. Rice cultivars and wild relatives contain many useful disease resistance genes. Traditional breeders have long collected disease-resistant germplasm around the world and systematically carried out resistance identification. For example, in the blast
RkJQdWJsaXNoZXIy MjQ4ODYzNA==