Uridine Kinase-like Protein (GhUKL4) Positively Regulates Resistance to Verticillium Wilt in Cotton

<b>Background:</b> Verticillium wilt (VW), caused by the fungal pathogen <i>Verticillium dahliae</i>, is a destructive disease that severely compromises cotton yield and fiber quality. Pyrimidine nucleotides, as essential metabolites and nucleic acid components, play critical roles in plant development and stress responses. However, genes involved in pyrimidine metabolism, especially their roles in disease resistance, remain largely uncharacterized in plants. <b>Methods:</b><i>Ghir_D05G039120,</i> a gene encoding uridine kinase, shown to be associated with VW resistance in our previous study, was cloned and named as <i>GhUKL4</i>. The differential expression of <i>GhUKL4</i> between the resistant and susceptible cultivars at multiple time points post-inoculation with <i>V. dahliae</i> was analyzed by quantitative real-time PCR (qRT-PCR), and the uracil phosphoribosyl transferase (UPRT) and uridine 5'-monophosphate kinase (UMPK) domains were verified by analyzing the amino acid sequences of <i>GhUKL4</i>. The role of <i>GhUKL4</i> in the defense against VW infection was estimated by silencing <i>GhUKL4</i> in the resistant and susceptible cultivars using virus-induced gene silencing (VIGS) analysis. <b>Results:</b> There were significant differences in the expression level of <i>Ghir_D05G039120</i>/ <i>GhUKL4</i> among resistant and susceptible cotton lines. GhUKL4 contains UPRTase and UMPK domains, and there was one SNP between the resistant and susceptible cultivars in its 3'-UTR region. The silencing of <i>GhUKL4</i> reduced cotton's resistance to VW through mediating hormone signaling (JA) and oxidative stress (ROS) pathways. <b>Conclusions:</b> GhUKL4, encoding UMPK and UPRTase domain proteins, is a new regulatory factor associated with VW resistance in <i>Gossypium hirsutum</i> through fine-tuning JA-signalling and ROS bursting.