Productivity of rapeseed (Brassica napus L.), the third most important oilseed crop, was reduced more than other crops under the salt stress higher than the threshold. Thus, breeding, especially at seedling stage, seems necessary. Plants under salt stress, by synthesis of essential metabolites, specific structural proteins or enzymes of metabolic pathways deal with the stress. To identify the molecular mechanisms of salt responsiveness in rapeseed, ‘Option500’ a salt-sensitive genotype was exposed to 0, 150, and 300mM NaCl during the seedling stage. An increase in proline and the Na+ content of leaf and a reduction in shoot dry weight, plant height, K+ content and K+/Na+ ratio were observed. Protein expression changes were examined by two-dimensional electrophoresis (2-DE). Out of 110 protein spots identified by 2-DE gels, 37 spots showed significant abundant changes based on induction factor (IF), and 7 spots were recognized significantly at 5% probability level, which 1 and 6 spots were up and down-regulated, respectively. By using LC-MS/MS mass spectrometry analysis, proteins were identified which are involved in energy production and photosynthesis. Activity of enzymes involved in energy production decreased under stress, while the abundance of Phosphoribulokinase (PRK) -an important enzyme in the pentose phosphate pathway- increased.

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