Proteomic analysis of rose apple reveals defense proteins activated during Lasiodiplodia theobromae infection

Rose apple (Syzygium samarangense) is a highly nutritious tropical fruit with high economic value, but its post-harvest quality is drastically impaired by fungal pathogens, especially Lasiodiplodia theobromae. This experiment used a proteomics method to study the molecular events of the rose apple fruit in response to the infection of L. theobromae. The fruits were separated into control and pathogen-inoculated groups, and protein extraction and separation were performed using two-dimensional gel electrophoresis (2-DE). Proteins that showed a difference in expression were determined by MALDI-ToF/ToF MS/MS and further examined by protein-protein interaction network mapping. Fourteen spots were identified that showed significant variation in their expression between the non-infected and the infected samples. Proteins associated with stress, such as Heat shock protein 90 − 1 and Heat shock 70 kDa protein, were significantly increased, suggesting a possible involvement in cell defence mechanisms. Also, there was a higher expression of Peptidyl-prolyl cis-trans isomerase, which may indicate increased protein folding activity during pathogen stress. Conversely, the downregulation was observed in the Linoleate 9 S-lipoxygenase, which suggests inhibition of fatty acid synthesis during infections. All these results demonstrate that there is extensive translational-level reprogramming of stress adaptation and protein homeostasis in response to fungal invasion. The proteins identified represent potential candidates for future studies aimed at understanding resistance mechanisms in rose apple. Their roles need further functional validation to have a better insight into their roles and to facilitate the development of effective postharvest management strategies.