Proteomic and metabolic profiling of rice suspension culture cells as a model to study abscisic acid signaling response pathways in plants.

Rice (Oryza sativa cv Taipei 309) suspension culture cells (SCCs) were used as a simple, single cell model system to gain insights into the complex abscisic acid (ABA) signaling response pathways in plants. Following system establishment involving morphological observations and transcript profiling of genes known to be ABA responsive in planta, a comprehensive proteomic and metabolomic study was performed. A total of 759 buffer-soluble proteins that included 3284 peptides categorized into 656 protein families are reported. Using iTRAQ, only 36 of these proteins showed statistically significant changes in abundance in response to ABA. In addition, a GC-MS based metabolite profiling study allowed the identification of 148 metabolites that included 25 amino acids (AAs), 45 organic acids (OAs), 35 sugars, 19 fatty acids, 2 polyamines, 4 sterols, 5 sugar acids, 4 sugar alcohols, and 9 miscellaneous compounds. Of these, only 11 (8.8%) changed in a statistically significant manner in response to ABA treatment. These studies provide important insights into plant responses to ABA at the protein and metabolite level.