Over-expression of miR397 improves plant tolerance to cold stress in Arabidopsis thaliana

Cold stress is an environmental factor that limits the geographical distribution and growing season of plants. The plant response to cold involves different metabolic pathways and gene regulation. Although the expression of some miRNAs is significantly altered in cold stress, little is known about the regulatory function of miRNAs in plant resistance to cold. In this study, we generated transgenic Arabidopsis plants which harbor an over-expression construct of 35S::miR397a. Analysis by RNA blotting revealed high levels of miR397a transcripts in the transformed plants. Plant cold tolerance assays demonstrated that over-expression of miR397a improved plant tolerance to chilling and freezing stresses. In addition, this study showed that the freezing tolerance of miR397a-ov plants was improved by cold acclimation at 4°C. Northern blot analysis revealed that overexpression of miR397a affected the expression of coldregulated CBF genes and downstream COR genes. These findings provide evidence demonstrating a regulatory role of miR397 in the cold signaling pathway and plant tolerance to chilling and freezing stresses.