The mir390-GhCEPR2 module confers salt tolerance in cotton and Arabidopsis

Global crop production is challenged by increasing severity of soil salinization that is exacerbated by the accelerated climate change and agricultural activities. Recently, studies have found that microRNAs (miRNAs) play an important role in response to abiotic stresses, including soil salinity. In our previous studies, we identified cotton mir390a/b/c (ghr-mir390a/b/c) that are responsive to salt stress. In the current study, GhCEPR2 was identified as a target gene of ghr-mir390 that responds to salinity stress. We propose a novel regulatory module comprising ghr-mir390 and GhCEPR2, which was examined by degradome sequencing and verified by 5'RLM-RACE and transient expression in Nicotiana benthamiana. Transgenic over-expression of GhCEPR2 in both Arabidopsis thaliana and cotton led to enhanced tolerance against salinity stress, accompanied by rising proline content and reduction in malondialdehyde concentration. On the other hand, over-expression of ghr-mir390 resulted in increased sensitivity to salt stress, consistent with the observation in GhCEPR2-silenced cotton. A number of key genes involved in ABA- and salt tolerance-related signaling pathways were found to be up-regulated by ghr-mir390a, but inhibited by GhCEPR2 phosphorylation. Overall, our study may broaden and deepen our understandings on the effect of the ghr-mir390-GhCEPR2 module in regulating cotton salt tolerance.