Roles of Long-Distance Signals in Nitrogen, Phosphorus, and Sulfur Uptake and Sensing in Plants

Plants must adapt to climate changes because they are rooted in place. Climate changes greatly affect the soil environment, sometimes reducing the nutrient content. Plants require 17 essential elements for healthy growth and development. Among these, nitrogen, phosphorus, and sulfur are macroelements required for the biosynthesis of primary and secondary organic metabolites, such as proteins and nucleic acids, and for the maintenance of photosynthetic activity. Under nitrogen, phosphorus, or sulfur deficiency, plant growth is suppressed, resulting in poorer crop yield. Thus, to avoid the risk of climate changes to food production, it is important to understand how plants adapt to their environment in response to inorganic nutrient deficiency. Plant roots directly contact the soil environment, but the mechanism by which the amount of inorganic nutrients is recognized is complicated. Plants can accurately perceive the nutrient levels in soil and use this information to change their architecture and expression of nutrient transporters and to enhance plant-microbe interaction in the rhizosphere through shoot-to-root or root-to-shoot transportable signals such as plant hormones and microRNA. In this chapter, we summarize the roles of auxins, cytokinins, and strigolactones as long-distance signals in the pathways involved in nitrogen, phosphorus, and sulfur uptake and sensing and in signaling pathways.