s Proteomic Investigations to Assess the Impact of Salinity on Vigna radiata L. Genotypes

Background: In our previous study, six cultivars of Mungo (Vigna radiata) were exposed to 100-250 mM NaCl and studied for changes in growth and biomass. Among them, AEM-96 cultivar of the Mung bean [Vigna radiata (L.) Wilczek cv.] was found to tolerate NaCl stress at 250 mM. Objective: The soluble proteome of salt-tolerant mungo cultivar (AEM-96) was compared to the proteome of control mungo to investigate the possible mechanism of salinity tolerance. Methods: Gel-based two-dimensional gel electrophoresis was employed for comparative proteomics. PDQuest-based image analysis of 2D SDS-PAGE was performed. Scatter plots were prepared and total spots were analyzed for 2-fold changes in abundance of protein spot intensities in control and treated gels. Results: In total 517 protein spots were detected; 36 with high significance. Among these 36 spots, 2-fold expression change was analyzed in 27 protein spots. Seven protein spots were upregulated, eight spots were down-regulated, 3 spots were newly induced and 9 spots were silenced, while 9 protein spots did not change their 2-fold abundance under salinity. Protein spots (9 in total) which were 2-fold upregulated and newly induced were excised from the respective gels. The spots were tryptically digested and run on LC-MS/MS for generating peptides and performing a comparative fingerprinting of the proteins. The peptide signal data was loaded on the Mascot (Swissprot) database to retrieve protein IDs. Proteins with the best score were selected, namely isomers of oxygen- evolving enhancer protein 1 (S1-S3), RuBisCO (S4), oxygen-evolving enhancer protein 2 (S5), Heat shock protein 70 isomers (S6-S7), RuBisCO activase (S8), rubber elongation factor (S9) and pathogen-related protein 10 (S10). Conclusion: The identified proteins were found to play important roles in photosynthesis, stress response and plant growth.