Proteomics approach combined with biochemical attributes to elucidate compatible and incompatible plant-virus interactions between Vigna mungo and Mungbean Yellow Mosaic India Virus

Background: Vigna mungo, a tropical leguminous plant, highly susceptible to yellow mosaic disease caused by Mungbean Yellow Mosaic India Virus (MYMIV) resulting in high yield penalty. The molecular events occurring during compatible and incompatible interactions between V. mungo and MYMIV pathosystem are yet to be explored. In this study biochemical analyses in conjunction with proteomics of MYMIV-susceptible and -resistant V. mungo genotypes were executed to get an insight in the molecular events during compatible and incompatible plant-virus interactions. Results: Biochemical analysis revealed an increase in phenolics, hydrogen peroxide and carbohydrate contents in both compatible and incompatible interactions; but the magnitudes were higher during incompatible interaction. In the resistant genotype the activities of superoxide dismutase and ascorbate peroxidase increased significantly, while catalase activity decreased. Comparative proteome analyses using two-dimensional gel electrophoresis coupled with mass spectrometry identified 109 differentially abundant proteins at 3, 7 and 14 days post MYMIV-inoculation. Proteins of several functional categories were differentially changed in abundance during both compatible and incompatible interactions. Among these, photosynthesis related proteins were mostly affected in the susceptible genotype resulting in reduced photosynthesis rate under MYMIV-stress. Differential intensities of chlorophyll fluorescence and chlorophyll contents are in congruence with proteomics data. It was revealed that Photosystem II electron transports are the primary targets of MYMIV during pathogenesis. Quantitative real time PCR analyses of selected genes corroborates with respective protein abundance during incompatible interaction. The network of various cellular pathways that are involved in inducing defense response contains several conglomerated cores of nodal proteins, of which ascorbate peroxidase, rubisco activase and serine/glycine hydroxymethyl transferase are the three major hubs with high connectivity. These nodal proteins play the crucial role of key regulators in bringing about a coordinated defense response in highly orchestrated manner. Conclusions: Biochemical and proteomic analyses revealed early accumulation of the defense/stress related proteins involved in ROS metabolism during incompatible interaction. The robustness in induction of defense/stress and signal transduction related proteins is the key factor in inducing resistance. The mechanism of MYMIV-resistance in V. mungo involves redirection of carbohydrate flux towards pentose phosphate pathway. Some of these identified, differentially regulated proteins are also conferring abiotic stress responses illustrating harmony amongst different stress responses. To the best of our knowledge, this is the lone study deciphering differential regulations of V. mungo leaf proteome upon MYMIV infection elucidating the mode of resistance response at the biochemical level.