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

The Asian citrus psyllid, <i>Diaphorina citri</i>, transmits the putative causal agent of citrus greening disease, '<i>Candidatus</i> 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 <i>D. citri</i> proteins that specifically recognize membrane proteins of '<i>Ca.</i> L. asiaticus'. Whole-body protein extracts of <i>D. citri</i> were separated by electrophoresis and blotted onto polyvinylidene difluoride (PVDF) membranes. The membranes were overlayed with sonicated leaf midrib extracts from '<i>Ca.</i> L. asiaticus'-infected citrus plants. The protein complexes were detected using different antibodies against '<i>Ca.</i> 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 '<i>Ca.</i> L. asiaticus'-<i>D. citri</i> interactions. Understanding the pathogen-vector interactions will lead to better-designed control strategies based on the interference with specific interactions and/or blocking transmission.