Proteome Insights into the Watercore Disorder on Pineapple Discovered Resistant Germplasm-Specific Accumulation of Cell Wall-Modifying and Defense Proteins

Watercore disease, a physiological disorder in pineapple (Ananas comosus), manifests during late fruit development. Affected fruits develop water-soaked flesh and reduced storability. (1) Background: To explore underlying molecular mechanisms, comparative proteomic profiling was conducted in this study. (2) Methods: Data-independent acquisition (DIA) strategy was employed for comparative analysis between the resistant germplasm “35-1” and the susceptible germplasm “29-3”, as well as between the healthy and diseased “Paris”. (3) Results: Resistant (“35-1”) versus susceptible (“29-3”) germplasm analysis revealed differentially expressed proteins (DEPs) and unique proteins (SEPs) enriched in cell walls, secretory vesicles, and apoplast, functioning in cell wall loosening, hormone response, isoflavonoid biosynthesis, and farnesyl diphosphate biosynthesis. Healthy versus diseased “Paris” pulp analysis showed DEPs/SEPs enrichment in ribosomal small subunit biogenesis. These proteins form a central regulatory network potentially orchestrating tRNA synthesis, tubulin biosynthesis, and other carbohydrate metabolism. Partial protein overlap occurred in germplasm- and disease-derived differences. Resistant germplasm (“35-1”) and healthy “Paris” accumulated stress-responsive/resistant proteins and cell wall-modifying enzymes (e.g., phenylalanine ammonia-lyase, raffinose synthase, expansins, and mannan hydrolase). Susceptible germplasm (“29-3”) and diseased “Paris” exhibited prominent stress-responsive protein accumulation, such as alcohol dehydrogenase, 1-aminocyclopropane-1-carboxylate oxidase, and hypoxia-induced protein. (4) Conclusions: This comparative proteomics study identifies pineapple watercore resistance/susceptibility-associated proteins, providing a molecular basis for resistant germplasm development and disorder control.