mi R 408 is involved in abiotic stress responses in Arabidopsis

Abstract

Summary: Micro RNA s (mi RNA s) are small RNA s that regulate the expression of target genes post‐transcriptionally; they are known to play major roles in development and responses to abiotic stress. mi R 408 is a highly conserved mi RNA in plants that responds to the availability of copper and targets genes encoding copper‐containing proteins. It was recently recognized to be an important component of the HY 5–SPL 7 gene network that mediates a coordinated response to light and copper, illustrating its central role in the response of plants to the environment. Expression of mi R 408 is significantly affected by a variety of developmental and ‏environmental conditions; however, its biological function is ‏unknown. Involvement of mi R 408 in the abiotic stress response was investigated in A rabidopsis. Expression of mi R 408, as well as its target genes, was investigated in response to salinity, cold, oxidative stress, drought and osmotic stress. Analyses of transgenic plants with modulated mi R 408 expression revealed that higher mi R 408 expression leads to improved tolerance to salinity, cold and oxidative stress, but enhanced sensitivity to drought and osmotic stress. Cellular antioxidant capacity was enhanced in plants with elevated mi R 408 expression, as manifested by reduced levels of reactive oxygen species and induced expression of genes associated with antioxidative functions, including C u/Z n superoxide dismutases (CSD 1 and CSD 2) and glutathione‐S‐transferase (GST‐U 25), as well as auxiliary genes: the copper chaperone CCS 1 and the redox stress‐associated gene SAP 12. Overall, the results demonstrate significant involvement of mi R 408 in abiotic stress responses, emphasizing the central function of mi R 408 in plant survival.