Antioxidant response and proteomic modulations in Indian mustard grown under salt stress

Productivity of Indian mustard ( Brassica juncea L. Czern. and Coss.) is markedly reduced by salt stress. To develop salt tolerance in this important oilseed crop is a need of the hour. This study, based on analysis of growth parameters and antioxidant profile of fourteen Indian mustard genotypes treated with 50, 100, 150 and 200 mM of sodium chloride, was performed to identify the salt-sensitive and salt-tolerant genotypes. Salinity stress inhibited biomass accumulation and reduced the protein and chlorophyll contents in a dose-dependent manner. The reduction was the highest in genotype Pusa Agrani and lowest in CS-54, depicting their contrasting sensitivity to salt stress. Salt treatments triggered a concentration-dependent overproduction of reactive-oxygen species and a concurrent upregulation of the expression of different antioxidants. Genotype CS-54 showed the least damage and maintained a high antioxidant level with almost each salt treatment, exhibiting its competence to withstand the damage provoked by salinity stress. Genotype Pusa Agrani, on the contrary, depicted a salt-sensitive nature by way of its very high lipid peroxidation and low intensity of antioxidants. These two genotypes were further investigated through gel-based proteomic approach, which resulted in the identification and quantification of 42 salinity-responsive proteins related to different metabolic modifications. Molecular processes, including photosynthesis, redox homeostasis, nitrogen metabolism, ATP synthesis, protein synthesis and degradation, signal transduction and respiratory pathways, have exhibited significant changes. The identified stress-responsive proteins could pave the way to develop salt tolerance in Indian mustard plant, thus sustaining its productivity under salinity.