Agricultural practices determine world food supply and, to a great extent, the state of the global environment because of their influence on ecosystems and the inputs of nutrients including nitrogen (N) and phosphorus (P). Intensive crop production has resulted in environmental pollution and soil acidification due to excessive application of nitrogen fertilizers. So if we could get an increased understanding of the physiological and genetic regulation of plants response to low-nitrogen (LN) stress, we might be able to develop new crop varieties with increased nutrient-use efficiency through LN tolerance.
MicroRNAs (miRNAs) are small [approx. 21 nucleotides (nt)] endogenous RNAs that can play key regulatory roles in plants and animals by targeting mRNAs for cleavage or translational repression. miRNAs help plants sense and reduce nutrient stresses such as phosphate, sulfate and copper. Nitrate is a major form of inorganic N taken up by cereal crop roots. A recent paper in Annals of Botany identifies miRNAs and their targets in maize (Zea mays) subjected to low-nitrogen stress. Of 85 potentially new miRNAs, 25 show a more than two-fold relative change in response to low-nitrogen compared to optimal conditions. This increases our understanding of the physiological basis for low-nitrogen tolerance and adaptation in maize. Increasingly, systems biology approaches such as whole-scale miRNA analysis can accelerate our integrated knowledge of plant biology through such discoveries as this.