Enhanced salt tolerance of rice seedlings by abscisic acid (ABA) pretreatment was observed from phenotypic and physiological analyses. Total proteins from rice roots treated with ABA plus subsequent salt stress were analyzed by using proteomics method. Results showed that, 40 protein spots were uniquely upregulated in the seedlings under the condition of ABA pretreatment plus subsequent salt stress, whereas only 16 under the condition of salt treatment. About 78% (31 spots) of the 40 protein spots were only upregulated in the presence of the subsequent salt stress, indicating that plants might have an economical strategy to prevent energy loss under a false alarm. The results also showed that more enzymes involved in energy metabolism, defense, primary metabolism, etc. were upregulated uniquely in ABA-pretreated rice seedlings, suggesting more abundant energy supply, more active anabolism (nitrogen, nucleotide acid, carbohydrate, etc), and more comprehensive defense systems in ABA-pretreated seedlings than in salt stressed ones.
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