The Arabidopsis chloroplast protein S-RBP11 is involved in oxidative and salt stress responses.

S-RBP11, a chloroplast protein, which was isolated using activation tagging system, is shown to be the first Arabidopsis small RNA-binding group protein involved in oxidative and salt stress responses. Activation tagging is one of the most powerful tools in reverse genetics. In this study, we isolated S-RBP11, encoding a small RNA-binding protein in Arabidopsis, by salt-resistant activation tagging line screen and then characterized its function in the abiotic stress response. The isolated activation tagging line of S-RBP11 as well as transgenic plants overexpressing S-RBP11 showed increased tolerance to salt and MV stresses compared to WT plants, whereas s-rbp11 mutants were more sensitive to salt stresses. Transcription of S-RBP11 was elevated upon MV treatment but not NaCl or cold treatment. Interestingly, S-RBP11 protein was localized in the chloroplast and the N-terminal 34 amino acid region of S-RBP11 was necessary for its chloroplast targeting. Our results suggest that S-RBP11 is a chloroplast protein involved in the responses to salt and oxidative stresses.