MicroRNA414c affects salt tolerance of cotton by regulating reactive oxygen species metabolism under salinity stress

Salinity stress is a major abiotic stress affecting the productivity and fiber quality of cotton. Although reactive oxygen species (ROS) play critical roles in plant stress responses, their complex molecular regulatory mechanism under salinity stress is largely unknown in cotton, especially microRNA (miRNA)-mediated regulation of superoxide dismutase gene expression. Here, we report that a cotton iron superoxide dismutase gene <i>GhFSD1</i> and the cotton miRNA ghr-miR414c work together in response to salinity stress. The miRNA ghr-miR414c targets the coding sequence region of <i>GhFSD1</i>, inhibiting expression of transcripts of this antioxidase gene, which represents the first line of defense against stress-induced ROS. Expression of <i>GhFSD1</i> was induced by salinity stress. Under salinity stress, ghr-miR414c showed expression patterns opposite to those of <i>GhFSD1</i>. Ectopic expression of <i>GhFSD1</i> in <i>Arabidopsis</i> conferred salinity stress tolerance by improving primary root growth and biomass, whereas <i>Arabidopsis</i> constitutively expressing ghr-miR414c showed hypersensitivity to salinity stress. Silencing <i>GhFSD1</i> in cotton caused an excessive hypersensitive phenotype to salinity stress, whereas overexpressing miR414c decreased the expression of <i>GhFSD1</i> and increased sensitivity to salinity stress, yielding a phenotype similar to that of <i>GhFSD1</i>-silenced cotton. Taken together, our results demonstrated that ghr-miR414c was involved in regulation of plant response to salinity stress by targeting <i>GhFSD1</i> transcripts. This study provides a new strategy and method for plant breeding in order to improve plant salinity tolerance.