LC-MS/MS Based Label Free Quantitative Shotgun Proteomics Revealed Contrasting Responses of Rice Germplasms towards Salinity and Identified Expression of Redox-Regulatory Proteome

Abstract

Background: High throughput proteomic studies are extremely important in investigating reprogramming of gene expression in plants grown under environmental stress. Though there are plenty of evidences of salt inducible proteins characterized through different proteomic investigations in rice, but scant attentions are paid in identifying salt-responsive proteomes in rice that are involved in redox regulation necessary for combating oxidative stress induced by salinity, and hence is the objective of the present investigation. Results: Imposition of post-imbibitional salinity stress (PISS) to the experimental rice cultivars differing in sensitivity towards salinity (Oryza sativa L., Cultivars Patnai and IR29) in general revealed strong correlation between the parameters of oxidative damages (lipid peroxidation, protein oxidation) and redox status (endogenous level of total ROS, H2O2, and total radical scavenging properties). Cultivar Patnai with better redox-regulatory attributes at metabolic interface under PISS, exhibited better germination phenotypes (T50 value of germination). The level free quantitative shotgun proteomic analysis through LC-MS/MS identified a number of salinity-responsive proteins, whose abundance changes significantly in response to PISS, particularly for the redox competent and tolerant germplasm Patnai. The greater abundance of expressed proteins is associated with the biological, cellular and molecular processes for the tolerant germplasm Patnai grown under PISS in contrast to its counterpart IR29. Comparative GO analysis of separated proteins revealed an abundance of expressed proteins involved in the regulation of redox homeostasis, like ascorbate-glutathione cycle, hydrogen peroxide metabolic process, hydrogen peroxide –responsive proteins, cellular redox homeostasis, hydrogen peroxide signalling proteins etc. Conclusion: Comparative proteomic investigation through LC-MS/MS identified a number of salinity-responsive proteins whose abundance changes significantly under PISS, particularly for the tolerant rice cultivar Patnai, confirming the role of redox-regulatory proteins in redox–regulation at metabolic interface necessary for salinity tolerance.