Nutrient- and other stress-responsive microRNAs in plants: Role for thiol-based redox signaling.

Now it is well recognized that the microRNA (miRNA) expression is altered in response to internal (developmental or hormonal) or external stimuli such as biotic and abiotic stresses in plants. It is also known that several miRNAs are induced in response to deficiency of specific nutrients within the plant or in the external sources, i.e., soil/nutrient media. For instance, P-deprivation induces miR399, S-deprivation induces miR395 and Cu-deprivation induces miR398, miR397 and miR408 in several plant species. Although the transcription factors (PHR1, SLIM1 and SPB7) that regulate these nutrient-deprivation inducible miRNAs have been identified but the upstream biochemical pathway that activates them is relatively unknown. In a recent study, we demonstrated for the first time that redox signaling plays a critical role in S-deprivation-inducible miR395 expression in Arabidopsis. In this short review, we draw additional hypotheses for the involvement of redox signaling and/or reactive oxygen species (ROS) signaling in inducing other nutrient or stress-responsive miRNAs in plants.