Cotton Genomics and Genetics 2025, Vol.16, No.6, 278-289 http://cropscipublisher.com/index.php/cgg 282 In the experiment, two-dimensional gel electrophoresis (2-DE) combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to track these changes. In the early stage of infection, disease-related proteins (PR) and various antioxidant enzymes are rapidly activated, and components related to the phenylpropanin metabolic pathway are also upregulated, indicating that the basal defense is almost an instantaneous response. As the disease progresses, the number of proteins involved in signal transduction, protein folding and secondary metabolism keeps increasing, indicating that cotton cells gradually establish a coordinated defense system under continuous stress. This proteomic remodeling over time is not a simple "enhancement", but rather a trade-off and balance: on the one hand, maintaining energy supply and cellular homeostasis, while on the other hand, it is necessary to limit the spread of pathogens. The performance of CRI 12 indicates that it achieves a dynamic integration between constitutive and inducible defense, making the defense response both timely and not excessive (Xing et al., 2024). 4.2 Key findings From the proteomic changes of CRI 12, several key aspects of the confrontation between cotton and pathogens can be observed. The first is the activation of defense proteins. PR proteins such as chitinase, β-1, 3-glucanase and sweet proteins accumulate in large quantities. They can destroy the cell walls of fungi and at the same time strengthen the host's own barrier. Secondly, the full activation of the antioxidant system is also very obvious. The increased expression levels of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) indicate that the reactive oxygen species (ROS) levels are strictly controlled to reduce cellular oxidative damage and maintain reducing balance. Meanwhile, the primary metabolism has shown a "stepping aside" phenomenon. The proteins related to photosynthesis and carbon metabolism decline, and energy and resources are redistributed to the defense direction to support the synthesis of lignin and flavonoids. The secondary metabolic pathways were significantly activated, and enzymes such as phenylalanine ammoniase (PAL) and chalketone synthase (CHS) were enhanced in expression, providing raw materials for structural reinforcement and the accumulation of antibacterial substances (Xiao et al., 2023). The dynamic changes of signals and folding proteins should not be ignored either. Calcium-binding proteins, heat shock proteins (HSP70, HSP90), and 14-3-3 proteins accumulate differentially at different stages. These molecules are involved in stress signal transduction and regulation of protein folding homeostasis, and are important nodes for maintaining the orderly operation of the defense network (Figure 2) (Zhou et al., 2022). Figure 2 FLiC induces Ca2+ production in upland cotton epidermal cells. (A) FLiC induces increased intracellular Ca2+ content. (B) Intracellular Ca2+ quantification. The data represent the means ± SDs; n = 3. One-way ANOVA (p < 0.05) followed by Duncan’s test was used for multiple comparisons. The different letters indicate significant differences at the 0.05 probability level. Bars = 50 μm (Adopted from Zhou et al., 2022)
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