Transcriptome analysis reveals key immune pathways and metabolites associated with resistance to <i>Verticillium dahliae</i> in <i>GbMBL1.1A</i> ‐overexpressing cotton

Cotton (Gossypium barbadense L. and Gossypium hirsutum L.), a major economic crop, suffers severe yield losses due to Verticillium wilt caused by Verticillium dahliae Kleb. Although the lectin receptor-like protein GbMBL1.1A has been identified as a key activator of hypersensitive cell death in cotton resistance to this pathogen, its downstream defense mechanisms remain unknown. Here, we performed comparative transcriptome analyses between the GbMBL1.1A-overexpressing (OE) cotton line and its wild-type (WT) recipient counterpart (WC) under both normal (non-infected) and V. dahliae infected conditions. A total of 760 differentially expressed genes (DEGs) were identified by comparing GbMBL1.1A-OE and WT cotton lines under normal condition. Upon pathogen infection across three timepoints, the counts of 1679 (1063 up, 616 down) and 1648 (633 up, 1015 down) DEGs were identified uniquely from GbMBL1.1A-OE or WT cotton line, respectively, relative to their mock controls. Further analysis of these DEGs revealed three aspects of changes due to GbMBL1.1A overexpression: (1) Pre-infection priming via selective pattern recognition receptor modulation, mitochondrial cell death activation, and reactive oxygen species antioxidant perturbation under normal condition; (2) Significant enhancement of plant defense against pathogen through the remodeling of immune receptor activity, alteration of signal transduction and regulation, and modulation of secondary metabolic processes, with the most significant alteration occurring in lignin and phenylpropanoid metabolism. (3) Dynamic redox homeostasis regulation through metabolite interconversion enzymes during infection process. Collectively, these findings strengthen the theoretical foundation and provide novel candidate targets for developing improved control strategies to enhance cotton resistance against V. dahliae.