Molecular Microbiology Research, 2025, Vol.15, No.2, 69-81 http://microbescipublisher.com/index.php/mmr 74 In recent years, Host-Induced Gene Silencing (HIGS) has gained increasing attention as a new direction of transgenic technology. Wang et al. (2024) constructed cotton expressing V. dahliae pathogenic gene siRNA. The results showed that the pathogen showed a significant decrease in effector protein expression after contact, and the plant disease index decreased by more than 40%. HIGS technology has the advantages of strong specificity and controllable targets, and is suitable for integrated application with disease-resistant varieties. 5 Case study: Development of Verticilliumwilt-Resistant varieties 5.1 Functional study of GhLAC15gene in disease-resistant varieties In the study of cotton resistance to Verticilliumwilt, GhLAC15 was found to be a laccase gene closely related to resistance. The expression level of this gene in the disease-resistant variety Jimian20 was significantly higher than that in the susceptible material, especially in the early stage of pathogen infection, when its transcriptional activity increased rapidly (Zhang et al., 2019). The laccase protein encoded by GhLAC15 is involved in lignin synthesis and cell wall reinforcement, and is believed to be able to effectively block the spread of pathogens in vascular tissues. To verify its function, the research team constructed transgenic plants overexpressing GhLAC15 in Arabidopsis. After inoculation with Verticillium wilt, these transgenic plants showed significant resistance enhancement: the lesion area was reduced, the leaves remained upright, and the overall growth state of the plants was better than that of the wild-type control (Figure 2). The figure intuitively shows that the disease index of the GhLAC15 overexpression group decreased significantly within 10 days after infection, supporting its positive role in plant disease resistance. In contrast, after the expression of GhLAC15 was inhibited by virus-induced gene silencing (VIGS), the originally resistant Jimian20 plants quickly showed typical symptoms, such as leaf yellowing, vascular browning and growth retardation, indicating that this gene is indispensable in disease defense. Further analysis showed that after the expression of GhLAC15 was upregulated, the accumulation level of lignin and its synthetic intermediates in cotton increased significantly, accompanied by a large enrichment of secondary metabolites such as flavonoids, which are known to enhance the cell wall barrier function or directly inhibit pathogen activity. GhLAC15 plays a core role in cotton's resistance to Verticillium wilt infection by regulating cell wall structure reinforcement and metabolic defense reactions. Its clear functional pathway and stable expression characteristics give it a high potential for breeding applications, and it is expected to serve as a molecular marker or disease resistance gene resource to serve the breeding of future cotton resistant varieties. 5.2 GWAS-basedGhAMT2 gene resistance research and breeding potential Another representative study discovered the ammonium transporter encoding gene GhAMT2, which is closely related to Verticilliumwilt resistance, through whole genome association analysis and transcriptome integration (Wang et al., 2025). This study used 355 upland cotton materials to evaluate Verticilliumwilt resistance in three consecutive years of multi-point field trials, and combined resequencing data for GWAS analysis. On chromosome A01, the researchers located a QTL region that was strongly correlated with the disease index and identified GhAMT2 as a candidate gene in this segment. In the root tissues of different varieties, GhAMT2 showed an earlier and stronger expression response in disease-resistant varieties, especially within 12 hours after pathogen infection, its expression level increased sharply. This gene has a co-expression relationship with multiple disease resistance-related pathways such as lignin synthesis, salicylic acid signaling, and ROS metabolism, suggesting that it may improve the overall resistance level of plants by regulating the root environment and signaling network. In order to verify the biological function of GhAMT2, the researchers constructed its VIGS silenced plants. The results showed that after silencing treatment, cotton's resistance to pathogens was significantly weakened, the disease index increased, and the leaf wilting rate accelerated. Correspondingly, the study also constructed a transgenic line overexpressing GhAMT2 in Arabidopsis. After inoculation with the pathogen, these plants showed
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