Over-expression of osa-MIR396c decreases salt and alkali stress tolerance.

Salt and alkali stress are two of the main environmental factors limiting rice production. Thus, understanding the mechanisms of salinity and alkali stress tolerance is necessary to modify rice to increase its resistance to salinity and alkaline stress. MicroRNAs (miRNAs) are approximately 21-nucleotide RNAs that are ubiquitous regulators of gene expression in eukaryotic organisms. In plants, miRNAs constitute one of five classes of small RNAs that function primarily as negative regulators for gene expression at the posttranscriptional level. Several plant miRNAs, such as miR396, play vital roles in plant growth, development and resistance to stresses. In this study, we identified osa-MIR396c, which shows dramatic transcript change under salt and alkali stress conditions in Oryza sativa. We designed an experiment to detect miRNA-target interaction and demonstrated that several transcription factors related to growth, development, and stress tolerance are targeted by osa-MIR396c. Transgenic rice and Arabidopsis thaliana plants constitutively over-expressing osa-MIR396c showed reduced salt and alkali stress tolerance compared to that of wild-type plants. Overall, this study further established a link between salt and alkali stress and osa-MIR396c in rice.