Roles of miRNAs in Nutrient Signaling and Homeostasis

In natural environments, plants frequently have to cope with insufficient nutrient supply, which significantly impairs crop yield. Nutrients have to be optimally distributed to permit the best possible growth and reproduction. To react to nutrient deficiencies, plants have evolved a broad spectrum of diverse metabolic, physiological and developmental adaptations. The amount and availability of different nutrients has to be monitored in individual cells and organs, and information about the nutrient status has to be communicated over short and long distances. Recent studies have shown that specific miRNAs are important components of plant responses to nutrient starvation. miR395, positively responsive to sulfur starvation, miR398, induced by low copper and sucrose, and miR399, induced by phosphate deficiency, are among the best studied nutrient-dependent miRNAs. This chapter will summarize current knowledge about the functions of these miRNAs under different nutrient deficiencies, and the possible contribution of miRNA-based regulation to maintaining nutrient homeostasis.