Identification of Diaphorina citri Proteins with Affinity to ‘ Candidatus Liberibacter asiaticus’, the Putative Pathogen of Citrus Greening Disease

The Asian citrus psyllid, Diaphorina citri, transmits the putative causal agent of citrus greening disease, 'Candidatus Liberibacter asiaticus'. The transmission occurs in a propagative circulative manner. Specific protein-protein interactions are required for the accomplishment of the transmission process. We employed the far-Western technique, also known as protein overlay assay, and mass spectrometry, to identify D. citri proteins that specifically recognize membrane proteins of 'Ca. L. asiaticus'. Whole-body protein extracts of D. citri were separated by electrophoresis and blotted onto polyvinylidene difluoride (PVDF) membranes. The membranes were overlayed with sonicated leaf midrib extracts from 'Ca. L. asiaticus'-infected citrus plants. The protein complexes were detected using different antibodies against 'Ca. L. asiaticus' membrane proteins and peptidoglycans associated with lipoproteins. By comparison, spots were extracted from a polyacrylamide gel for LC-MS-MS analysis. Identified proteins included ATP synthase alpha and beta subunits, actin, alpha- and beta-tubulins, transitional endoplasmic reticulum ATPase TER94, 78 kDa glucose-regulated protein, and arginine kinase. These findings emphasized the involvement of energy machinery and muscle proteins in the 'Ca. L. asiaticus'-D. citri interactions. Understanding the pathogen-vector interactions will lead to better-designed control strategies based on the interference with specific interactions and/or blocking transmission.