Proteomic Variation in Two Genotypes of Bitter Gourd During Cold Acclimation

Bitter gourd (Momordica charantia L.) is widely consumed worldwide due to its unique flavor and medicinal value. In subtropical regions, low spring temperatures limit bitter gourd growth, leading to plant mortality and yield loss. Thus, elucidating the mechanisms of cold tolerance in bitter gourd could facilitate the development of cold-resistant cultivars via genetic engineering or molecular breeding. In this study, a cold-tolerant (CT) and a cold-sensitive (CS) inbred line of bitter gourd were used to investigate proteomic differences under cold stress. Before cold stress, 504 differentially accumulated proteins (DAPs) were identified, with 123 up-accumulated in CT plants compared to CS plants. Upon exposure to cold stress, these numbers changed to 388 DAPs (259 up-accumulated in CT) at 6 h and further to 649 DAPs (415 up-accumulated in CT) at 24 h. K-means cluster analysis identified 65 cold-stress response proteins that may contribute to cold tolerance in CT plants, including evm.TU.chr4.3733 (Proline dehydrogenase 1), evm.TU.chr10.115 (Delta(1)-pyrroline-2-carboxylate reductase), and evm.TU.chr10.815 (Calcium-dependent protein kinase 3). Glucose and starch levels remained stable in both CS and CT plants during cold stress, and the baseline concentration of glucose was consistently and significantly higher in CT plants than in CS plants. Before cold stress, proline content was similar in both CT and CS plants. Following 6 h of cold stress, CS plants accumulated significantly higher proline levels than CT plants. This trend, however, reversed after 24 h, with proline content becoming significantly lower in CS plants. Differential protein accumulation between CT and CS plants under cold stress reflects their distinct responses, with core DAPs serving as key functional determinants of enhanced cold tolerance in the CT genotype. This study revealed important proteomic data underlying the cold stress response in bitter gourd.