Advances on the study of microRNA-mediated responses to nutrient stress in legume crops

MicroRNA (miRNA) is one kind of non-coding small RNA (sRNA), and has 20-24 nucleotides in length, and plays important roles in plant growth development and in response to biotic and abiotic stress. Many evidences have shown that miRNA is crucial modulator in adaptations of plant to nutrient stress. Legume plants could fix nitrogen from atmosphere and provide proteins as well as edible oil for human being. Nutrient stresses in soils obviously inhibit legume growth and development, and result in a decrease in yield. In past decades, most studies on mediation roles of miRNA in responses to nutrient stresses in Arabidopsis and rice have been characterized, respectively. However, recent studies have witnessed emerging reports on the functions of miRNA in response to nutrient stress in legumes, and revealed crucial roles of miRNAs in adaptations of legumes to various adverse nutrient conditions via modulating activity of target genes such as sensing alteration of nutrient status and fine-tuning nutrient homeostasis. In this review, the regulation role of miRNAs in response to different nutrient stresses was reviewed, especially in response to the stresses from phosphorus (P), nitrogen (N), sulphur (S), iron (Fe), copper (Cu) deficiencies and calcium (Ca) toxicity, and the mechanisms of miRNAs involved in the adaptations of legume to different kinds of nutrient stress were discussed, and the perspective of research on nutrient-related miRNA in legume was outlined in the near future.